# What is the relationship between size and strength? **URL:** \ **Category:** Factual Questions\ **Created:** [March 11, 2005, 5:31pm UTC](https://boards.straightdope.com/t/what-is-the-relationship-between-size-and-strength/294048 "2005-03-11T17:31:46Z")\ **Posts on this page:** 14\ **Page:** 1
**Author:** ![jebert](https://avatars.discourse-cdn.com/v4/letter/j/ec9cab/32.png) [@jebert](https://boards.straightdope.com/u/jebert)\ **Post date:** [March 11, 2005, 5:31pm UTC](https://boards.straightdope.com/t/what-is-the-relationship-between-size-and-strength/294048/1 "2005-03-11T17:31:46Z")
Competitive weightlifters are divided into classes according to weight. The bigger the competitor, the more he can lift. I would expect that there is some relation between size and strength such that, if I know the world record at one weight class, I should be able to predict the record at other weight classes. From scaling theory, the mass of an object increases as the cube of its linear dimension, whereas the strength of an object increases as the square of its linear dimension. So I would expect the strength of an object to increase as the 2/3 power of its mass. From this I would expect weightlifting records to increase as the 2/3 power of the weight class. Using data from here: [http://www.iwf.net/wrec/world.html](http://www.iwf.net/wrec/world.html) I did a regression on the various weight classes for snatch, clean and jerk, and total lift. The results for this set of numbers indicate that strength increases as the 0.544 power for the snatch, 0.575 for the clean and jerk, and .581 power for total lift. What accounts for the difference between the empirical results and what scaling would predict? ---
**Author:** ![Bambi\_Hassenpfeffer](https://avatars.discourse-cdn.com/v4/letter/b/bbe5ce/32.png) [@Bambi\_Hassenpfeffer](https://boards.straightdope.com/u/Bambi_Hassenpfeffer)\ **Post date:** [March 11, 2005, 6:13pm UTC](https://boards.straightdope.com/t/what-is-the-relationship-between-size-and-strength/294048/2 "2005-03-11T18:13:49Z")
Because humans don’t quite fit scaling theory? There are support systems in human beings that become larger as body size increases that have nothing to do with overall muscular strength. Bones may be larger, there is an increase in blood volume and the size of the cardiovascular system, and I’m sure other things I’m forgetting. Also, you also must realize that people are not necessarily directly comparable to each other in things such as strength relative to size. The leader in each weight class undoubtedly has a different level of stored fat and water when compared to the other leaders (which will affect weight but not strength), as well as differing lengths of bones and attachment points for muscles (which would affect strength, but not weight). I hope you can get what I’m trying to say here, and if not, that someone else will be along shortly to clarify. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [March 11, 2005, 6:29pm UTC](https://boards.straightdope.com/t/what-is-the-relationship-between-size-and-strength/294048/3 "2005-03-11T18:29:59Z")
I see two problems. First is the power-law assumption: Remember that a person has to lift his own weight as well. Suppose you were to try a model of strength = weight[sup]2/3[/sup] - k\*weight (with k some constant)… Would that fit better? The second problem, though, is that you’re dealing with the records, and records are always outliers. Suppose that the 205 pound man is able to lift much more than the model indicates: That might just mean that there’s only been one weightlifter since records were kept who was that freakishly strong, and that that one freakishly strong man just happened to weigh 205 pounds. I would expect much cleaner statistics from averages of some sort, or at least from something like the fifth-strongest man in each category. ---
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [March 11, 2005, 6:32pm UTC](https://boards.straightdope.com/t/what-is-the-relationship-between-size-and-strength/294048/4 "2005-03-11T18:32:31Z")
The correlation between a muscle’s cross-sectional area (which only correlates so well with its weight) is only about .67. That’s another complicating factor. ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [March 11, 2005, 6:35pm UTC](https://boards.straightdope.com/t/what-is-the-relationship-between-size-and-strength/294048/5 "2005-03-11T18:35:26Z")
