ANATOMY GEEK THOUGHT OF THE DAY: We often think of a muscle contraction happening only when a muscle *shortens*. But muscles work just as often as they lengthen - picture your hamstrings and the way they lengthen while they work to control your swan dive into uttanasana (standing forward fold) in yoga. When a muscle works as it lengthens, this is called an *eccentric contraction*, and we move this way all the time in our normal human movements.
One of the core rules we tend to learn in our yoga teacher trainings is that after we've "worked" a muscle or muscle group, we should stretch that muscle group to "balance it out". But because muscles can and do actually contract through all of their ranges (short, long, somewhere in between, etc.), is it skillful to consider the opposite of a muscle contraction a *stretch*? Do these two "balance" each other out? If it turned out that they were not necessarily opposing actions, would this change the way you sequence your yoga classes at all?
Enjoy pondering this one, and feel free to let me know how it goes!