This YouTube video by martial arts instructor Jesse Enkamp teaches us a new and fast way of improving our flexibility. He calls it reciprocal inhibition, and it’s based on the fact that all muscles are part of opposing pairs. The biceps are paired with the triceps, the quads are paired with the hamstrings, the chest is paired with the back, and so on. If we want to make a particular muscle more flexible, we should gently work its opposing muscle. Enkamp explains the drill, and demonstrates it with a few examples.