It seems to me that the bigger you are the stronger but the weaker you are in proportion to your size. When I was in the Army I weighed about 140 lb. and could regularly do more chin-ups than guys who weighed 200. But they could lift a lot more than I could. ---
**Author:** ![barbitu8](https://avatars.discourse-cdn.com/v4/letter/b/839c29/32.png) [@barbitu8](https://boards.straightdope.com/u/barbitu8)\ **Post date:** [March 11, 2005, 8:08pm UTC](https://boards.straightdope.com/t/what-is-the-relationship-between-size-and-strength/294048/6 "2005-03-11T20:08:31Z")
Although there is an obvious correlation between size and strength, two other factors come into play: recruitment of additional motor units and increasing their rate of firing. Once an exciting stimulus reaches a threshold of intensity for that nerve fiber, it creates an action potential. Further increse in the intensity fails to increase the size of the deflection. Either the single fiber does not respond with a spike or it does so to its maximum ability. This is known as the “all-or-none law.” During a short interval following the passage of an action potential, no stimulus, no matter how strong, can initiate a new impulse. This is known as the “absolute refractory period.” For the next few milliseconds there is a relative refractory period, during which it is possible for a second action potential to be obtained. The refractory periods occur as a result of the temporary disruption of the sodium and potassium carrier mechanism caused by the first action potential. Any increase in strength must depend upon supplying nerve impulses of sufficient intensity to recruit the maximum number of motor units. However, another factor involves the rate at which individual motor units are contracting. If a muscle stimulus is followed by a second one before the first is over, the total tension porduced is increased. So, the scaling theory does not apply to human strength. Better training techniques many enable one to gain more strength without bigger muscles. Incidentally, muscular hypertrophy does not result because of new muscle fibers, but as the result of enhancing the contractile ability of muscle fibers. The nitrogen component (actomyosin) of the myofilament increases as a result of training. Myosin filament concentration increases with a reduction in the distance between myosin filaments, and fewer actin filaments in orbit round a myosin filament. In other words, there is an increase in the packing density of the interdigating filaments within a cell, plus a changing ratio of actin to myosin. Eventually a change in the cross section of muscle will occur if heavy-resistance exercises are carried out systematically. These alterations are reflections of ultrastructural changes. Similar changes occur in connective tissue. Ligaments respond by becoming stronger, and tendons and other components of connective tissue increase in thickness. ---
**Author:** ![Dubious\_Sacrifice](https://avatars.discourse-cdn.com/v4/letter/d/f08c70/32.png) [@Dubious\_Sacrifice](https://boards.straightdope.com/u/Dubious_Sacrifice)\ **Post date:** [March 11, 2005, 9:10pm UTC](https://boards.straightdope.com/t/what-is-the-relationship-between-size-and-strength/294048/7 "2005-03-11T21:10:54Z")
Not sure, but [Ron Bath](http://www.pullingjohn.com/players/ron_bath.php) routinely beats people younger and bigger than he his in Arm Wrestling. [Check him out](http://www.pullingjohn.com/players/ron_bath.php) ---
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [March 11, 2005, 9:18pm UTC](https://boards.straightdope.com/t/what-is-the-relationship-between-size-and-strength/294048/8 "2005-03-11T21:18:04Z")
At the top levels, arm wrestling has more to do with technique than raw strength. ---
