Exercise for the Human Knee, Part III

109 comments written by Joshua Trentine

Exercise for the Human Knee
Part III

by Ken Hutchins

Note: This material is excerpted from a more-complete chapter in
The Renaissance of Exercise—Volume II (ROE-II) by Ken Hutchins.

Some History

I gathered most of the following information—regarding the Nautilus cam profiles—in 1986 just after Arthur Jones sold Nautilus to the Ward Group of Dallas. The new owners were considering modification of the resistance curves on the Nautilus machines, but there was a big problem. There was no documentation of these curves. No one knew what they were (to begin with), and the only way to get this information was for me or Clay Steffee or Gary Jones to perform tedious measurements. We were the only remaining people knowledgeable to perform cam take-off measurements. Clay and Gary rehired me back into the company specifically to perform this task, because Clay did not have the time to do it, and Gary was leaving the company.

Measuring the instant levers from a cam with respect to its position is relatively easy, but almost every engineer in the fitness industry performs this incorrectly. When I worked for Nautilus, I was amazed at the profound ignorance surrounding this simple technique. And I never accept the measurements of others unless I witness their procedure. In ROE-II I will explain this in detail, but for now I only compare some curves from some knee extension machines.


As I announced in Part II, my purpose herein is to expose the worst offenders of excessive load as the knees approach complete extension in a knee extension device. And as I accuse, the shear talkers—while unable to clearly substantiate that internal loads on the cruciates become excessive during such exercise—are largely ignorant of the loads provided externally by various equipment and exercise modalities, including the ubiquitous knee-setting.


To compare curves, I use several expressions. If I say that a curve portrays a “12:1 fall-off,” this indicates that its largest instant lever is 12 times greater than its smallest. This expression does not necessarily indicate where in the range of motion the greatest and smallest reside, but a ratio this large usually assumes that the top of the positive excursion is the location of least resistance.

The blatant exception to the last statement is that the X-Force Leg Quadriceps machine somewhat decreases as complete knee extension is attained and then increases approximately 40 % when the subject pauses at completion.

If I say that, “the ratio is 1:12,” I indicate that the resistance is the opposite of a fall-off. It is an increase. And note that this example is not a realistic occurrence. I don’t believe that I have seen such drastic increase, although the negative cam in the vintage Nautilus Duo Squat was theoretically capable of this, and I never measured the production machine.

A 12:1 fall-off is a large fall-off, but note that 13:1 or 14:1 or 15:1 does not impress me as being much more.

My opinion and perception: Meaningful changes are likened to f-stops on a camera lens aperture. Really meaningful steps are doublings of light—or in this case, doublings of ratio. Hence, a meaningful increase in fall-off from 12:1 is probably going to be 24:1 or at least half that change (18:1—half-steps).

Two Major Cam Classes. There are three cam classes used in exercise equipment. The only pertinent ones here are the positive cam and the negative cam.

The positive cam winds-on the drive belt, chain, or cable during positive excursion, and its increase of instant lever length is directly proportional to the load increase placed on the body. It is most useful for portraying resistance decrease especially an accelerating decrease.

A negative cam winds-off the drive belt, chain, or cable during positive excursion, and its increase of instant lever length is directly proportional to the load decrease placed on the body. It is most useful for portraying resistance increase especially an accelerating increase.

I can easily design and make fall-offs of tremendous ratio. I do this by decreasing the instant lever of a positive cam to values close to zero. I could go to zero (or beyond); however, the system requires a minimum of lever to overcome the minimal friction in the machine to make the weights come back down from the position of minimum lever. At this exact point (assuming correct timing of the minimum lever), the musculature will have adequate load merely by squeezing hard into its own tissues, but there resides a possibility that the weights stick at the top of their travel once the subject comes out of the so-called squeeze. Such extreme minimum levers are therefore to be avoided.

When complaining about the lack of adequate fall-off in the early Nautilus Leg Extension models, engineers sometimes replied to me that, “Our newest designs are going to be made to fall off an additional 15-20%,” or something to this effect. Eventually, I came to understand that this meant practically nothing. If the Series III Leg Extension portrayed a fall-off of only 30%—ratio = 10:7—then the additional 20% was of the 30%, an imperceptible change. This merely changed the 30% to 36% when truly meaningful percentile changes would be to 60% then to 120% then to 240%—i.e., doublings.

Granted, sometimes these miniscule improvements seemed palpable, but this appearance was because the friction in the machine was lessened with the incorporation of bearings in the later models.

Also note that when we trained on the Super Leg Extension for several years at an increase of nearly 50%, a round drive wheel—hence, no cam—would seem to have a decrease. Therefore going from the Super’s 1:1.45 ratio to the Series III’s 10:7 ratio seemed a tremendous improvement. And in some ways it truly was.

Also, it is of paramount importance to place the statements and cam-design philosophy of these engineers in the context of their personal movement speed in the equipment. I have never seen a Nautilus engineer who trained properly with respect to the speed of movement. In fact, they often exhibit the most violently fast behavior, while it is impossible for anyone performing excursions faster than about eight seconds to be truly perceptive of and sensitive to the details requiring much attention.

And I must acknowledge that my movement speed—back in the 70s and early 80s at Nautilus—was far too fast.


So I set about to collect all the pertinent information. First, I gathered all the Nautilus models—past and present—of all the machines I could find.

Then I collected all of the latest production cams as well as old ribbed production cams if they were to be had. In some cases I had to use cams that I removed from complete machines after I had marked their timing positions.

Then I precisely reproduced the geometry of each cam and its redirectional sprocket on a large vertical plywood mount so that I could rotate and lock them relative to joint positions in five-degree increments. The instant levers (in inches) are the data in the following four plots that took me several months to complete with the addition of 15 other machines (plots).

Note the symbol (arrow points at each end of a vertical line) I used to denote the location on the curve where knee extension typically ended (or started) although the cam profile that I measure extended somewhat beyond that point.

Note that I dated and initialed each of these plots.

The Nautilus Leg Extension-1

To begin, I feature what I believe to be the Leg Extension-1 (LE-1). This machine vintage was ~1973-1976. Note that the resistance steadily increases throughout the positive. Note that I designated “0” position as the machine start position, not anatomical position.

Its ratio is 1:1.44—an increase of nearly 50%.

The LE-1 is interesting to me for its distinctive counterweights. Since the movement arm was eccentric, it required counterweighting. Hence the larger club, integral with the remote workbox (cam, rear drive wheel, and counterweights), cancels this eccentricity.

The cam itself also is eccentric and the smaller club, integral with the workbox, cancels its eccentricity.

Therefore, these eccentric bodies—the movement arm and the cam—were originally treated as independent components of the system. Contrast this to the naked LE-2 pictured later, and note that it possesses only one counterweight. This counterweight was used to cancel the entire system (instead of separate components of the system). Two counterweights are now deemed unnecessary, and one is regarded as more elegant.

The caption boxes will explain most of the other features of the equipment.

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The X-Force Leg Extension (Leg Quadriceps)

Some readers will expect my assessment of the X-Force Leg Extension. I have not directly measured its instant levers, but I have seen photos and videos of its cam. I estimate that its fall-off is similar to the MedX and Nautilus Series III. So if my assessment is correct, and if the subject reaches the top of the positive, and is then dumped on with a 40% greater load, I consider this quite an egregious offense to the cruciates.

Refocusing the Purpose

Within the depth and scope of the foregoing information, it is easy to lose focus with the purpose of this presentation.

And although the depth and scope of this information is far greater than what anyone else has ever presented, I am not providing complete information herein to perform knee rehabilitation as we at RenEx will eventually do. Nor is my purpose with this information to teach cam design, cam takeoff measuring and plotting, friction analysis, or a host of additional and related subjects. To do justice to any of these topics requires much more detail.

The focus here is that the shear talkers warn of offensive force to the cruciates with a so-called open-chain exercise such as a knee extension device. And they scream alarm without knowing how the externally applied loads are changing relative to the knee’s position. If the shear talkers are correct, it is an astronomical accident, not scientific method.

