Hamstrings had me awake last night

[Suwannee Dave]

Last night, I woke up around 3am like I usually do, (being 67), and instead of worrying about lime scale in the pipes I started thinking about hamstrings. How is it (I thought) that these muscles can be involved in both knee flexion and hip extension. How do they know which one to do. Then it occurred to me that of course the muscle don't know anything and it may be because the hamstrings (unless one is on a leg curl machine) do not work in isolation. The brain does not command the hamstrings to do knee flexion or hip extension, it commands a gait for walking or running, a squat, a deadlift, etc. and the hamstrings fulfill their part in these movements as required, with the quads, erectors, glutes, etc. also doing their part in concert. Am I on the right track here? It may be obvious to those trained in exercise physiology but it seemed like a revelation at 3am.

[Mark Rippetoe]

I have all kinds of brilliant ideas when I wake up about 4 hours after I go to sleep. The clarity is sometimes astonishing enough that I write these things down. Later, when I'm actually awake, I am disappointed. I know how you feel.