**Author:** ![Dubious\_Sacrifice](https://avatars.discourse-cdn.com/v4/letter/d/f08c70/32.png) [@Dubious\_Sacrifice](https://boards.straightdope.com/u/Dubious_Sacrifice)\ **Post date:** [March 11, 2005, 9:36pm UTC](https://boards.straightdope.com/t/what-is-the-relationship-between-size-and-strength/294048/9 "2005-03-11T21:36:18Z")
> [@ultrafilter](#): > > At the top levels, arm wrestling has more to do with technique than raw strength. That’s true, but what about match-ups between guys who both have good technique? [Marcio Barboza vs. Ron Bath (Get A Grip 2005)](http://www.pullingjohn.com/matches/match.php?id=134&vid=mov) for example. Barboza is almost 20 years younger than Bath, and is much bigger, with larger muscles. Yet, they are dead even. By all accounts Barboza should be crushing Bath. And Bath does this routinely against top guys, with good technique, who are much bigger than he is. Don’t get me wrong, Bath is strong, very strong. He just doesn’t look it. ---
**Author:** ![Valgard](https://avatars.discourse-cdn.com/v4/letter/v/7feea3/32.png) [@Valgard](https://boards.straightdope.com/u/Valgard)\ **Post date:** [March 11, 2005, 10:36pm UTC](https://boards.straightdope.com/t/what-is-the-relationship-between-size-and-strength/294048/10 "2005-03-11T22:36:32Z")
> [@David Simmons](#): > > It seems to me that the bigger you are the stronger but the weaker you are in proportion to your size. > > When I was in the Army I weighed about 140 lb. and could regularly do more chin-ups than guys who weighed 200. But they could lift a lot more than I could. Not necessarily. For example, I used to work out with a friend who weighs about 300 pounds (I’m about 200 pounds). In proportion to his size he is still far stronger than I am (for example he could bench 50% over his body weight, I was never able to do that). ---
**Author:** ![Carnac\_the\_Magnificent](https://avatars.discourse-cdn.com/v4/letter/c/ccd318/32.png) [@Carnac\_the\_Magnificent](https://boards.straightdope.com/u/Carnac_the_Magnificent)\ **Post date:** [March 11, 2005, 10:59pm UTC](https://boards.straightdope.com/t/what-is-the-relationship-between-size-and-strength/294048/11 "2005-03-11T22:59:56Z")
> [@Valgard](#): > > Not necessarily. For example, I used to work out with a friend who weighs about 300 pounds (I’m about 200 pounds). In proportion to his size he is still far stronger than I am (for example he could bench 50% over his body weight, I was never able to do that). Generally, it’s true. I’ve seen ripped guys in gyms who can’t do 10 regulation chinups. Pathetic. One guy I saw the other day needed help doing them. I almost busted out laughing, but didn’t want him to throw me through the wall. ---
**Author:** ![Kent\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kent_clark/32/105_2.png) [@Kent\_Clark](https://boards.straightdope.com/u/Kent_Clark)\ **Post date:** [March 11, 2005, 11:01pm UTC](https://boards.straightdope.com/t/what-is-the-relationship-between-size-and-strength/294048/12 "2005-03-11T23:01:53Z")
Since my son is a competitive weightlifter, maybe I can shed some light. Your intitial premise is flawed. If it were accurate, any weightlifter in any class should lift the same as everyone else in the same class. Obviously, this doesn’t happen. If your premise were accurate, every single weightlifting competition should show an exact linear relationship between an average lift for one class vs. other classes. That doesn’t happen either. And, as your research showed you, it doesn’t hold true for record lifts, either. In addition to pure strength, there are factors such as overall physical condition, training, type of equipment used, state of mind, etc. And technique is important in weightlifting. When my son’s technique is right, he can easily lift 20 kg more than when he’s off. ---
**Author:** ![Cisco](https://avatars.discourse-cdn.com/v4/letter/c/ccd318/32.png) [@Cisco](https://boards.straightdope.com/u/Cisco)\ **Post date:** [March 13, 2005, 8:03am UTC](https://boards.straightdope.com/t/what-is-the-relationship-between-size-and-strength/294048/13 "2005-03-13T08:03:51Z")
> [@Dubious Sacrifice](#): > > [Marcio Barboza vs. Ron Bath (Get A Grip 2005)](http://www.pullingjohn.com/matches/match.php?id=134&vid=mov) I can’t even comprehend the force that’s being exerted on that guy’s arm, especially in the first round, before the foul. How do they prevent armbreaks, or are they common? ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [March 13, 2005, 8:22am UTC](https://boards.straightdope.com/t/what-is-the-relationship-between-size-and-strength/294048/14 "2005-03-13T08:22:53Z")
Another issue in (stand up) weightlifting as you scale up is that you need a certain amount of body weight to control and counter balance the weight you are handling.