You probably feel it in whichever muscle is weakest for holding the position and I'd guess there are a lot of muscles in use for that!
I'm thinking it is the rectus femoris. But is it getting tired because I never use it? Or is it getting tired because it is compensating for another weak muscle?
That exercise puts strain on the hip flexor, or iliopsoas. It tightens up from running or stuff like this. Called a runners thing. You need to stretch out the iliopsoas to relieve the pressure on the nerve running through the hip area. The best I found was the leg drop of one leg while lying on a bench while the other knee is pulled up to flatten the back on the table. Hold for 15", repeat. Do with both preferably.
George, I tried this stretch. Are you supposed to feel it in the leg that is hanging or the leg that is bent? II didn't feel it in either.
Also, how would pressure on the nerve cause the muscle to get fatigued during this exercise? Or am I missing something here? Thanks for your insight
"Why should I have to touch my toes? I never do that during a race."