How does muscle length and range of movement correlate?

Question

First, I'm free to admit that I don't know exactly where along a limb the muscle mass really is and also that I have a very simplistic view of "short muscle" - so if I'm conceptually wrong, please correct me or point me to some links.

When I was doing Muaythai, I think I had strong legs, specifically the muscle responsible for stretching the leg (quadriceps?). This muscle also seemd to be bulked on the upper end of my thigh, away from the knee. The range of movement of what I did with the leg was typically very close to a stretched position. Since I started going to a gym (and doing presses with the leg with a higher range of movement), I notice that my body builds muscle nearer to my knees ( or there's a new fat-deposit) - a good thing in my book, because I hope for more stable knees.

Is my observation plausible? Can this be generalized for the training effect of movements with different ROMs?

Answer 1

I suspect that you previously noticed more muscle near your upper thighs because your quadriceps were not very developed except for the rectus femoris (one of the 4 quadriceps muscles), which also acts as a hip flexor that would be used to develop a lot of the power during Muay Thai kicks and knees. (This is a quirk specific to the Muay Thai style of roundhouse kicks.) It would be developed disproportionately to the other quadriceps unless you were doing strength training.

The muscles you're seeing develop now are the vastus lateralis and medialis. These are two other quadriceps muscles with a bulk of their visible mass closer to the knee.

However, this doesn't generalize well. The idea of muscle building close to the proximal joint vs distal joint is very specific to the motions you happened to be doing and the structure of the quadriceps (because they're actually 4 different muscles).

What does generalize is that you will get strong in the range of motion that you exercise. You were previously exercising Muay Thai kicks, which demanded strong hip flexion, so your upper quadriceps got strong. Now, you're exercising strength being pushed through your legs to the ground (or leg press platform), so the rest of your quadriceps are getting strong.