At 6’4″, I’m tall. I started lifting weights with other guys at 13 years old. When you’re tall, it takes about 8 seconds to realize long limbs don’t help you standout in the weight room.
As a tall person, rummage through the exercise science world a bit and you invariably run into,
As a reminder, force is made of how much mass an object has, and how quickly we accelerate the object. Provided a taller and shorter person lift the same weight at the same acceleration, because a taller person needs to move a barbell further than the shorter person, they have to do more work. Thus, it’s harder for a taller person to lift as much as a shorter person.
That’s often the end of the discussion, but it never jived with my weight room experience. Particularly in college when I was playing football, the taller lifters tended to lift together. Yes, it was harder for us, but it seemed significantly harder.
A guy who was only a few inches shorter seemingly was wayyyyy stronger than he should have been, just based on those few inches.
Here’s what I mean. Say we have two lifters:
- Shazam is 6’2″, 1.88 meters
- Ferguson is 5’9″, 1.75 meters
Alright, now let’s say they’re both lifting 100 kilograms. To keep it simple, we’ll ignore limb lengths and simply use their height as the distance they’re lifting. We’ll say they’re lifting at 10 meters per second^2.
- Work = mass * acceleration * distance
- Shazam’s work = 100 * 10 * 1.88 = 1880
- Ferguson’s work = 100 * 10 * 1.75 = 1750
- 1880 / 1750 = Shazam is doing 7.4% more work
Generalizing, if we’re talking a bench press, if Ferguson’s max is 400 pounds, then Shazam’s max should be 370 lbs.
It just never worked out that way. Unless the taller dude was way heavier, it always felt more like a 30% difference, if not more (tall guy could only bench 300 lbs).
–
What we all already know- size matters
I found the men’s 2016 olympic weightlifting rankings.
-> I’m often biased to males with these types of articles. That’s only because men have been doing the activity longer, almost always have a much larger sample size, and drug use is more consistent.
There were thousands of them.
-> I wanted to use powerlifters to make this more pure strength oriented as olympic weightlifting necessitates much more speed, but finding powerlifter heights is impossible. Weightlifting is much more popular, where it’s easier to find info on the participants.
I arranged the lifters by total, finding the top ~50 respective heights.
Next, I divided strength by weight, and found those top 50 heights (roughly).
That is, I found the heights of a bunch of guys who are strong in absolute terms -the most amount of weight lifted- and guys who are strong in relative terms -the most amount of weight lifted relative to how much a guy weighs.
The reason relative strength is important is because taller guy’s often make up for their height by being heavier. We wanted to cancel that factor out. That is, does how tall you are affect how strong you can be, no matter your weight?
All the data:
First, height vs absolute strength:
This might be initially surprising. What we see is as height goes up, so does strength! But this is misleading. Like we went over, the tall guy’s are making up for their height by getting heavier. Sometimes, demonstrably heavier.
When we account for bodyweight:
The exact opposite is found. Get taller? Get weaker.
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How much weaker?
Let’s look at these two lifters:
- Orange = 1.97 meters tall and 3.01 strength / weight
- Pink = 1.5 meters tall and 5.0 strength / weight
Thinking about our work formula again,
- Our orange lifter is 31% taller, so we could expect them to be 31% weaker, relative strength wise
- (they have to cover a 31% greater distance)
- However, 5 / 3.01 = 1.66.
Our shorter lifter is 66% stronger!
“That’s only one guy.”
Arranged by height:
- If we average the height of the top 50 guys we get 1.81 meters.
- If we average the height of the second 50 guys we get 1.61 meters.
- Based solely on height, that work difference is 12.4%. (The first 50 taller guys have to do 12.4% more work for the same lift.)
- If we average the strength to weight of the first 50 guys we get 3.64.
- If we average the strength to weight of the second 50 guys we get 4.78.
- The second 50 guys are on average 31.4% stronger.
