Science has shown that holding stretches for periods of time referred to as "Static Stretching" can actually cause the stretch receptors at the end of the muscle fibers to cause the muscle to contract, as a stretch reflex, therefore shortening the muscle and making them tighter. What often happens in slower asana holding yoga styles is that the student or practitioner will hold a yoga pose inducing a very deep stretch for a period of time and the lengthening isn't coming from the muscle, but from the stretching and damaging of the supporting ligaments causing instability in the joints. This dangerous hyper-mobility can cause repetitive injury to the unstable joints. Pilates uses a form of stretching involved in a full range of movements referred to as "Dynamic stretches" to allow the muscles to lengthen through healthy movement patterns to increase flexibility without causing damage to the ligaments and joints. It does not encourage but actually works to correct hyper-mobility by building up the tiny joint stabilizing muscles that surround the joints. This is why Pilates is often used in physical rehabilitation of injuries, including those brought about or caused from Yoga.