Hamstring swings:
Prone to hamstring pulls or tears? According to Running Research News, this exercise puts the hip through a full range of movement with no impact, and warms up the hamstrings. Stand side-on to a support and, with your knee bent, lift the leg up to hip height and swing it up, down and back in a circular motion, the leg almost fully extended at the end of the backswing (see bottom two pictures). Do 20 on each leg, increasing the range and speed with each one but always maintaining control.