Why Body Weight and Relative Strength Matter

The picture below is a simple mathematical representation of why pounds are not created equal in sport.

In the above theoretical situation, there are two athletes. One weighs 90kg the other 100kg. Let’s assume that they both start from a static position (sitting on a box) and jump straight up into the air. For both athletes, the jump took 1 second to perform (yes very slow) and they both left the ground at 4.4 m/s. Thus, they both jumped the same height. However, the question is, how much more force did the heavier athlete have to create?

Well, the net impulse difference was 44kgs between the athletes, despite only a 10kg difference in weight.

Why does all of this matter?

When you put on weight, it’s not a 1:1 ratio of kgs to force needed to move. This makes things a little tricky because being strong typically involves increasing muscle mass.

In my opinion, this is where the whole “strong enough” debate comes from. By default, strength training adds weight, which in turn can be negative. It may get to a point where lifting more weight requires more weight to be put on. This is the point where “risk vs reward” comes into play. Is getting them stronger at the cost of adding weight beneficial? For some sports, absolutely. For others, maybe not.

In a perfect world, where adding strength didn’t mean adding mass, there would never be “strong enough”. However, we know this is not the case.

Note, this is why you don’t see triple jumpers carrying around extra mass. They have to be strong as hell off one foot, which mean every pound added is magnified when placed on one leg.

In short, relative strength matters.