I have become fascinated by the effect of different body size and shape on performance, both in sport and in the weight room. It is pretty obvious in some sports – the tall person is almost certainly going to do better in a sport like basketball than the short one. Not only is he taller, but she’s got a better reach. Height rules in many sports. But what about the weight room?
I watch a lot of great training videos. In addition to learning and being impressed with what some people can do in the weight room, I’ve noticed something else: many of these great trainers seem to be, well, a little vertically challenged (I feel like I’m on thin ice here!). It was a pushup video that really opened my eyes. The person in the video had a beautiful pushup, but it looked to me as though he was only moving his chest a few inches off the ground. Meanwhile, when I do a pushup, it feels like I’m lifting and lowering my body a few feet. I started to wonder if this was a legitimate concern, or if it was just my imagination. Was I just making excuses?
I began to think more and more about it. I thought back to when I spoke briefly with Dr. Stuart McGill at a seminar he gave. I mentioned that I am not very good at bench pressing, and he was quick to reply: “well no wonder; you’ve got those long arms” (probably a slight paraphrase as it was a while ago). It occurred to me that the weight room is a place where people who are relatively short, with short limbs, have a physical advantage over those who are taller. Now I might not make any friends with this statement, but take a look at your trainer – is he or she short?
This week I decided to put my body length theory to the test. Yvan is a friend of mine at the gym where I train. He has what I think are fantastic proportions for weight lifting: short arms and a fairly big chest. It is no surprise that he is very strong in the bench press, as you’ll see in this video. As you watch the video, take note of how much vertical distance the bar covers for a full range bench press.
Now take a look at how far the bar moves when I press, but disregard Yvan’s rambling in the background.
Actually Yvan does have a good point. He is training for a powerlifting competition, and so is using proper powerlifting technique. The goal of his lift is to push as much weight as he possibly can. The goal of my lift is to get stronger. I can get stronger without a big back arch, and since I am of the opinion that the big back arch is not ideal from a back health perspective, I don’t do it. I also bench with my arms at about 45 degrees from the body and not the T position that Yvan uses. This is for the same reason that I employ this in a pushup, which Bret Contreras and I wrote about in our pushup article for tnation.
You will notice the white dowel with red and white marker lines in the background of both videos. After filming this, we took measurements of how far the bar moves for Yvan, myself, and 3 others (Dave, Scott and Geoff). Here are the results:
As you can see, when I bench press, I push the bar almost twice as far as Yvan does (78% further to be precise). That’s a big difference. But what does it mean? To answer that, we have to think about what we are really doing when we lift weight. If we talk in terms of physics, we are doing work by using strength to apply force on the bar.
What is this force I speak of? Force = Mass x Acceleration (I suddenly had a flashback to my grade 10 science teacher, Mr. Marshall, saying FMA, as though it was a word). Taking this back to the weight room, the amount of force you exert to lift a weight is determined by the amount of weight you lift and by how fast you accelerate it. Force is measured in Newtons (N), and a Newton is equal to a kg*m/s2, or mass x acceleration. I think if you look at the videos, you’ll agree that we both lift at a fairly constant speed, meaning there is no acceleration upward, and so the only acceleration in the equation is from gravity, which acts on us all at a rate of 9.8 m/s2 (did I mention that I’m a recovering engineer?).
The mass and the acceleration are the same, the difference in how far we push the bar has no impact on the force we exert on the bar. This means Yvan can rightly say that he is stronger than I am in the bench press. A lot stronger. But what if we look at how much work we both do to earn that lift? In the world of physics, work means the application of force over a distance:
Work = Force x distance
Force = 45.4 kg (metric equivalent to 100 lbs) x 9.8 m/s2 (gravitional pull)= 445 N
How much work are we each doing for a 100 lb bench press?
Work Elsbeth= 445 N x 0.4064 m (1 inch = 0.0254 m) = 181 Joules
Work Yvan= 445 N x 0.2286 m = 102 Joules
Which means that for every repetition of a 100 pound bench press that both Yvan and I do, I do 78% more work than he does – exactly a 1 to 1 relationship to the difference in how far we push the bar. Why do we care about work if its just some silly term in physics? Because work is also an expression of energy. And for many people, energy expenditure is a big part of why we train. In this case, we are expressing energy in Joules (J); but you probably get a better picture of where I’m going with this if I talk about energy in calories (1 J = 0.239 cal).
My goal in this is mainly to satisfy my own curiosity, but also to remind people that we are often better off looking at effort than numbers, because you may well be exerting much more effort than someone else is to achieve what looks like a smaller accomplishment. This is such an important concept in the gym that I just can’t emphasize it enough.
If you see someone performing an amazing feat of strength in the gym or in a video, absolutely use that as motivation to help you work even harder to achieve your own goals. But please don’t make the mistake of looking at someone else’s results and thinking your own are not adequate. For all you know, you could be working harder than they are.
Elsbeth Vaino is an FMS certified personal trainer in Ottawa, Canada.