What Can a Wrench Teach You About Strength Training?

Most of you have used a wrench before at some point in your lives. Did you know that wrench mechanics can actually teach you a lot about biomechanics? In the video below, I’ll show you the three ways in which you can increase torque production through a wrench, and then I’ll show you how hypertrophying the gluteus maximus will increase hip extension torque through all three mechanisms.

In the Biomechanics of the Squat & Deadlift Manual in my 2 x 4: Maximum Strength product, I go into further depth and show actual calculations using CAD drawings (thanks to my talented colleague Andrew Vigotsky).

Sammie Before-After

This is such a fundamental aspect of strength training and one that’s been overlooked. To this day, I’ve never seen any sports science expert mention how muscle hypertrophy improves torque through more than just increases in muscle volume/physiological cross sectional area. It also does through via increased force efficiency and increased muscle moment arm. In scouring classic manuals such as Supertraining and The Science & Practice of Strength Training, I was surprised to find that Siff, Verkoshansky, and Zatsiorsky never mentioned this.

Bottom line: hypertrophy is good for strength! A bigger muscle is a stronger muscle.

wrench torque


  • Todd says:

    Hi Bret,

    Great description thanks for sharing! I have definitely heard the idea that hypertrophy can improve torque through changing the angle of the muscle to the bone. I can’t remember where I learned this (maybe from Bill DeSimone?), but I happened to be thinking of this just the other day in the gym for some reason. Congrats on 2×4 BTW and best of luck with that.

  • Dunkman says:

    Geekiness people can actually use. Outstanding. Thanks.

  • Mark says:

    Great to see you can walk the ‘torque’ 🙂

  • Alex says:

    Geek error check:

    I hate to get all technical, and whatnot-

    The bubble say “SI Unit example”, but English units are shown.

    The engineer has spoken.

  • Melly Testa says:

    I watched the video (great glute drawing on white board), and I was once again assured that you are an awesome coach and that I am happy to be learning from you.

  • Smokewillow says:

    Bret, here’s video of Yohan Brake (co send of fastest 100m sprinter of all time) weight training.

  • Will Arias says:

    Hi Bret, spot on. It’s actually astonishing how such “S&C Bibles” (“Supertraining” or “Science & Practice of Strength training”) didn’t spend too much space to talk extensively about fundamental biomechanics of Strength. Zero entertaining analogies like the Wrench and the bolt, the crane and the stone and others that come to mind from the weight room and daily life itself. However, in the expanded edition (2009, pages 17-23) Verkhoshansky invested only a few of paragraphs of the 578 pages book to describe essential terminology associated with the torque/moment, the implications of the ‘moment of a force”, “moment of a couple” explains the differences between “forces of torque’ and “maximal strength”, etc. He kindly mentions papers leaded by Zatsiorsky (1964) Komi (1964) and McGill (1995) when describing the hyperbole Force-Velocity curve (Hill, 1953), though.

    In regards to Zatsiorky’s master piece, the 2nd Edition only mentions (when describing Accommodation Resistance and Accentuation Principles) an example in regards to some machines (nautilius style equipment), where resistance is applied with the “human strength curve” in mind. Nothing fancy, just describing how, in his words, “the resistance force or applied force is variable so that the load varies accordingly”.

    Finally, we don’t have to agree with EVERYTHING that our Strength and Conditioning leaders say. However, I reckon that one of the best pieces about Pulling Mechanics is featured in Rippetoe’s most recognized book, “Starting Strength”. As some of your readers might not be familiar with it, below is a link in regard to that fascinating topic, including the Wrench analogy and some others like the seesaw, the load-sided barbell, the garden rack and , obviously, the human hip, as “class 1 lever” or “a typical moment of a Couple” as described by Verkho in Supertraining. http://startingstrength.com/articles/pulling_mechanics_rippetoe.pdf
    Sorry for being such a pain in the neck with my long comments. Take care. Will

  • chris says:

    i was going to say “relax, guys”, even before reading will´s comment 🙂

    a) textbooks are not required to be entertaining, although they could benefit from good analogies.

    b) starting strength has pages full of those analogies. seems like that even for bret, a look into that would save lots of questions and work.

    c) of course its nice to have an additional piece that explains these mechanisms here on the blog, as people seem to forget about b) these days.