Assessing Cruciate Threat

I present the following table with some accurate load ratios due to changing instant lever. Some others denoted by “~” are my estimates.

My personal opinion as to their offensiveness (threat) to the cruciates is ranked in the column to the right. This ranking is on a scale of 0-10 with “0” as an indication of “no threat” and “10” as a “worst threat.” On such a scale, “5” represents a “moderate threat.”

“Threat” might be interpreted in several ways depending on the context. Obviously, such rankings are more serious when applied to subjects with knee derangements or those post-operatives. However, we should not ignore these rankings with respect to a normal knee.

I might ask, “How affected are my knees now due to their routine exercise on the Nautilus Super Leg Extension (SLE) 30 years ago?”

I might also pose, “And how do we appraise the SLE when Nautilus so successfully rehabilitated so many subjects—including Eric Soderholm—so far beyond the expectations of conventional physical therapy on such equipment?”

And as Doug McGuff, MD, has recently stated, “… However, kneecaps are not flying off around the country… ”

Still, I don’t want my knees or those of my associates and clients exposed to such unnecessary forces. And we have progressed forward with protocol as well as equipment design that widens the safety margin tremendously since our initial forays into this domain.

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General Recommendations

I don’t believe that there is any reason to question the usefulness of the knee extension exercise in most knee rehabilitation. In fact, I consider that the ideal approach to rehab after most knee surgeries is to place the RenEx Leg Extension next to the hospital bed so that that patient can forego much of the early the knee-setting and possess more precise range and load control. And it is ridiculous to crusade against knee extension exercise in almost any other application for general strengthening. And this applies equally to that feared last 15-30 degrees of extension.

I assert all this with the understanding that I demand a 10/10 protocol. Without such speed control, most of these comparisons, if not all, are moot. I declare that this protocol speed is the most fundamental aspect of all of biomechanics and without its adherence a conversation about much else is pointless.

For now, I merely give you the practical approach to sorting out when and when not to do either knee extension or leg press or both of these exercises. The rule is: If it hurts, don’t do it.

There are many different conditions of the knee. And it is somewhat unusual to find a knee that is perfectly asymptomatic as a subject advances with age. Some of these conditions respond positively to both knee extension and leg press. Some respond somewhat negatively to one or the other.

Some conditions allow one or the other of the two exercises only if they are preceded by a lubrication procedure performed in a knee extension machine. This is merely a slow movement—at least with extension and sometimes with flexion—with a minimal load to slosh synovium around on the articular surfaces before performing serious exercise.

And the worst conditions respond negatively to both exercises under any conditions.

When faced with the worst response to either or both exercises, it is a challenge to find a workable way to load the musculatures. Fortunately, we have a host of options between the two exercises as we strive to avoid joint pain. They include but are not limited to pinning off for pain-free range of motion, lubrication procedures (already mentioned), static protocols with precise force feedback and recording at the magnitude of the slightest pain, and dynamic protocols utilizing perfectly timed loading. Our arsenal in this regard is vast especially when placed in the context of the mechanical controls we have with the RenEx equipment.

As stated many times over, the exact application of these techniques is far beyond the scope of a blog post, but I hope these few words provide an insight into the information explosion that is occurring within our ranks.

In Part IV, I will give the shear talkers a possible solution to their fears—the coupled movement arm. And as Arthur Jones—the king of bombast—might have said, “Just wait, we haven’t unloaded the heavy ordinance on you yet. The big bombers are on the way!”



{ 109 comments… read them below or add one }

avatar mark March 5, 2013 at 6:27 pm

This leads me to believe that, in the absence of a SSS or RenEx LE, static contraction’s best for knee rehab. I requested fully-extended-position statics on the MedX at my facility. I thought I was bypassing a painful segment of my knee’s range. It never occurred to me the the full-range work on the MedX might have -caused- that pain!


avatar Joshua Trentine March 6, 2013 at 9:58 pm



avatar Fred Hahn March 12, 2013 at 4:35 pm

It didn’t cause the pain Mark.


avatar mark March 15, 2013 at 4:04 pm

Thank you, doctor, for that thorough examination.


avatar Joshua Trentine March 15, 2013 at 4:07 pm



avatar Marc Noel March 5, 2013 at 7:58 pm


Great stuff. Is the third cam class the cam and follower?

You had better find a way to live forever, because the field of exercise will always need your expertise and precise comunication skills. I remember Greg Anderson imitating you when we’d speak. He’d sound as if he were reading from the SS manual. I start some sentences with “Realize”, and use the word “aproblematic” where applicable.

Thanks very much for this detail. Looking forward to the next installment.

Marc Noel


avatar Joshua Trentine March 6, 2013 at 9:53 pm




avatar enlite March 5, 2013 at 11:04 pm

This is a very interesting article indeed. Putting the issue of machine design aside which is important, i think the most important aspect of exercise with regard to safety is how the movement is performed. My personal experience over the last few years has definitely proved to me that a slow cadence vastly minimizes joint stress, while maximizing muscle contractions!


avatar Joshua Trentine March 6, 2013 at 9:53 pm

When arguments about exercise equipment design and protocol are debated, the big and invisible elephant in the room is the speed of motion. The elephant resides in a spectrum in which we are naturally blind. Like a blind person, we must all—apparently—be led to the elephant and made to feel its presence and repeatedly warned to stay out its way.


avatar Trace Johnston March 8, 2013 at 2:42 pm

Regarding the “invisible elephant.” Yes! It’s invisible to the general public, invisible to personal trainers, invisible to most researchers. More amazing is that those who see it are also invisible to the majority who clealy demonstrate a blind spot in their field of vision. Is this another dimension we’re talking about or is the world going through a paradigm shift?


avatar David Lee March 5, 2013 at 11:04 pm

Hey Ken

The entire post was a good read, I especially liked the last part. I am in the middle of going through your text. I think this should be required reading in every physio school. I read the second edition to the SS manual awhile back, and I didn’t really get it. Reading your Ren exe text….and something just clicked…your words seem so clear to me now. It’s fantastic.



avatar Joshua Trentine March 6, 2013 at 9:57 pm


I’m glad its starting to click….none of this stuff can be absorbed without multiple reads.



avatar John Parr March 6, 2013 at 12:35 am

Ken, thank you for such a thorough explanation of the equipment that I have spent the last 30 years using to train legs on. This is a subject that is near and dear to me since my legs used to be my best body part. In my 20’s and 30’s I had really strong and well developed legs and calves. I thought I was training them very intensely and safely, using the best equipment. At the age of 40, both of my knees were crippled with pain and swelling, I could barely walk at times. My legs quickly atrophied. Surgeries and therapy failed to improve them, doctors told me I would be looking at replacements in the future, I was too young to be a candidate they said. I started using your 10/10 protocol in 2009. As a result, I have almost made it back to where I was before having knee issues.

I wish I had this information years ago. Now, that the new RenEx line has been developed, I know I will be safely improving even more in the near future.


avatar Joshua Trentine March 6, 2013 at 9:56 pm


I have a similar story…I’m seeing big improvements in my knees in my 40’s…the RenEx Leg Ext is making a huge difference for me


avatar Denis Rogers March 6, 2013 at 6:17 am

Great article. I have heard it said that timing is everything. I just paid for a Medx Leg Extension and Leg Curl. Had I read this article first I probably would not have.


avatar Joshua Trentine March 6, 2013 at 9:54 pm

thanks Denis

We’re never more than an email away….


avatar Dan R March 6, 2013 at 7:44 am

What’s the best knee angle for static contraction?


avatar Joshua Trentine March 6, 2013 at 9:50 pm

Somewhere in midrange at a pain-free angle.


avatar John Tatore March 6, 2013 at 2:56 pm

“lubrication procedure performed in a knee extension machine”

How is this protocol done exactly?


avatar Joshua Trentine March 6, 2013 at 7:19 pm


We would like to save this info as part of the RenEx certification.



