Vin,
You can prove it to yourself in minutes. Try this. Bend down and touch your toes. Notice which side the hamstrings are tighter. You will most likely feel one side pulling at the base of your butt more than the other side. Now lay on your back and pull that shortlegs knee up toward your chin. Grasp the hamstrings with your fingertips by wrapping your hands around your leg. Squeeze the hamstrings and straighten your leg so that it is vertical to the floor. Hold that stretch for two seconds, release the pressure and bend the knee to slightly contract the hamstrings and then repeat. The pressure should only be applied while the the muscle is stretched during the two seconds. Walk your fingers right up from your knee to your butt, each time stretching, squeezing and holding for ONLY 2 seconds. Do about 10-12 reps or until you feel things loosening up. If it hurts, you are squeezing and stretching too far! Let pain be your guide and do not think that this has to hurt you. Get up and walk around and then bend over and touch your toes again and notice the difference. Sometimes with injured tissue, it can take up to 21 days to re-program the muscle so that it stays longer but then the brain will help keep it there.