Stretch Reflex & Playing the Edge
Some movements involving voluntary muscle contraction happen automatically as a reflexive response to intended movements or external stimulation. Here the body is acting before you can think about it. When a muscle contracts in response to stretching within the muscle, this is called a stretch reflex. With eccentric contraction—for example, the hamstrings while folding forward into Uttanasana—it is easy to generate a stretch reflex. In folding forward we ideally relax the hamstrings, allowing them to stretch more easily.