avatar Craig March 6, 2013 at 8:59 pm

The earlier parts of this series left me with the impression that shear stress in the knee exists in a leg extension exercise, but is overrated as a risk to knee health. Then this part indicates that you do want to go to full extension, but only if you move slowly and have the load roll off by virtue of a good cam design. What I’m not clear about is why are these precautions advised? Is it because of shear stress, or something else? What bad happens if the load is too high at full extension.


avatar Joshua Trentine March 6, 2013 at 9:18 pm
avatar Marc Noel March 7, 2013 at 12:19 am


While the following is not all there is to say about it, my thoughts are…

Assume the finished/most-contracted position in leg extension has the knee fully straight, and bodily attitude places the entire leg horizontal. In this position, the quads have to maximally support the weight of the lower leg, which does add some resistance to the total load (albeit a smaller-and-smaller percentage the stronger the person is). This assumes no body-torque cancellation of the lower leg. This means less external resistance can be supported than if the limb didn’t have to be supported, so less force from an external source. Also, look for a length/tension curve for human skeletal muscle on-line. It will show that strength decreases dramatically in the finished position. If we keep our speed adequately slow, momentum generation and contribution will be minimized, so lesser force will be imposed on the limb in that position. If the speed is adequately slow, but the resistance curve’s magnitude too high in that position, you just wouldn’t be able to move into it. You could if you threw it, or sped up, which is what sometimes happens when trying to use SuperSlow movement speed on non-SuperSlow equipment.

The foregoing reminds me of when someone says they lifted something too heavy. You can’t lift something that’s too heavy, because it’s too heavy. What they mean is too heavy to lift properly and safely. If you do it slowly enough, you won’t get hurt. You just won’t be able to finish the movement. If you speed, or, more-specifically, yank/heave, the force will be higher, and, possibly, high enough to injure.


avatar Joshua Trentine March 7, 2013 at 11:18 am




avatar Denis Rogers March 7, 2013 at 7:15 pm

“I assert all this with the understanding that I demand a 10/10 protocol. Without such speed control, most of these comparisons, if not all, are moot. I declare that this protocol speed is the most fundamental aspect of all of biomechanics and without its adherence a conversation about much else is pointless.”

How true that is and how long it has taken me to get that – amazing.


avatar Joshua Trentine March 7, 2013 at 7:22 pm

all the noise out there gets distracting sometimes….


avatar Fred Hahn March 7, 2013 at 9:52 pm

Where is your evidence?


avatar Joshua Trentine March 8, 2013 at 1:56 pm


We have learned what we claim through personal experience and through the experience of our thousands of sessions with clients. Further, the claims made in this blog are consistent with general knowledge and other evidence including basic physics and anatomy.

Any claim that we have made made in the discourse of this article provides a premise which logically justifies the conclusions presented. Such can be verified through of a trial on RenEx equipment in direct comparison to other equipment by anyone at any time thus neutralizing any cognitive bias in our claims.

The RenEx Team


avatar Fred Hahn March 8, 2013 at 3:00 pm

Well, after all these years you’d think you’d have performed some controlled research on the subject to support your opinions especially if you want people to take your claims seriously.

“I declare that this protocol speed (10/10) is the most fundamental aspect of all of biomechanics and without its adherence a conversation about much else is pointless.”

What – An 8/8 count is irresponsible and unworthy of discussion? The above statement is ridiculous. And why not 12/12 then? The basic concept we can all understand. But the absolute pronouncements you make (like the above) are without merit.

In any event, if a cam or cam effect is correct, the resistance curve will not be felt. What you will experience is a flat, unchanging load from start to finish. This is NOT the case with the SS leg extension machines I have used in the past.

The fact of the matter is, at full flexion the knee cap is indeed pressed into and in a sense crushed against the tibia and femur until you get to about 70 degrees of extension. This is plainly evident in clients who have arthritic issues since you can audibly hear the knee cap/bones rubbing against one another causing a creaking sound like a door that needs oil. But once past 70 degrees, this subsides since patellar tension reduces.

Bill DeSimone has it right. You guys (for the most part) don’t.

avatar Joshua Trentine March 9, 2013 at 12:12 am


You are welcome to your opinion.

We are curious why you worry so much about our approach, our claims and our protocol?


avatar Joshua Trentine March 9, 2013 at 12:15 am

BTW….both 8/8 and 12/12 are thoroughly covered in The Renaissance of Exercise technical manual.

avatar Joshua Trentine March 9, 2013 at 12:44 am


With regard to your comment that:

“Bill DeSimone has it right. You guys (for the most part) don’t.”-F.H.

I have two questions:

1)What don’t we have right? the word “it” doesn’t say anything.

2) Did you know that Bill DeSimone is currently endorsing the X-Force leg extension?…the most egregious offender of the exercise (with the net cam effect of 1:1.1).

So what is it that he has “right”?


avatar Fred Hahn March 9, 2013 at 9:28 am

Your group serves to make the world of HIT resistance training seem like a joke – just like it was in the SS days. You do the industry a disservice in many ways.

avatar Joshua Trentine March 9, 2013 at 12:48 am

To anyone who might disagree with this brilliant knee series Ken has written, we will be looking forward to your written thesis on the subject.



avatar Marc Noel March 10, 2013 at 1:22 am

Great response, Josh.

Where would we be if no one had standardized the inch, or the second? Speed is distance divided by time. Without those standardizations, it would be impossible to accurately and precisely measure speed (as an example). For those who’ve read the SS Technical Manuals (various editions), you will know that Ken had commented about different rep speeds, and even commented that anywhere between 8 and 12 seconds was acceptable, but we were aiming for 10. In my opinion, I think it should be EITHER 10 seconds or else as slow as the person can go without stopping, whichever is possible. Letting a trainee dictate their speed with a latitude from 8 to 12 is asking for trouble, primarily because they might start off slower, then speed up as they tire. A 12-second rep is 50% longer than an 8, and trying to count reps using various speeds is results in meaningless comparisons. Additionally, switching to the stopwatch won’t help, because of the differences in positive and negative strength. As I have said before, advising a subject to milk it for time is incorrect. If they are travelling at the correct speed, don’t encourage them to slow down. Undesirable variables end up getting thrown into the mix. In order to maximize accuracy and precision in performance and record-keeping, we must standardize rep speed, which Ken has done. He commented about 8 through 12, too, but 10 was a good compromise. Six seconds induced excessive momentum, and 15 or greater introduced segmentation. Once standardized, then we can proceed from there. Just like in drag racing: they set the track distance at 1,320 feet (1/4 mile), then everyone worked on maximizing their performance in that distance.

It is puzzling that some of those who are contrary should already know that Ken investigated faster and slower speeds, and used that information to arrive at 10 seconds.


avatar Joshua Trentine March 10, 2013 at 3:35 am


What’s even more puzzling is that the one that continues to nag with no position. Happens to be the same person that plagiarized Ken’s work and continues to recommend a fixed rep speed yet turns around only to argue with us….never a point , never a position…

…guilty conscious maybe? maybe its hard to be convinced when the thing you promote is just watered down junk that was borrowed/stolen from someone else.



avatar Joshua Trentine March 10, 2013 at 3:58 am


The work of RenEx and the many years that Ken put into developing SuperSlow is a joke?

How many years have you spent attempting to replicate this joke? poorly replicate i must add…

Question (of course I’ll never see an answer): What is not a joke? Who is working to advance exercise science???

If our work were a joke it would be very easy to write a rebuttal…we do it all of the time…I’m sure legitimate experts like yourself and DeSimmone should easily be able to rebut our work…do it…do it the the name of XForce! (the worlds best delivery system for soft serve resistance.)

You water down SuperSlow…lol…call it SlowBurn and that is to be respected?

It looks rather simple to me, you’re on the outside looking in and you can’t exactly figure how to steal any of this.