I think at this point it’s obvious there is something besides straight mechanical work going on here. For instance, why are the second 50 guys ~20% weaker than physics tells us???
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Explanations
Volume vs area
This is the most studied element. Muscle strength correlates well with cross sectional area. Body mass correlates well with body volume.
- Area is length * distance.
- Volume is length * distance * depth
If we view muscle as a rectangular tub, then as the tub increases its dimensions, volume goes up quicker. For example,
- Area starts at 2 * 2 = 4
- Volume starts at 2 * 2 * 2 = 8
If we increase the length, width and depth by 1,
- Area = 3 * 3 = 9
- Volume = 3 * 3 * 3 = 27
Volume is going up faster than area. The area went up roughly double, where volume more than tripled.
Thus, because area relates to strength and volume to body mass, body mass goes up quicker than strength. This is known as allometric scaling. Greg Nuckols wrote a good piece about this,
-Who’s the most impressive powerlifter?
He mentions allometric scaling does not hold up well for super heavyweights (in powerlifting). He and others have related this to body fat. Idea being heavier weight classes get to a point where they are not increasing body fat proportionally with muscle. If they were 8% body fat at 80kg, and 90kg, and 100kg…but then they’re say, 12% at 120 kg, that throws the expectation off.
However, Greg uses a really small sample size (10) with powerlifters.
-> To be fair, Greg was primarily looking at the record holders, and trying to extrapolate that to allometric scaling. But small sample size nonetheless.
In our weightlifting sample allometric scaling doesn’t completely flatten out the data,
And it’s still awfully related to strength to weight ratio,
Allometric scaling also doesn’t directly measure the impact of height, yet we’ve seen height is very related to total strength.
In the below sample of NFL players (from this post) we can see as players get heavier, they get fatter:
However, while strong, the relationship weakens when we look at height vs weight:
In other words, something about being taller is causing a decrease in relative strength, but it might not be solely body fat, because the relationship between height and body fat is strong, but it’s not like the correlation is 1:
Unfortunately, I don’t have the body fat percentage of a hundred weightlifters, but I imagine the relationship would be similar. Particularly considering the height and weight relationship is so analogous:
And while sometimes conventional allometric scaling works very well,
sometimes it doesn’t. Others have pushed back saying allometric scaling isn’t as simple as only looking at area vs volume,
In that study, they discuss issues once getting above only 90 kg. (Far from a super heavyweight.) Where once above that mass, the effect of mass is increased more than you’d expect by the area and volume logic. 90kg isn’t very big. If you’re a tall dude with practically any muscle, you’re going to be that heavy or more. It’s possible what many have been automatically reverting to an explanation of body fat is also part of body height- what we’re fully attributing to weight may also be partially explained by height.
-> One theme of the studies I’ve seen is with football players and powerlifters, allometric scaling looks to work better than with weightlifters. One reason I could see that is the height differential with football players and powerlifters isn’t going to be as great as with weightlifters.
In weight lifting, you have guys from just below five feet to just over 6’5″. Anecdotal, but my experience with football and powerlifters says they don’t vary that much. (You don’t see five foot football players or 6’5″ powerlifters.) So because the heights are closer together, you don’t see the impact of height as much.
Thus…
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Two other factors?
Mechanical work clearly doesn’t explain everything. Biological scaling gets us far, but perhaps not all the way. Really, we haven’t mentioned anything yet directly explaining the physiology of height. We’ve indirectly gotten at it by examining weight, but surely height could have its own explanation, no?
Here are two ways I could see explaining the rest:
- Nerve conduction time
- Blood supply
Nerves can only conduct so fast; blood can only travel so quickly.
If you’re 10 inches taller, that’s 10 inches more a signal has to travel down a nerve. (20 inches more if you include getting a signal back!)