  • chris says:

    p.s.: it took me ten seconds to browse through “science and practice of strength training” to find pages about forces, torque with lots of graphs and human levers. see pages 40-44.

    • Bret says:

      Will and Chris, you didn’t listen to what I was saying in the video.

      I realize that discussions of torque have taken place and that the wrench analogy isn’t novel. What I was referring to in the video is the notion that muscle hypertrophy increases the moment arm. In all fairness, I didn’t really draw the muscle moment arm correctly in the video as I didn’t want to get too in depth and wanted to keep it simple. A muscle moment arm is the perpendicular distance from the joint center to the muscle’s line of pull. A muscle like the glutes is curvy, so its line of pull is difficult to figure out (it’s different for point on the curve, so you could have a tangential line at each point but really the muscle is wrapped). Anyway, if the muscle grows, it’s line of pull will be further out, thereby increasing the muscle’s leverage. I’ve never seen any sports science author discuss this concept. Not Siff, not Verkoshansky, not Zatsiorsky, not McGill, no DeSimone, not Rippetoe. Nobody.

      If I’m the first strength guy to figure this out, then I’m pretty proud of myself for it as I feel that it’s pretty important. I actually talked with professor Sylvia Blemker on Skype, who I believe to be the world’s leading expert on this topic. Here are some resources that illustrate this concept:


      • Will Arias says:

        Bret, Cool down, mate. Firstly, I LISTENED what you said in your video. Secondly, my comment was made as a humble contribution to highlight the difficulty to find PREVIOUS and RELIABLE evidence-based literature in regards to fundamental biomechanics of pulling Strength.
        Clearly, I didn’t elaborate my ideas sufficiently. All credit to you for your findings about the advantage of increasing muscle mass for the sake of enhancing leverage.
        Sadly, far from “icing on the cake”, my previous words obviously ofended you, which it reflexes your decision but not my intention. Thanks for the links, by the way. Take care. Will

  • chris says:

    bret: of course rippetoe describes the concept of hypertrophy and subsequent better moment arms in “starting strength”. at least twice, with drawn illustrations. once for the upper leg muscles in the squat and for the pectoralis for the bench press.

    • Bret says:

      Chris, really? If so, I’m impressed. What Starting Strength edition? Can you give me page numbers please? I want to check this out. Way to take the wind out of my sails haha.

  • chris says:

    youre sailing a great course anyway, bret. we were just born too late to discover everything 🙂 . maybe because of rippetoe, maybe bc of some other authors, this concept is not unknown to experienced lifters and probably not unknown to any sport scientist in biomechanics.

    starting strength, 3rd edition. chapter “bench press”, subchapter “chest”. two subsequent illustrations of a chest and thighs, respectively. explanation of the phenomenon in the accompanying text. maybe in other places as well, i just browsed for the paragraph i remembered.

    disagreements with a lot of mark rippetoes opinions notwithstanding, i dont get tired to recommend to everyone to study ss thoroughly before even thinking of asking or writing anything 😉 .

    • Bret says:

      Chris, I just bought SS 3rd edition. It’s incredible! Much better than the 1st and 2nd edition! Anyway, I did see that Rippetoe discusses the line of pull and efficiency, but not the increased moment arm. They’re two distinct features, both of which increase torque. Crazy, I thought I thought of all this stuff first, but it turns out that his 3rd edition is full of improved material, much like what I have in my new biomechanics of the squat & deadlift manual (his pictures are much better, but we use CAD). Anyway, very cool. In the first page of 2 x 4, I thanked a few people for imparting their knowledge onto me, and Mark was one of these people.

  • Duncan says:

    Lon Kilgore has also mentioned the advantages of improved leverage through hypertrophy. I think in the book’s Anatomy Without a Scalpel and Fit.

    • Bret says:

      Thanks Duncan. Does he mention improved line of pull, or increased moment arm? Again, they’re different. Lon and Mark were way ahead of their time.

      • chris says:

        imo lever arm length and angle of pull are so closely interrrelated i counted them both in when i saw rippetoe´s illustrations for the first time back then. but i dont wanna stunt your excitation and wont charge you any license fees either.
        well, a hip thruster would do the trick 😉 .
        keep up the good work and greetings from germany!

  • Keith Dow says:

    To put it in layman’s terms, torque = R * Force * sin(theta). Your contribution is to identify hypertrophy as as a factor increasing theta and therefore increasing the magnitude of the torque.