Besides having no position and no argument you are a walking contradiction….frequently contradicting your knock off book which you clearly don’t even believe in.


ps; Do us all a favor, put your Leg Extension video back up…it is a great contribution, I really like to show it to my trainers so they can see an example of everything a subject should NEVER do….when teaching I’ve never been able to perform all of the discrepancies simultaneously, you on the other hand are quite good at it.


avatar Joshua Trentine March 10, 2013 at 4:12 am


I must remind you that this thread is for comments on

Exercise for the Human Knee
Part III

by Ken Hutchins



avatar Steven Turner March 10, 2013 at 6:32 am

Hi Josh,

A great article on exercise for the human knee I can appreciate all the work that must have gone into putting this series together on exercise for the human knee.

I will admit that a lot of the information at first I don’t understand this doesn’t bother me because I know that you will explain it to me. Once I have re-read the article a few times and try and understand some of the physics I will get back to you to ask relevant questions. I don’t want to waste your time asking dumb questions that have little bearing on the article.


avatar Joshua Trentine March 10, 2013 at 3:58 pm


This all requires much repetition and often won’t seem all glued together unless you have the experiences to match the info.

We’re here to answer any and all questions you might have.



avatar Matt Spriggs March 10, 2013 at 10:32 am


Discussing speed is germane to this discussion since Ken stated that without 10/10 speed control other comparisons are moot. Perhaps this is correct – I am finding myself using a far slower tempo then I previously thought – more like 10/10 vs 5/5 I had been recommending. You berate Fred’s videos yet I’ve seen you perform exercises that did not resemble 10/10. Marc Noel has a really great site that demonstrates a SuperSlow workout. Not a single repetition is performed in 10/10 – look and see. The average is 6/6. Does this induce momentum? Either you guys don’t believe in what you are saying or you haven’t paid close attention to your own videos – what other explanation could there be? Lastly, following Fred’s “watered down version” as you pejoratively described I am making far better gains keeping my TUL ‘s shorter – closer to Fred’s recommendations as opposed to longer TUL – upwards of 4 minutes. My dissent is meant to offer a differing opinion, which I hope you welcome given the level of obsequiousness I see from many who comment on this site.



avatar Joshua Trentine March 10, 2013 at 3:55 pm


Go back and check reference:

This is right out of the SuperSlow techincal manual :

“We desire momentary muscular failure to occur within an ideal range of 40-70 seconds. This ideal range is often adjusted upward for the novice (4-8 repetitions or 80-160 seconds), but for the sake of this discussion assume the lower and upper guide times to be 40 and 70 seconds and the lower and upper guide numbers to be 2 and 5 repetitions.”-K.H.-

All of our guides are also in the RenEx manual…you guys should really read this stuff before repeating details we have never recommended.

From Appendix: B Super Slow Protocol Second Edition 1989. First question under the Question and Answer section:

Question: Doesn’t Super Slow training require more time to perform than the conventional lift-in-two-seconds-lower-in-four-seconds approach?

Answer: No. Super Slow requires the same time alloted to the set and the complete workout as the conventional method. The common repetition scheme of 8-12 repetitions for the standard protocol represents a window of time to achieve momentary muscular failure in approximately 70 seconds. This is the time frame we strive for in the Super Slow application.

Ken has never recommended 4min T.U.L.s for general populations with the exception of teaching or rehab…He has always made his recommendations clear yet the old guard will take and bend or pull out of context in an attempt to discredit.

I welcome a critique of ANY video I have put out…just remember-to a great extent equipment dictates protocol.

I will let Marc Noel speak to his own videos and the equipment he is using in them.

My positions stands:
The guidelines that have arisen were do to equipment… Much has been ironed out with RenEx. It just so happens that if the equipment is correct and instruction is spot on, something around 10/10 is the resultant rate of speed. I rarely ever tell a subject to move slowly to get this effect.



avatar Matt Spriggs March 10, 2013 at 4:58 pm


1) If you reference the second edition SuperSlow manual – kindly note that the suggested protocol was 10/5. 10/10 was refuted even if low friction equipment was available. 10/5 was described as “The Ideal Protocol”

2) If you now recommend 10/10, 2-4 reps would be the maximum possible in the time frame you describe. Are you saying you try to get people to reach failure within 70 seconds? Ken has never recommended 4 min TUL’s?? Why in “What is SuperSlow” that appears in the articles section of this website does he mention 1-4 minutes in the intensity section? It gives the impression that a set lasting up to 4 minutes is acceptable – especially if Ken refers to it as high intensity. Marc’s site lists a rep range of 4-8 and maximum of 12. This would result in sets that could last as long as 4 minutes and I assume he is aligned with Ken and SuperSlow philosophy.

3) You have excellent form – no question. It’s not 10/10 in some cases and this one really gets me – If the duo-squat and other unilateral exercises are potentially hazardous (I now know that they are after being seriously injured on the duo-press) why did you demonstrate this exercise as heavily as you could? Why did you use such a ballistic tempo? Are you immune from it’s deleterious effects or has the position changed on unilateral loading? You deadlifted an enormous amount of weight – what was the purpose of this? It in no way demonstrates the superiority of your equipment or the efficacy of your methods. You are strong.

4) I’m not posting on here to insult you or RenEx – I’ve learned a considerable amount from this site and Ken’s contributions to slow motion exercise are enormous indeed. I really like Marc Noel’s site and am not trying to say anything other than the obvious – those videos show subjects moving at speeds that aren’t consistent with the protocol.



avatar Joshua Trentine March 10, 2013 at 6:10 pm


Re #1: Yes, ideal for bad equipment, add 5 seconds to every rep and you still come out no where near 4 minutes….it clearly says; “the lower and upper guide numbers to be 2 and 5 repetitions”-K.H.-

Further refinements have been made in The Renaissance of Exercise technical manual in light of developments with RenEx equipment….that being said Ken made these recommendations long before Fred was an instructor.

Re #2: I can’t speak for Marc’s site, our recommendations are made clear in the manuals, furthermore I have observed many workouts supervised by Ken Hutchins and he has trained me many times and I’ve never witnessed a set even over 3min. Although I have personally done many initial consults where I had the subject on the Leg Press for 4 minutes…or more.

There is a HUGE difference between the learning stages and the actual workouts.

Re #3: I’m surprised you are even asking this…. In each case those demonstrations were done for the purpose of a corresponding article and this is CLEARLY explained in each article and for each video. I’ve said it a million times…”To a great extent equipment dictates protocol” -J.T.-

I’m happy to defend each video one by one, I find it redundant though…in each case my behavior is consistent or better than the manufacturer’s recommendations and I challenge you to show me one video of any of us using SuperSlow Systems or RenEx equipment where you can find ANY discrepancies.

Yes, I’m very strong and I wasn’t anywhere near as strong before I started using Ken’s stuff in the later part of the 90’s….You can take that for what ever its worth. I’ve said this many times- 42 year old Josh crushes 20’s and 30’s Josh….I’m not sure what else to blame this on….and i can better all of those old demonstrations today.

#4: I’ll check out Marc’s site, I have seen his videos in the past…he might be the best I’ve seen at making the most out of what he has. I’m fascinated by his mods.

Check the equipment in the videos and get back to me. ..Stock Nautilus and Tim Ryan modified MedX…

Much has been ironed out with RenEx…..

I log all of my workout in great detail….the fastest i’ve seen over the last year is a 7 second positive and if that occurs it occurs early in the set.



avatar Matt Spriggs March 10, 2013 at 6:28 pm

SuperSlow Manual Chapter 30
General Guidelines for Strength Conditioning

Guide Numbers 4-8 up to 10 even 11 or 12 if you predict a failure – whatever that means. This could still make up 3 minutes or longer and in most cases too long. Even if the set is ended at 10 reps it’s close to 3 minutes. Reread that section of chapter 30 and show me where I’m mistaken.

Why not 10/10 for bodyweight exercises back then? Did they have too much friction? It took RenEx to iron this out??