Same goes for blood. If the heart gets a signal it needs to pump more or increase blood pressure,
- As we already said, that signal takes longer to get there
- The heart has to pump that extra blood / pressure further
–
Overall, we have some solid theory why we DON’T see tall people doing particularly well in events based on
- Moving their own bodyweight
- Speed
You see LONG people, that is, long limbs, but you can have 6’4″ limbs on a 5’8″ body.
Usain Bolt is perhaps an exception, at 6’5″. He’s actually a quasi exception- he’s notorious for a bad start, and he really shines towards the endurance part of the 100 meters. (Though endurance runners, like marathoners, skew short.) Others have stuck with him well up to that point:
It would be interesting to know how Bolt is overcoming his height issue. Perhaps he say, has an unusual nerve conduction velocity, allowing his height to not be a detriment. Or, in fact, being taller means having a bigger heart. Maybe Bolt’s heart is big enough to negate the blood traveling factor.
-> Other potential factors:
-Fast twitch ratio
-Muscle density
-Muscle / tendon lengths / attachments
-His surface area to volume ratio (this dictates how easily you can dissipate heat, potentially the reason whites don’t perform as well as blacks in running)
-Intelligence with training (e.g. staying healthy)
-Drugs
That doesn’t mean, even on average, that tall people are doomed in sports. Obviously not. In basketball, it doesn’t matter how quickly you can send a nerve signal if you can only get nine feet in the air. Too short, and you can only weigh so much before getting fat. It doesn’t matter how quickly you accelerate when there’s no mass in your ass. There are also other advantages of long muscles, which we’ll get to in another post.
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Brief tangent
We can see above
- Predicting performance in sports is easy
- Predicting performance in sports is impossible
If your criteria for performance is strength to weight ratio, or you’re in a low weight class, it’s easy. You NEED to be short.
If your criteria for performance is absolute weight lifted, it’s easy. You NEED to be heavy, which means you need to be taller.
If you’re trying to predict basketball performance, 6’8″ vs 5’8″? Easy. 6’8″.
When we’re looking at extremes, it’s not that hard.
When we’re looking at the middle, which by definition is most people, it gets much harder.
When you’re 5’8″, even if you have the most fast twitch muscle available, the fastest nerve conduction velocity, in basketball, it’s borderline impossible to overcome your height.
But when you’re assessing 6’5″ vs 6’2″, everything gets way murkier. You might be able to assess height, strength to weight, and nerve conduction velocity, but putting together an algorithm that properly weighs those variables, oh, and probably another 1000 variables we haven’t discovered yet, or just don’t have data on, ain’t easy.
One of the hardest parts of studying taller guys, and thus, the heavier guys, is there are not as many of them. (90% of the population is 6’2″ and under.) What if one reason the smaller guys standout with strength to weight ratio is simply because there is more of them, thus more competition, thus higher totals? After so many years and so many people, coupled with the fact the tall guys have the incentive of being the strongest person in the world (remember, taller = stronger), I find this to be an unlikely explanation, but it has to be on the table.
“[one hypothesis] the 2/3 exponent approach tends to “bias” [against] those in the extreme weight classes is because far more competitors are found in middle weight classes (not surprising as M tends to be normally distributed in the population). As these lifters have more competition, one should not be surprised when middle weight class lifters tend to receive the highest [allometric] scores. Furthermore, when Batterham and George eliminated the heaviest lifters (those who have no upper limit of M) from their analysis, the resulting exponent for M was 0.68, nearly identical to 2/3.”
A simple index to adjust maximal strength measures by body mass.
What isn’t brought up in that quote though is when eliminating the heaviest lifters, you also eliminate the tallest ones!
This is why sports teams, to this day, have a terribly hard time predicting players. There is a great story in The Undoing Project about Daryl Morey, who is from MIT and has dedicated his life to predicting player success. He works for the Houston Rockets. DeAndre Jordan was a player every team passed on, including Morey, yet who’s become a NBA standout.
Turns out Jordan didn’t like his college coach and hated school.