    • Bret says:

      Keith – that’s layman’s terms to you haha? You overestimate the layman’s understanding of mathematics. Okay, great discussion. I propose that hypertrophy increases R, Force, and theta in your equation. R is the moment arm, which increases via hypertrophy. Force increases via more contractile power via hypertrophy. Theta increases via improved angle of attack via hypertrophy. Therefore, with say 30% hypertrophy, you might get 50% greater torque due to the combined effects. This doesn’t quite match up with training studies, but nevertheless it makes for a good model and good theoretical discussions.

      • amc says:

        Bret, on a totally different note, angle of attack is also a term used in aeronautics.

      • Keith Dow says:

        Thanks for the reply Bret. I can see how hypertrophy increases torque via force and angle, but isn’t R just determined by the attach points of the tendons?

        Also I bought your book “Strong Curves”. I am adding some of the exercises to my routine. Thanks for writing it!

        Lastly, I read the article you recommended by Brad Schoenfeld. It is interesting that he recommends 6-12 reps. You might ask him about this article:


        1-5 Reps – Lead to a maximum increase in relative strength and myofibril recruitment.
        6-8 Reps – Produce the best medium between myofibril and sarcoplasmic hypertrophy.
        9-12 Reps – Increase sarcoplasmic hypertrophy at the maximum rate.
        >15 Reps – You move into the range of muscular endurance where hypertrophy gains slow.

        It seems like there are at least two mechanisms for hypertrophy. To hit both to the maximum it looks like you have to do a mix of 1-5 and 9-12 reps.

        Thanks for your time.

        • Bret says:

          Keith, no, it’s not. It’s the perpendicular distance from the joint center to the line of pull (which is hard to determine with curvy glute muscles, which is why modelers use a “wrapping” technique). Brad wouldn’t like the article you linked as it’s oversimplified. But I do agree (as does Brad) that lifters should employ a variety of rep ranges to maximize hypertrophy (1-5, 6-12, and 12-30). Many mistakenly believe that 30 reps is light/easy, but if you go to failure, it’s as brutal of a form of training as anything. We’re doing a study right now and people are puking from 30 rep sets to failure.

  • Bill DeSimone says:

    Hadn’t googled my own name in a while and this popped up.
    I mentioned the internal moment arm changing with hypertrophy in passing in ah, Moment Arm Exercise, ten years ago, but then things pulled me to a more joint-oriented approach in Congruent…
    Flattered to be mentioned in a group of “sports science authors”, but I’m not remotely in that group. I’m not an academic, nor a prolific writer. Actually, I’m kind of surprised to be on the radar here. I’m a trainer, with some experience and certifications, and when I come up with something that may be useful (usually a result of my own mistakes) I put it out in some format. But definitely not in the same class as the host here or the other names he mentioned.

    • Bret says:

      Hey Bill, I actually purchased your book years ago when I started getting interested in biomechanics and found it to be very useful. You were ahead of your time my friend. Nice job, and your humility is very rare in this field. Much respect, Bret

  • Bryce says:


    First, long time fan of your innovations. Keep up the good work.

    Question: If the muscle attachement is analagous to where your hand is on the wrench, how can making a bigger muscle increase R? Bigger biceps don’t move the muscle attachment distally on the radius, do they? Obviously, if my bicep inserted an extra inch down my radius, this would hugely increase my strength, since R would be increased. But no amount of hypertrophy can cause this to happen, can it?


    • Bret says:

      Bryce, see the articles I linked earlier in the comments section on how to calculate muscle moment arms. It’s the perpendicular distance from the joint center to the line of pull. You can alter the line of pull via larger muscle bellies. This is difficult to grasp at first, as we want to only consider the origins and insertions.

  • Bryce says:

    Bret, I thought about it some more, and while the effect of a thicker belly would have to be very small in comparison to the effect of a moved insertion, I can now see how you are correct.

    Perhaps the great untapped market in plastic surgery/orthopedics is the elective shifting of muscle insertions?

    • Bret says:

      Bryce, I’ve heard stories that the old Soviet team experimented with this method, but found that it wasn’t fruitful – maybe due to issues with coordination. Could be an old wive’s tail, or maybe it’s legit. I wouldn’t doubt it haha!

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