If you did a 7 second positive, is this consistent with your protocol?


avatar Bradley warlow March 10, 2013 at 10:55 am

Marc- I really like your comment in regards to standarizing rep speed.I also believe as well as this that it is important to standardize technique of performing the exercise. The attempt to keep these two variables intact during the performance enhances inroading and reduces the chances of respite.


avatar Joshua Trentine March 10, 2013 at 4:01 pm


Agreed… furthermore I see no other way to lay the ground work to train a subject…if the expectations are not clear how can you expect to control a subject’s behavior? What are you really doing for them?



avatar Joshua Trentine March 10, 2013 at 4:08 pm

read the Slow Burn website and see “Exercise vs…. PLAY”——-> plagiarizing much???.

lol…i wonder were that comes from? maybe:
Fred said to take three seconds to move the first inch, then no faster than one inch per second for the remainder. Using his suggested ten seconds, that’s eight inches of ROM.

I wonder where that recommendation comes from?

Can you say..watered down?…stolen?…bastardized?….ruined?


avatar Marc Noel March 10, 2013 at 4:54 pm

In response to Matt Spriggs:

Thanks for your compliment. You’re right about the rep speeds. I didn’t take the video footage for my website initially. It was for those who wanted a record of themselves. I later used the footage. Advocating a particular speed is one thing; compliance is another. It appears to be that, no matter how much you nag, some people still go too fast. I even count for some people, or use a metronome, and they still go too fast. A few will actually admit it, and try to conform. I use a metronome for myself, and a few others that will actually conform. Whatcha gonna do?


avatar Matt Spriggs March 10, 2013 at 6:05 pm


Agreed. And I would like to add that you have a straight-forward approach to your site that is very professional in my view. Do you see the shortcomings and pitfalls of certain absolutes? I’m not saying don’t standardize – I think we should and Ken has pointed this out better than anyone to my knowledge, BUT does it stand to reason that the people in your videos were EXERCISING? Well, if Ken is consistent with his previous statements regarding repetitions and charting performance, most of those repetitions would not have been counted because they would have been deemed too fast and if that’s the case I believe it crosses the threshold into absurdity. Also, I think the subjects demonstrated very good form and I observed no noticeable momentum, heaving or cheating all with repetition speeds outside of the 8-12 second range.



avatar Joshua Trentine March 10, 2013 at 6:22 pm

No one is saying that there isn’t an exercise affect outside of 8 to 12sec…Nor are we saying you can’t exercise outside of that range, but we are making arguments why it might not be the best to do so and certainly why it’s not appropriate with our equipment.

We are simply saying that on the ideal equipment those repetitions outside of 8 to 12 cannot be considered for any sort of performance guide.

Those reps do not qualify to make in onto the chart or play into the equation when formulating the next workouts exercise Rx.


avatar db144 March 10, 2013 at 6:00 pm

Josh selling many machines? How’s the competitive bodybuilding career?

Both dreams are dead. What to do next….



avatar Joshua Trentine March 10, 2013 at 6:14 pm

Do you really think you want to challenge me?


avatar db144 March 11, 2013 at 7:19 am

I challenge you to post the John Hopkins study you’ve suppressed.



avatar Joshua Trentine March 11, 2013 at 12:11 pm

I’m that powerful huh? the university of Johns Hopkins spends 50k to do research and lil ole me can suppress the findings…you really think that’s how it works?

They just started their trials.


avatar db144 March 12, 2013 at 5:47 am

I’ll come back in another year and ask the question again. I’m sure you’ll have an excuse as to why it still hasn’t been posted.


avatar Joshua Trentine March 12, 2013 at 3:09 pm

Not very well thought out there man….

my only role is to build the equipment…i don’t run the study, i don’t advise, i don’t secure NIH grants, i do not have a position at the university, i don’t not find the the subjects or the instructors.

thank you for assuming i’m so powerful, but its not the case and thank you for continuing to follow the blog.

avatar Donnie Hunt March 10, 2013 at 8:04 pm

And just what are these “big bombers” carrying Ken?! Lol! Seriously though, another great excerpt!


avatar Marc Noel March 10, 2013 at 8:55 pm

I decided to fire everyone that goes too fast. I now have three clients. Anyone got a couch I can crash on?

I LIKE to adhere to 10/5 and 10/10. If nothing else, I then know I’m not just fooling myself when I APPEAR to improve, when all I’ve done is change/break form. Having said that, the two primary reasons for the slow speed are safety and efficiency. If people are progressing and not getting hurt, that’s the main thing.

I know it sounds egotistical/boastful/whatever, but it always gladdens my heart when someone has a higher workload than me, but can’t do it slowly. Every time I have to re-set their speed, the weight must be reduced.



avatar Marc Noel March 11, 2013 at 2:08 am


In the 2nd edition of the SuperSlow manual, Ken talked about 1 – 3 minutes to failure. It later became 1 – 4 in subsequent publications. Related to this is McGuff’s literature about Signature Time Under Load, which is where the muscle won’t go any longer, but will do the same time with a heavier weight. All I do is monitor to see if a subject stagnates, and increase the weight if they do. If one is improving, then their rep count or TUL must be okay. Using a longer time keeps the weight and force down, which reduces injury potential. It is harder to go longer than go up in weight, so, for those who want more effort, I suggest trying to go longer. I have experimented with shorter TULS/lower rep counts, and Signature TUL. I currently use the 4 – 8 rep scheme for everything except calves, where I cut off at 10 when people graduate to 300 lbs. I also incorporate the Squeeze technique. The higher rep count, along with the Squeeze, makes it harder, so we can keep the weight down as long as possible. I have a Kevlar conversion on my leg press (also used for calves), and there is a resistance-doubling pulley mechanism where one belt section breaks about every 18 months, so I try to minimize the stress.

I find heavier weights for less time to not be as productive as the reverse. It can also discourage people when it feels excessive right from the start. As Ken said, if the weight is so heavy that we frighten people, they bolt. If it’s so light that they don’t get any results, they bolt. Weights are relative, meaning it’s so heavy NOW that only four reps are possible, but, over time, the person improves to eight. We then give a weight increase and repeat the cycle. The weight always ends up being heavy ENOUGH, which is what matters.


avatar Fred Hahn March 11, 2013 at 9:21 am

Marc –

You said: “I find heavier weights for less time to not be as productive as the reverse. ”

You “believe” this? Could you be more specific? I find your statement interesting since you are literally the only person I have heard state this. Everyone else I have spoken to has said the exact opposite.

The interesting thing about longer TCF’s is this: You HAVE to make the weight lighter. Since part of the game so to speak is progressing the resistance, how are you actually measuring or guaranteeing progress for your clients?

FE: If you give a client 200# on the MedX CP and his TCF is 2:00, you could easily – and I mean easily – raise the weight to 400#. His TCF might be 0:50 or so but so what?

Instead, most SS/RenEx trainers – if form was – uber-perfect – (are you people still subtracting reps/time for form discrepancies?) would raise the weight ~2lbs. or so. But the client is already fully capable of using 400#. Q: D0 you think you are building muscle (the REAL goal) by giving the client half or less of what his muscles are already capable of lifting?

If you do, you are delusional.

If you CAN move the load you are currently using in a given exercise fast – the load is too light to build muscle – WAY too light. You might stimulate some growth in a rank beginner, but you’re doing nothing for the majority of your clients.

Muscles move weights, not momentum. Only when lifting light weights (for the individual) can you generate enough momentum to unload the muscles.

Try doing Slow Burn for 60 days and then tell me you don’t see the difference.


avatar Donnie Hunt March 11, 2013 at 8:43 pm

Hey Fred,

At what point in a set do you feel that the weight should be so heavy that you can’t move the weight/movement arm fast?


avatar Fred Hahn March 11, 2013 at 10:10 pm

From the first rep.


avatar Joshua Trentine March 11, 2013 at 10:12 pm

This tells it all…

avatar Fred Hahn March 11, 2013 at 10:43 pm

It sure does Josh, it sure does.

avatar Donnie Hunt March 12, 2013 at 5:21 pm

@ Fred,

If memory serves me correctly, you”ve made your best mass gains once you started using loads such as this? Just to be clear, I’m just curious about what you have found to work best for you and your clients.

avatar Joshua Trentine March 13, 2013 at 6:58 pm

This is a response i copied from the BBS site written by Joe A….it fits perfect here.

I don’t mean to impose, so you can take or leave what I’m about to type.