Yep. That simple. Right coach, doesn’t have to deal with school, boom, now he fits into the predictive model.
We often assess these variables with the caveat “all else being equal,” but all else is never equal.
And even with all the measurables quantified, it’s debatable whether it’s even possible to reasonably predict the human mind.
Chris
January 24, 2018
Hi, great work!
I dont agree with one of the key assumptions though: “Work” is pretty irrelevant for 1RM feats. The lifter may use some more energy – but energy isnt limiting. The torque at the sticky point is. And that is a function of muscle mass (which is related to weight and height as in your article) and the levers.
Other than that, good job!
b-reddy
January 25, 2018
Hey Chris,
Thanks for the nice words.
Per the work energy theorem, work = energy. Torque is proportional to work. So saying torque is limiting is saying work is limiting i.e. if you lessen / increase torque, you lessen / increase (rotational) work.
Might be helpful:
http://spiff.rit.edu/classes/phys211/lectures/rotke/rotke_all.html
https://b-reddy.org/2013/09/05/a-progression-to-lifting-your-arms-overhead-pain-free/
I believe you may be trying to make a chemical energy argument, rather than a mechanical one. I’ve heard people try to make the argument a maximal lift only lasts ~five seconds, so it’s not constrained by (chemical) energy, due to e.g. ATP reserves. This is also a dubious argument, but beyond the scope of a comment. Have a post about it coming eventually. Long story short, elite 100 meter sprinters start slowing down before seven seconds i.e. they’re fatiguing, and they aren’t holding a sustained contraction like a 1 rep max is. (Not to mention there is research showing a maximal contraction can only last a “few” seconds.)
Chris
January 27, 2018
Yes you can calculate energy by work and by torque. However, you used the argument of total work (due to longer distance, not torque) that taller lifters can lift less. As in “less weight on the bar” and “relative to body weight”, however relative may be calculated. And its my point that that does not depend on the work done, but specifically on if the sticky point can be overcome – and thats in turn a question if the generated force can overcome the external torque at the sticky point.
b-reddy
February 2, 2018
Curious what your definition of sticky point is?
Chris
February 2, 2018
Hi!
The same as everyone´s: The point of slowest bar speed. It usually is a bit past the actual hardest point (which in turn is the point where required torque and force capacity are closest to each other), because in most movements there is a bit of momentum.
b-reddy
February 2, 2018
-Sorry if this is pedantic, but slowest bar speed can’t be the definition. As, when the bar is transitioning from down to up, the speed is, momentarily, 0.
Yet conventionally, the sticking point is never referred to as this point. It’s always once the bar is moving up, as you alluded to. The bar moves up, then slows down, then moves faster again. The slower point is typically referred to as a sticking point, but that’s vague (see next point), varies by person, and is not the true slowest part of the total lift.
-Are we talking a single point? If so, you’re saying isometric strength limits lifting ability, which can’t be correct. If we’re talking moving the weight through a distance, then we’re saying work limits performance. (I understand you’re differentiating between force and distance). Then, are you saying everyone has the same relative sticky point? For instance, it’s always three inches of motion of a given lift? Or is it say, 10% of the lift? If it’s percentage based, then a taller person will have a greater distance of a sticking point.
Again, sorry if this seems like minutia, but a proper definition here is critical, and I’ve never seen one for sticking point. I get what you’re saying in general, but we’re talking a very specific element now.
-Are taller people’s sticky points different than shorter people’s? If so, how? (While keeping in mind, if the taller person’s sticky point is a greater distance, then we’re back to considering work, and the distance element of it.)
-Why are we focusing on torque? Torque is commonly referred to when rotating an object. In bench pressing, squatting, deadlifting, in a great deal of lifting, we’re barely rotating an object (bar path is more or less straight). I don’t see why using linear kinematics isn’t sufficient here, as we’re referring to the object, not the human’s joints.
