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Background:

I was working out with some friends today and during one of the exercises (jump squats) I jokingly said to my buddy (who is 5'4" with a normal proportioned frame, I have a lean build) when he was cheating on the exercise a bit, "Hey man, these are harder for me because I'm taller and weigh more, so no excuses!" and laughed. I said it in jest, but then this girl scoffs at me with an attitude and says, "That's BULL**! Obviously height and weight don't make a difference! Read a science book!" (lol?)

The fact that she missed that I was clearly joking notwithstanding (it's called pep talk, lady), after thinking about it some more in the locker room with my buddy I actually wasn't even sure what the answer to the question was. That is:

What are the (intrinsic*) factors which influence how challenging a particular exercise is?

*intrinsic to the nature of the body as opposed to how one uses it

Definitions:

I like to think that I have a very solid foundational understanding of biology, but this goes beyond the basics into ATP expenditure, muscle fiber theory, etc.

What is "challenging"?

First, we have to define what it means for an exercise to be "challenging". While there is certainly a psychological aspect to this, I would prefer to avoid that and stick with the pure biological definitions. Perhaps, an exercise is more challenging for person A than it is for person B if person A has to expend more energy proportional to their size than person B. I'm not sure this is the best way of looking at it but I obviously can't use something like "If person B expends more energy" because a bigger person will always use more energy than a smaller person quite naturally. The question is whether the bigger person's naturally bigger muscles 100% make up for the additional weight they have to lift to counter their own body...

Intrinsic factors vs non-intrinsic factors

I'm not looking for factors which affect how challenging an exercise is which are not innate to the biological system itself. Stuff like whether I had enough sleep the night before or are eating a proper diet — these factors are not relevant here. I'm assuming all these factors (which are relatively controllable) are otherwise equal in all comparisons of performance.

My current thoughts:

Height

Height—on the face of it—doesn't seem like it would too significantly affect an athletes performance, but I'm not totally sure. Yes, the oxygen is thinner up there, but that's insignificant, but my heart has to pump blood further to reach distant parts of my body. Is this somewhat of a factor? Unless heart strength scales proportionally with height (does it?), this seems viable.

Number of muscle fibers

It wasn't entirely clear to me reading basic skeletal muscle articles whether people vary significantly in the number of muscle fibers they have, and whether this has something to do with height or build.

Type of muscle fibers

Do taller people have, on average, a particular type of muscle fiber more than another (fast twitch vs slow twitch)?

Cardiac muscle strength vs body size

It is not clear to me whether the heart muscles increase in strength proportionally with body size. In fact, that so many large individuals (not simply fat, but big tall and otherwise healthy individuals) tend to have cardiac issues seems to attest to the fact that larger people put more strain on their hearts than smaller individuals (on average).

Other factors I'm missing

I'm sure there are other factors involved. If I think of others off the top of my head I'll add them to the list.

That's all I got. Help me out here. Thanks :)

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migrated from biology.stackexchange.com Jan 27 '12 at 11:49

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2 Answers 2

Physiology does in fact have a lot to do with how hard or how easy an exercise is to learn. Even more so when weightlifting is involved. While height is a factor, the real determiner is the length of your limbs in proportion to each other.

Squats

Squats favor people with shorter femurs. In general, shorter people have short femurs and taller people have longer femurs. However, that's not always the case. We've all seen people with shorter torsos and the legs make up the difference in height.

Essentially, to reach parallel, the crease in the hip has to go below the top of the patella. The longer the femur, the further down you have to go to accomplish that.

Deadlifts

Deadlifts favor people with longer arms. In general, shorter people have shorter arms and taller people have longer arms. The key here is that the longer arms help you get your back in a stronger, more favorable position, and you don't have to lift the bar as high.

Bench Press

Bench press favors people with shorter arms and larger chests. In general, this applies to shorter people.

In essence, a larger chest minimizes the distance down the bar has to go to reach the bottom of the movement. The shorter arms minimize the distance the bar has to go up to achieve full range of motion and lock out.

What's Easier Doesn't Mean Stronger

Simple physics demonstrate that just because an exercise is easier doesn't mean you are doing more work. The idea behind weight lifting is to generate more force to move heavier weights. In the world of Olympic lifts, the goal is to generate more power to move heavier weights in shorter amounts of time.

Example:

Joe is 5'4", and at full lock out on a deadlift the bar is about 20" off the ground.
Fred is 6'4", and at full lock out on a deadlift the bar is about 27" off the ground.
If they both lift 250lb, who has to generate more force? (answer is in foot-pounds)

20" = 1-2/3 feet
27" = 2-1/4 feet

Force = Distance * Mass (simplified to weight in this case)

Joe's Force = 416 ft-lbs
Fred's Force = 562.5 ft-lbs

The physical dimensions of both of these lifters is the only thing that changed. They both deadlifted 250lbs, but Fred had to generate more force to do that because lockout was 7" taller than Joe's.

In terms of science, physiology does in fact play a big role as to what is hard or not. However, lifting is as mental as it is a physical endeavor. The shear force of will needed to push heavier and heavier weight is what leads to recruiting more and more of your muscle to do work (central nervous system).

So, for your female compatriot, her comment about science is wrong, but the spirit of what she was telling you to do (stop making excuses and get your mind in the game) was right.

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stop making excuses and get your mind in the game - in total agreement –  Meade Rubenstein Jan 27 '12 at 13:44
    
Technically Force = Mass * Acceleration, but you obviously need to do that to cross any distance. If you were to make the same movement in the same time, you'd need to accelerate more and thus you would have to apply more force. If you kept the force the same, you'd have to perform them slower (which isn't necessarily easier either) –  Ivo Flipse Jan 27 '12 at 16:23
    
+1 solid answer :) although just to nitpick, your last sentence suggests you (and meade) misunderstood the scenario slightly. :P I was not making an excuse (I was outperforming him with proper technique whereas he was being a bit sloppy); my verbal jab was to get him to stop slacking. :) –  stoicfury Jan 27 '12 at 17:08
1  
Sorry about that... –  Berin Loritsch Jan 27 '12 at 20:58
    
@Ivo Flipse: I believe you provided the definition of power. Power is even more telling when you are comparing Olympic lifts to the slower "power lifts". Moving a barbell the same distance, but at a faster rate of speed requires more power. –  Berin Loritsch Feb 3 '12 at 18:10

I think this is a good question to ponder after a good workout. Does height/weight differences affect the person's ability to perform an exercise - definitely yes, depending on the exercise. I think squats are easier for shorter people, deadlifts for taller people, benching for people with shorter arms...but a tall person could out squat a shorter person based on MANY factors: genetics playing a significant role here in regards to muscles, stamina, muscle fiber distribution/type, energy processing, etc.......I think if you look only at height/weight your looking at a small set of potential differences impacting performance. OVERALL - I think each person is different in many ways BUT similar enough to be able to perform the same as anyone else if enough dedication/determination is applied. I've seen to many 'challenged' (missing limbs, post-cancer, etc.) people out-perform genetically gifted people to realize, like most things, it's 90% mental.

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