I think your process can be improved and it would be more efficient and profitable in the long run. I’ve done exactly what you describe and it is self-defeating to an extent.

The biggest eye-opener for me in this regard was experiencing TSC with feedback. While my experience with it is limited and I won’t attempt to extrapolate and assume anything…it showed me how deficient my instruction was toward things that really matter. It gave me a preview as to how efficient it could be as a learning tool and gave me ideas of what I needed to do with clients to move them from point A to point B.

We tend to focus on form, body positioning, breathing, rep speed…but we do this b/c (whether we even realize it) we are placing the exercise itself as the key to experience/effect. We are trying to get the client to experience the workout before they acquire the skill or ability to actually perform it. In effect, we attempt to impose the stimulus on them…and it won’t work…it will impede their ability to learn (b/c they are forced to unlearn).

We must avoid allowing them to develop the mindset that the exercise (form, ROM, rep cycle, etc) is the point, that it is paramount to the experience. Rather, we must cultivate an experience that places them as the central governor of the entire process…that their intent/behavior drives the process (regardless of how it is physically expressed). They need to see how they affect the stimulus…not how to conform to the movement. Does that make sense?

From a business standpoint, I understand the urgency to get them feeling like they are exercising asap (perceived value); however, if you want to keep them forever, you need to engage them diferently. They need one thing to learn and focus on, and repeat (often) until it ‘clicks’. You are not a rep counter or a live metronome, you are an instructor. You instruct them in how to access their physiology toward the desired stimulus. Do that. Don’t try to teach them the mechanics of exercises and load them up and wait for them to work hard before you show them a ‘better path’. You may put them on a LP only, four days in a row to foster their connection to the real objective. This experience builds the foundation for inclusion of other applications (additional exercises) of that objective. At some point, they will actually have the ability to exercise themselves and can be moved to an appropriate dose (1/wk, 2/wk for x amount of exercises, etc).

Let’s say you charge x amount for a package of 10 sessions. Collect it, but don’t count that learning process against their sessions. Consider giving them that learning phase ‘free’ and the ongoing value of their experience will be higher.

Rather than having frustrated clients who are still ‘unlearning’ by the 10th session, you have engaged clients who are developing proficiency and can’t fathom exercising in another manner.

Sorry about the fagueness…some things can’t be worked out in 5 paragraphs. However, I noticed a significant change when I adjusted my approach with new clients. Like I said, not trying to offend; simply ignore if this isn’t helpful…” -JOE.A-


avatar Fred Hahn March 11, 2013 at 12:26 pm

“There was no difference between the CR and the VR groups at any angle and the magnitude of strength gains at any angle were similar for both groups.”

So why not do a simple study like this and see if your RenEx cams make a hill of beans of a difference in knee extension.


avatar Joshua Trentine March 11, 2013 at 4:16 pm

The purpose of the cam isn’t just to help promote strength gains but to facilitate safety throughout the entirety of the ROM and to ensure continuous effective muscular loading. The cam provides not only for the variations in capacity within the strength curve of the subject but also (and perhaps more importantly) it is instrumental in accommodating the exponential decreases in the subject’s energy as the set progresses. It is very important that you consider the dimension of time and total work in strength exercise rather than just the nature of strength within one single repetition. We are not robots with infinite energy. We instantly begin to tire the moment we begin any strength exercise. The cam must accommodate not only the immediate strength curve of the muscles but also the aggregate of all the reps to be performed: the entire set. Since we cannot have a different cam for every rep, we choose to work with a cam that is biased toward the latter half of fatigue in a set. In this way, the subject must volitionally and somewhat artificially control his performance at the start of a set, as the earliest reps constitute the “warmup” effect as well as the initial nervous communication with the structures. Then, as the set becomes more difficult, a more generous effort can be issued as the cam and muscles have finally caught up with each other. This can take place a few reps into a set, say for a beginner or delicate client, or literally by the end of the first repetition cycle. In an advanced subject’s 4-rep set, the cam has some value on rep 1 but it becomes critical at rep 4. It’s greatest effect is when the subject has just completed what will be the final rep.

A study would be most welcome but in the end, our primary concern is to build a machine that feels better than anything else we have tried. To that end, we are extremely happy with our design.


avatar Donnie Hunt March 11, 2013 at 8:51 pm

Hey Joshua,

I figured that the Renex cams must be designed in such a way or the same thing would happen during dynamic contractions that would happen during a static contraction with an external load.

Do you have any thoughts, yay or nay, with working in zones or partial reps when using free weights or machines that don’t properly vary the resistance? Reading some recent stuff by Brian Johnston got me thinking alot about this.


avatar Donnie Hunt March 15, 2013 at 10:28 pm

I’ve been trying to wrap my brain around, “Then, as the set becomes more difficult, a more generous effort can be issued as the cam and muscles have finally caught up with each other. This can take place a few reps into a set, say for a beginner or delicate client, or literally by THE END OF THE FIRST REPETITION CYCLE.” How does the subject then make make it to rep four?


avatar Joshua Trentine March 11, 2013 at 12:46 pm

Response to Matt Spriggs:


I have heard your comment about my supposed emphasis on the 10/5 protocol in the second edition of the SuperSlow Technical Manual hundreds of times. Each time I hear this I tell the reader to go back and reread the material. As Josh has already explained, 10/5 was a compromise for bad equipment, and I clearly state that in that edition.

Also note the context of that writing. It was written in 1992 when we had very few pieces of low-friction equipment available. I was making a few retrofits to lower the friction and correct the cams on some of the older Nautilus, but my re-engineered Nautilus and my SuperSlow Systems equipment was not available until the late 1990s and early 2000s. 10/10 for some exercises had to wait for these improvements, but I clearly intended that as the ideal.

Your comment about the TUL range deserves explanation. Note that the piece you reference—“What is SuperSlow?”—is a general-information piece aimed at the novice. In this brief synopsis I am explaining to the newbie that high-intensity exercise (in contrast to the expected and ubiquitous steady-state, ad-infinitum, low-intensity fare that people are doing) will be a set lasting somewhere between one and four minutes. I said this to cover all exigencies.

We have advanced subjects that begin to fail on the iPOPD at about 60 seconds.

We also have subjects who require an upper guide number of 10 repetitions on leg press and who—if at the outside speed of 12 seconds per excursion—will achieve 240 seconds. And these subjects sometimes fail at this upper extreme and still cannot begin the first repetition if they are increased 1% at the next workout.

And we have early-stage rehab subjects who maintain high TULs for a while until we are confident to meaningfully load them.

My temperament is to throw out the highs and lows until all those remaining possibilities are at less than two minutes TUL, but this is impractical, extreme, exclusionary, and dangerous for some subjects on some exercises.

All of the foregoing possibilities—and many more—are in that 1-4-minute range, but I did not in that general-information piece launch into the countless possibilities within that 1-4-minute range. That is not appropriate in that short piece, and is reserved for deeper and further reading and study beyond the introductory material.



avatar Joshua Trentine March 11, 2013 at 4:58 pm

To all,

I think we are very close to moving this to a pay site….i find this exciting as we can offer more to those interested.



avatar Marc Noel March 11, 2013 at 5:21 pm

But, but… I was just getting warmed up!


avatar gus diamantopoulos March 11, 2013 at 6:54 pm


Like many concepts, this approach to exercise is at once simple and utterly complex. The pendulum swings almost full circle because of how many disciplines this process and philosophy encompass. This may be difficult for you to understand but the seeming holes in what you have read are paved over with filler of praxis. You can describe and orange as round, and as juicy, having a skin and sections and pits. But no matter how hard you try, you cannot describe what the taste of an orange is. In every way that counts, a RenEx workout (on RenEx machines) is a big orange and we will never be able to describe its taste. There is but one way to experience it and that is to take a bite….



avatar Fred Hahn March 11, 2013 at 10:44 pm

Simple AND utterly complex. Gus…like stupid and smart?


avatar Steven Turner March 11, 2013 at 10:49 pm

Hi Josh,

I buy a car from you and you tell me that if I want to get 25 miles per gallon I have to drive the car at 50 miles per hour. I come back to you sometime later and tell you that I was only getting 10 miles per gallon you ask how and when were driving the car, for a moment think about all the variables that can occur when your driving. It would be near impossible to control all the variables when driving, but the constant is to get 25 miles per gallon is driving the car at 50 miles per hour. If you drive it at 70 miles per hour you are going to get a different outcome if you drive it at 20 miles per hour you are going to get a different outcome. From what I have read of you explanation on TUL it is hard to control all the variables. That is my take on this post.


avatar Joshua Trentine March 11, 2013 at 10:58 pm

Hi Steven,

T.U.L is not a variable to be controlled….it’s a side effect….resultant from certain behaviors.