-Even considering torque, if we’re saying a taller person has longer limbs, thus longer moment arms, that’s the distance element of generating torque. But you’re saying this changes the force element?
Torque = force * r. Force = mass * acceleration. I used an example of a taller person lifting the same mass at the same acceleration. You’re saying the taller person needs to generate more force. Why? Where is this extra force coming from? The mass (kilograms on the barbell) and acceleration (gravity) acting on the object have not changed. Why do they need to generate more force to lift the same weight at the same acceleration?
-Despite the above, I never said work was the limiting factor with being taller. I made a case work can’t be the factor, that it’s a smaller factor than physiology.
I’m sorry man, not trying to be rude. I’ve been sick lately so maybe I’m not thinking clearly. I have a feeling we’re just defining some things differently, but I’m not getting what you’re trying to say.
Chris
February 3, 2018
No problem, no offense taken and get well! These are interesting questions.
– Yes, of course the sticky point is slowest speed in the concentric portion. The eccentric cant be the hardest point, and neither can the change from concentric to eccentric due to the the stretch reflex (which according to one study doesnt dissipate completely until a few seconds; thats why even a medium-length pause command in the bench press, for example, creates the sticky point directly at the start of the concentric). For a more scientific measure, you could identify the biomechanically hardest point by discussion of the function. Its the greatest negative change in v (steepness), because the greatest deceleration means there is the greatest force deficit. And a bit later results the slowest point of the lift.
This is how it looks like: http://www.mdpi.com/sports/sports-05-00046/article_deploy/html/images/sports-05-00046-g001-550.jpg
– As you can see in the graph there is one point of minimum velocity, but of course you can describe a more fuzzier “sticky region” for the beginning of the most drastic change in v till the rise of v after the minimum point of v. Regarding isometric strength: Yes, a maximal lift is at the extreme end of the v-s-curve and you could say that is dependend in the sticky point/true hardest point of the max strength at this point. This is btw different in weightlifting, which are maximal power, but submaximal strength lifts (see my point below).
I dont know of any study that investigated sticky point differences depending on body height. I can only say that its clear maximal strength lifts are dependend on maximal strength in the most difficult point, not strength over the whole distance, because its visible from the different v and accompanying accelerations that 95% of the lift is not at the risk of failure (i.e zero to negative v).
Yes, there is individual variation for sticky points. Everyone has different leverages, neuromuscular activation – and simply training history (if one trains his triceps heavily, the other one his pecs – then they probably will have different sticky points in the bench press).
– Oh, its always torque. Thats why longer bar paths in taller people doesnt matter much. I think thats the crux of the discussion. Its torque requirements because thats what happens at every joint. Only the combinational work of joints resutls in linear bar paths. But the requirements (and success or failure) happens at one joint if the bar path cant deviate much from vertical (and it often cant in maximal lifts – also a difference between weigthlifting and max strength).
– From theoretical expectations in Greg Nuckol´s article to your discrepant findings: Well, its important to really study maximal strength. That is, not weightlifters. And also not sprinting or any other activity much different to quasi-static maximal strength as in powerlifting.
That aside, even then you would expect medium height lifters to overachieve allometric scaling and taller than average lifters underachieve in a sample – simply due to baseline sample size differences. Btw, therefore I expect that to change slowly as the average population height increases. If we do the same calcutlations on a group of elite powerlifters in twenty years, a 185cm+ vs 175cm comparison will be less unfavourable for the 185cm+ than it is now. But as of now, almost all highly lucrative sports draw the already fewer taller athletes to them. Soccer is an exception on an international level – but who plays soccer in the US (where most powerlifters in studies hail from) or China and Iran (to name a few traditional strength sport countries)? And soccer also doesnt rely as heavily on strength characteristics as Amercian Football. So less inter-sports competition about talents there.
