Would you believe only 60 seconds? That's what researchers found. This study had people around 85 years old stretch their hamstring muscles for 15, 30, or 60 seconds. The 60-second group's flexibility went up nearly twice the other groups. This also results in better mobility, greater ease in bending over, and less back pain. This notion of stretching and holding the stretch is actually about 5,000 years old and is one of the principles of Hatha Yoga. In all of the Yoga positions, you hold the stretch while you keep breathing into the tension in the muscle.
I love it when a 5000-year-old system gets validated from modern research. My only question is how did they figure these things out 5000 years ago?