We no longer even chart TUL anymore.



avatar Donnie Hunt March 11, 2013 at 11:28 pm

If I remember correctly, Al said something along these lines before? I think I get what you guys are saying. If I can keep my focus on keeping the muscles loaded with a reasonable amount of weight, without breaking form. I don’t count TUL or reps, because it seems to take my focus off of breathing (letting breathing happen), keeping the muscles loaded and maintaining form.

Looking at this stuff as the opposite of weightlifting (thanks Gus) and the opposite of conserving energy (Thanks Ethan, at idealexerise). Yes I know I’m off topic here lol, but just saying.


avatar Matt Spriggs March 11, 2013 at 11:02 pm


I purchased the manual and I eagerly await its arrival. I know you said this was closed, but subsequent comments have been posted and I would appreciate the courtesy of a response to Ken’s statement. This will be my final posting addressing this issue.

“We also have subjects who require an upper guide number of 10 repetitions on leg press and who—if at the outside speed of 12 seconds per excursion—will achieve 240 seconds. And these subjects sometimes fail at this upper extreme and still cannot begin the first repetition if they are increased 1% at the next workout.” KH

So you do have subjects perform this TUL who are beyond the beginner stage – this is in direct conflict with Josh’s previous statements.

Ken, you say you have heard my comment on your SUPPOSED emphasis on 10/5?

“Once friction was practically eliminated we adopted 10/5 both for its simplicity AND ITS IMPROVED LOADING DURING THE NEGATIVE PHASE.” and “I recommend the 10/5 protocol as THE IDEAL PROTOCOL to use with most subjects WITH LOW-FRICTION EQUIPMENT during most exercises.” KH

1-4 minutes – certainly upwards of 4 minutes can and do have a large aerobic aspect, but why use it? Look at a miler and compare their appearance to a sprinter. Rehab – why go much past 2 minutes for stroke survivors, MS, cardiac rehab, cancer or any other application? I do not believe such long durations are necessary or desirable.

Lastly, I have an affinity for your work and writings. I voice my dissent because I care – not to discredit you or your work. Your writings caused me to experience a paradigm shift and as a consequence redirected much of my focus and the direction in life. Thank you. As much as I admire you and your work – I wont be an “apple-polisher” or minion or as the saying goes “go along to get along.”



avatar Joshua Trentine March 11, 2013 at 11:57 pm

I’m fine running it, but I’m not sure how much more Ken is going to say.


avatar Bill S. March 12, 2013 at 1:00 am

Shocking how Josh is being treated by the HIT ‘old guard.’

You guys are exposed by your double standards and unprofessional behavior.

You never were interested in true progress, were you?


avatar Joshua Trentine March 12, 2013 at 1:26 am


It’s much easier for them to believe that the equipment and techniques they were using 15 years ago is good enough.

No one really wants to get their hands dirty trying to iron this stuff out…no one wants to find the hundreds of thousands of dollars needed to bring equipment design forward beyond that of the mid 80’s.

In my experience almost none of the community wants to do the work, yet they all want to be “the guy”….too much ego….and no real efforts towards making this as great as we all know it should be.

Now when someone wants to come along and do the work…they all freak out because they would like to believe they had something innovative and there is no way the old farts are going to spend anymore time or money improving.

It’s much easier for them to try to make us look bad rather than attempt to make themselves better.



avatar Marc Noel March 12, 2013 at 2:35 pm

Let’s start at the beginning. A man knows nothing about strength training, but he wants to get stronger. He can lift 100 lbs., but wants to lift 200. How does he do it? Let’s assume he arrives at the conclusion that if he can lift more weight, or the same weight longer, then that would constitute improvement. Lifting more weight obviously means one is stronger, and it doesn’t make sense that you could lift a certain weight more times, but your 1RM remained the same. So, there are only two things he can do: either just keep trying to lift heavier weight for the same time (from 1 rep to infinity), or try to go longer with a given weight. He can already lift 100, so he tries 105, but can’t move it. His only alternative is to try to lift less weight for a longer period. Now that he’s realized this, he MAY, over time, notice certain things, such as, if he uses a weight that is sufficiently heavy he can only lift it twice, he hurts himself, so he deduces that a lesser weight won’t hurt him, so he designates a minimum rep count. Now he experiments, then finds he can’t increase reps past a certain point, because of discomfort, waning concentration, or his body just refuses. So now what? The only way to try to improve is to increse the weight, which, most likely, will reduce rep count, and try to go longer again. This is what we do.

I know that the foregoing ignores statics, multiple sets, and Signature TUL (meaning: he MIGHT be able to lift more weight for the same time). Regarding these, statics have their place, but we are trying to improve multiple fitness aspects, not just strength, and my experience has shown less cardio involvement, and no addressing of flexibility, so statics are bumped. For multiple sets, doing proportionately more does not beget proportionately greater results, so multiple sets are bumped. Finally, it would be great if, once a Signature TUL was found, one could keep adding weight, and still get the same time. However, multiply it out, and even if you were able to go up 5% every weekly workout, after 28 weeks, you would have gotten 312% stronger, which I don’t think is realistic. Even a 2% increase would be a 186% increase in a year. Plus, 2% of 500 lbs. is 10. In comparison, there are some recommendations to add significantly more weight, percentage-wise. If done, either the person’s limit will be reached very quickly, or there is the assumption/expectation that he/she can keep taking larger increases. If the latter, then there should be subjects using 5, 000 lbs. My experience and observation has shown that people fluctuate in their capabilities. Today, they might lift it six times, but next time, only four. There are numerous, uncontrollable variables outside the workout environment that can affect performance. If people stagnate, I up the weight, and, sometimes, they can still do the same rep count. Most of the time, they can’t. If I followed the “heavier for fewer” philosophy, there would be times when some people couldn’t get started. That happens now, when some people did eight reps last time, get a new weight today, with a minimum of four, but they can’t get started. Imagine if they were expected to do the exact same time with more weight. I have asked people their opinions, and only one person in 14 years wanted more weight after four reps, so he would give up because of fatigue, not discomfort. Yet, that only worked for three workouts. At the fourth, he couldn’t even start. Anyway, I prefer to see a gross improvement, getting at least 7 reps with an attempt, before jacking up the weight. If nothing else, next time, even if they aren’t in perfect shape for a workout, they still get something out of it, vs. not being able to start.


avatar Fred Hahn March 12, 2013 at 4:44 pm

We increase people’s weight loads after 4 reps all the time with absolutely no problems.

Q:When a client can’t start the 1st rep what do you do? Just stand there? Talk about perfect form? Explain some baloney about over training and nervous system fatigue?

We help them start the set or, start them in the negative. Both work like charms.

And isn’t it obvious that it may take many bouts with the same weight load before an additional rep is achieved?

But my point remains – If your set times are longer than 90 seconds, progressing the resistance from that long set time is NOT progressing the resistance.


avatar db144 March 12, 2013 at 6:32 pm

LOL, Josh if you could think you wouldn’t be posting 30 year old SS information rewritten by you and Ken or for that matter standard text book information on anatomy and bio-mechanics. If either of you had a new idea I think the world would end.

Did you or did you not supply Hopkins with equipment and training free of charge? And even after that it took a year to secure a grant which will prove what? An injured person can be rehabilitated on RenEx equipment? Money well spent.



avatar Joshua Trentine March 12, 2013 at 8:21 pm

Perhaps I can’t think…. yet you continue to hang on my every word.