I guess Ockham would be satisfied with this simple explanation. 🙂
b-reddy
February 6, 2018
I appreciate the clarification. I still think we’re dealing with this too abstractly. For instance,
“Much” is a subjective term. Using the example I made in the post, a 7.4% difference can be enormous or shrug worthy, depending on the context.
But never mind height. Bar path length matters enough powerlifters use wide stances in squatting and wide grips in bench pressing. This is particularly noteworthy because there is a joint health tradeoff.
Bar path length also matters enough people clearly have higher rack pull maxes than deadlift. Higher board press maxes than full bench press. That full squatters like to make fun of half squatters, despite having more of a stretch reflex in full squatting. That powerlifting is super anal about hitting proper depth. (By clearly, I mean the difference is noteworthy. It’s not like people have trouble noticing the discrepancy.)
I also disagree with the idea of only looking at maximal strength, as a great deal of maximal strength training is not e.g. single rep training. (You don’t train for maximal strength by only engaging maximal strength.) So whatever effect there is with bar path length in one rep, gets magnified when we look at multi-rep training. The higher loads you can use in training, the higher loads you can peak at.
So, if we’re talking comparing a guy who is six foot vs a guy who is 5’10”, just everyday people, similar levers, then sure, height, bar path length, isn’t much of a concern. But if we’re talking high level performance, just 1% differences can mean dominance.
Chris
February 12, 2018
Higher rack pulls and higher board presses and half squatting are all easier primarily because their maximal torque is reduced in comparison with the full ROM exercises, not because the bar path is shorter (which is merely a byproduct of that). For example, you can shorten the bar path via only the bottom 2/3 portion of the squats – it will still be as hard. And if your sticky point in the DL is not at lockout, you could do deficit deadlifts (increasing leverage in the bottom position and thus torque for the hip extensors/spinal erectores) just till above the knee and they will be even harder and you will be able to lift less, although the total bar path is even shorter.
Sets with multiple reps as well are dependend on the nature of the sticky point, i.e. if you can overcome that point X times and finish the reps/set, not the 95% of the rest of the bar path, including whether the bar path is longer. Energy expenditure is not a problem with low to medium reps, and in addition to that, taller lifters are expected to have more muscle mass, so they have more energy capacity (ATP, glycogen, Cr). What they admittedly then will have to do more is eating, but it stands to debate if that is a bad thing in the modern world of overweight… 🙂
b-reddy
February 13, 2018
Sure, but why is the torque reduced? They’re lifting the same mass at the same acceleration, which means force is the same. The distance component of the torque equation is what is lessened, thus lessening the overall torque. You can’t lessen the distance and say it doesn’t influence torque (or work), just like you can’t reduce the mass and say it doesn’t influence torque (or work).
I gave some references for the energy concern earlier, such as needing to differentiate between mechanical vs chemical, how long maximal contraction can last, examples of how quickly endurance becomes a factor during all out activity.
We’ll just have to agree to disagree on this one. Appreciate the conversation.
Chris
February 13, 2018
No, the force requirements in those easier lifts are reduced because of the different maximal torque: They simply cut out the hardest point concerning torque of the greater ROM movements. For example quarter squats cut out the thighs parallel position of a competition squat. High rack pulls cut out the first quarter of a conventional DL, where torque requirements of the hip and back extensors are greates because of the trunk position. I purposefully constructed the example of a deficit (think just 5cm) deadlift that is only executed till knee level to demonstrate that even with a smaller total distance you can have a harder lift. Because maximum torque demands matter (and if your strength can meet those demands), not torque over distance (i.e., work or energy).
Even clearer: Take a 15kg dumbbell. a) Extend your elbow fully and move your arm in a frontal raise 10cm up, starting from a dead position 5cm below the horizontal plane parallell to the ground. Now take the same weight, and either b) do the exact same movement, but elbow not extended or c) only extend the arm from 0° to 85° (just short of the horizontal). in front of you, with elbow extended as in a). What was more difficult? The shorter distance of a) – or the longer distance of b) or c) ?
