A recent study looked at the effects of a stretching regimen on range of movement in the thigh. The participants did a supervised stretching program four times a week for two weeks. They warmed up for a few minutes and did 10 squats. Then they did two sets of stretches on each leg, for a total of 80 seconds per leg. They did the same stretches each time.
After the two-week program, thigh stretches felt less intense. However, there were no significant changes in range of movement.
It may be that the stretching program was not rigorous enough to improve range of movement. Interestingly, when participants were told to stretch until the feeling was as intense as it had been before the stretching program, range of movement increased 15 degrees. These results suggest that stretching can and does improve range of movement. Be careful to avoid stretching too forcefully, though. A physical therapist can design a good stretching program to help you get the maximum benefit.