Johns Hopkins paid full retail price for their equipment.


avatar Dave March 16, 2013 at 5:52 pm

Josh, Who is teaching Johns Hopkins how to use RenEx equipment? If they dont know the RenEx way how could you consider any of thier findings valid in your mind since you say the machines and made for the protocol?


avatar Joshua Trentine March 18, 2013 at 2:19 am

We require certification money prior to sale of equipment, but we have had a few customers buy the certifications and not show for the testing… i never considered that this could happen.


avatar Marc Noel March 18, 2013 at 2:22 am

I guess that’s similar to clients who buy a six-month package, do four workouts, then disappear.

avatar Dave March 18, 2013 at 1:54 pm

Marc,Josh, its not similar to clients who buy a package and disappear. If the folks at Johns Hopkins are not certified then the study is not valid as to RenEx providing any advantage over other machines. If the folks at Johns Hopkins dont know how to use the machines properly you cant not say that RenEx has an advantage. I would think you would want it know that RenEx is the way to go. Like a feather in your cap so to speak.

avatar Marc Noel March 18, 2013 at 4:22 pm

I meant the attitude.

avatar db144 March 13, 2013 at 5:36 am

I stand corrected on the equipment provided to John Hopkins.



avatar John Parr March 13, 2013 at 11:55 pm

Well said! I have been frustrated with myself recently because I have not been able to get a few of my clients to behave the way I want them to. These particular clients are inconsistent. I think your post made me realize that I need to engage them differently. I need to teach them to learn to drive the process by their intent/behavior so they can feel how they affect the stimulus. Instead, I’ve been allowing them to think that the exercise itself(speed,breathing,etc.) is the key.
In summary, Thanks for reeling me back in.


avatar Anthony Diana March 16, 2013 at 10:45 pm

Ken…..Great series of articles! Amazingly detailed and explained. Your knowledge and expertise makes you the cutting edge of research and development in the exercise field! Keep writing these insightful articles and Best Wishes for the future!


avatar Joshua Trentine March 18, 2013 at 2:15 am


i’ll pass this on to Ken, thank you for the kind words.



avatar db144 March 17, 2013 at 3:03 pm


I love you.



avatar db144 March 19, 2013 at 6:22 pm

I am one of Josh’s groupies.



avatar db144 March 20, 2013 at 6:12 am

I want to play games!



avatar db144 March 20, 2013 at 7:46 am

I’ll be posting regularly so keep checking.



avatar Joshua Trentine March 20, 2013 at 12:12 pm

Thanks for stopping by….sorry, we will not be running any more comments that don’t relate to the thread.

The site will be moving to a pay forum sometime soon, this is a great opportunity for you to start over.

I’m looking forward to serious discussion and a windfall of innovation.



avatar db144 March 20, 2013 at 6:13 pm

Yes, please charge me, squeeze out the last penny.



avatar db144 March 20, 2013 at 6:28 pm

“For now, I merely give you the practical approach to sorting out when and when not to do either knee extension or leg press or both of these exercises. The rule is: If it hurts, don’t do it.”

Now no one else has to read the “masters” repetitive lesson.



avatar Joshua Trentine March 10, 2013 at 11:49 pm


The guides for each exercise are in the manual….none of them are anywhere near 4 minutes…

Bodyweight exercise is covered in the manual too…Ken clearly states that 10/5 was for the case when training on MACHINES that allow for a friction based respite…this was actually one of the first questions on the old SuperSlow exam…Ken did NOT recommend 10/5 for Body-squat, Push-up or Chin.

If you did a 7 second positive excursion that particular rep does not qualify towards consideration for load adjustments next workout.

In the manual you will see rep guides for each exercise listed as “min/max”…..”super min/max”….and “teaching”….the manual CLEARLY discusses who each range is for….its really a pretty simple thing to understand….if you read this and you think that the set is supposed to last for 4 minutes in an advanced subject’s workout then I probably can’t help you anymore

This thread is to discuss the knee articles….it’s not for me to answer the same questions over and over…ALL of this is covered in past threads and has been written about in the manuals.



avatar Matt Spriggs March 11, 2013 at 12:30 am


I am not trying to come across as irascible or argumentative, but your statements don’t seem fully consistent. Again, it strains credulity that 4 minute TUL’s are so strongly discouraged and were never recommended yet in the article “What is Superslow” it states the following by Ken verbatim “Brief activity causing a failure of the involved musculature within only 1-4 minutes is high-intensity.” AND “The resistance is either of efficient or of inefficient quality. If efficient, the muscles find little or no respite and fatigue within 1-4 minutes.” And he’s never recommended 4 minute TUL’s? What was he referring to and why? I’m sorry if answering these things frustrates you, but if you and your colleagues make such declarations “I declare that this protocol speed (10/10) is the most fundamental aspect of biomechanics and without its adherence a conversation about much else is pointless” defending these statements and your own seemingly lack of adherence at times seems to warrant a thorough explanation. In fairness, I do not posses the RenEx manual and will purchase it. I also admire the form and precision in your workouts.



avatar Joshua Trentine March 11, 2013 at 1:01 am


We will be looking forward to your critique of the RenEx manual.

You’ll find everything you need in there.



avatar Joshua Trentine March 11, 2013 at 12:16 pm

posting for Gus:

Dear Matt,

We always appreciate anyone who takes the time to actually read any of this material, so thanks for your interest. But please don’t strain too much to solve any seeming contradiction here. In fact, there is no conflict at all.

The recommendations that you have read about in the earlier material does not in any way interfere with our present suggestions. The technical manual goes hand in hand with our certification and study materials; these are materials that relate directly to how instructors conduct and administer sessions with actual clients in real world scenarios.

The longer load times/larger rep numbers have always been part of the protocol as part of the teaching portion of any exercise. These load times are also suitable for introducing new exercises to a subject who has experience and especially for improving performance in subject’s who are engaging in numerous discrepancies such as improper set commencement, firing out of the bottom out, and any other improprieties. The longer set is an uninterrupted event that permits the instructor to cover much ground simultaneous to the subject’s performance. In most cases, subjects don’t remain in the teaching times for more than a session or two.

Another possible reason for longer load times are debilitated subjects who require extra lead time to nervously communicate with their structures. If you’ve never worked with a stroke victim or other debilities, it will be difficult for you to understand the needs of these clients when compared to any conventional subject’s needs.

At the shorter end of the spectrum, the 1 minute or smaller rep numbers, we are obviously working with stronger, more advanced subjects. These are the kinds of subjects who are experienced and whose workouts are expertly performed with few discrepancies.

Most intermediate subjects perform at moderate load times and repetitions and this is dependent on the particular exercise, experience level, and routine.

This is obvious to anyone who would spend a half day or so in any facility where this practice is common.

Since you haven’t read the manual, we highly suggest that you acquire a copy and read thoroughly.



avatar Matt Spriggs March 11, 2013 at 4:44 pm


Thanks and I appreciate your civility. No strain felt – Josh and Ken’s statements don’t seem consistent. First, according to Josh he never recommended such long TUL’s, then they were only under certain circumstances. How far back do you wish to pedal? Look at what Marc Noel posted – he claims that subsequent literature recommend 1-4 minutes to failure. Is he mistaken as well? If this is the case, I recommend improving upon your communication and disseminating information that is more easily understood, digested and applied by those who claim adherence to your protocol. I will promptly purchase your manual and consult it carefully. I appreciate your work and contributions and I do not say this sardonically.
The nonsense in the fitness industry grows worse on a daily basis and I give a lot of thanks and credit to Ken for opening my eyes to much of this detritus, but you guys are becoming an isolated island unto yourselves – almost a form of esotericism. Maybe this is intended, but I do not believe this behooves you or the HIT community as a whole.



avatar Joshua Trentine March 11, 2013 at 4:56 pm


The context was discussing extended T’.U.L’s for general populations and muscle building purposes.

Rehab is another matter all together…

I hope we have answered your questions, this thread to closed to anymore posts on rep range guides.



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