As you are aware of Greg Nuckol´s work, look up the analysis of the squat, bench and deadlift on his site. Difficulty of a lift is all about maximal torque at one point or a very narrow range. Not maximal work, not distance covered.
I am sure on this point – you can ask any biomechanist about that.
The second point, whether a larger distance, i.e. more work exhausts the energy systems earlier, AND this exhaustion is of practical relevance in strength and hypertrophy training (not endurance training or even strength endurance) is debatable and dependent on various factors like muscle mass involved and rep numbers. As I said above, taller lifters have more muscle mass, so they also have more energy stored. But if that doesnt equal out, I can see your point being meaningful in certain strength endurance scenarios like for example in CrossFit competition exercises.
b-reddy
February 16, 2018
As I hit on earlier, I think definitions aren’t lining up here. Hey, could easily be my fault. I’ll give this one last go definition wise, focusing on torque. This is not me trying to make a point or argue my way of defining things is the end all-be all. Rather, I’m attempting clarity at where I’m coming from.
Torque vs Force- I understand many jump to calling torque, force. Or using them interchangeably. I find this confusing, since torque is comprised of force. I’ve been trying to get us to teasing out the force aspect of the torque equation. When I’ve been saying force, I mean mass * acceleration.
Using moment arms to say “we end up generating more force”- provided all else stays the same, a greater moment arm means more torque, BUT, it does not mean more force from the force component of the torque equation. A greater moment arm does not automatically mean more mass or more acceleration. Particularly when talking about a non-living barbell.
Within a human, it COULD mean more force- more mass and or acceleration. But I explicitly stated an example of “same mass at same acceleration.” I could see how that didn’t also come across as “the human uses same muscle mass at same acceleration.” But the idea was nothing changes but the distance the bar travels (/ where the bar is acting on the person). In which case, the distance element is the causative factor; secondarily because more force cannot be generated.
If one wants to say a greater moment arm means needing to engage more force -mass and or more acceleration- that’s fine, but it’s not the example I was using. (In the article I explicitly emphasize how taller lifters can make up for their shortcomings with having more muscle, acknowledging a potential compensation.)
High bar vs low bar squat (or taller squatter vs shorter squatter)- a high bar squat means more torque is acting on the e.g. lower back. The bar is trying harder to rotate the torso forward. It does not mean more force is acting on the body, as mass and acceleration of the bar has not changed. The force acting on the person has not changed. The force acting within the person could change. (They need to have more e.g. mass to engage in the first place. Not a guarantee. Particularly if we are considering a taller and shorter lifter who have the same mass.)
Chris
February 16, 2018
Ahh, ok now it gets clear for me why you have been discussing with these arguments. 🙂
All right, Ive been sloppy with force vs torque, although that doesnt change my argument, but sorry for that.
Imo the point is that the internal force demands (what you described with force acting within the person) at a point or narrow range and joint (by torque) is crucial in lifting weights. Thats what I tried to explain with the deficit deadlift example and with the front raise example.
Youre right, for an external observer who puts a sensor on the barbell (or just models barbell forces without modelling the lifter as well), all what matters energetically is bar mass and distance travelled (against gravity, which it almost perfectly does in heavy compound/multi-joint lifts like the deadlift and squat). And it represents more work and energy if the barbell travels 5cm farther in taller lifters. But for humans that doesnt matter: Energy spent and work done may be energetically more in taller lifters, but its not automatically harder in taller lifters considering difficulty. That means, how much weight you can lift in practice.
Because difficulty means “difference of force capacity of muscle X at joint degree Y – demands at point X”. Thats why in your example, people CAN low bar squat more than high bar squat – because the low bar squat diminishes the force requirements for the quads. Which are usually the only muscle maxed out in a squat, around the point “thighs parallel”.
b-reddy
February 20, 2018
Glad that helped cleared things up. We’re more on the same page now!