Detecting muscle spasm pains ahead of time is difficult if not impossible, but preventing them isn't complicated. Use a technique called Propioceptive Neuromuscular Facilitation or PNF stretching. Since PNF also strengthens muscle and improves flexibility, your hamstrings may benefit from this technique.

PNF Explained

PNF works by targeting a muscle -- in this case, the hamstrings -- and causing a contraction. According to the Stretching Institute, it was originally developed as a form of rehabilitation but has since been used to prevent muscle spasms and increase flexibility. You need a partner for these stretches.

Warming Up

Before engaging in PNF stretching, your legs must be limber. Run one quarter-mile at a jogging speed and one quarter-mile at half a sprint. Then rest for five to 10 minutes; this is your pre-exercise cool-down period. When you have caught your breath, stand up, bend down, touch your toes and hold the position for several seconds. Crawl both hands over to your left foot, hold, and then repeat on the right side of the body. You're now ready for PNF stretching to begin.

How It Works

Lie on the ground with your left leg straight up in the air, forming a 90-degree angle. Have your partner hold the heel of your shoe and try to push your leg forward with all of your might for five to six seconds. Your partner must push back against your foot, effectively creating resistance. Then have your partner push your foot forward while you push back with your leg. Repeat the exercise on each leg two to four times.

Other Rules for PNF Stretching

Because of the tremendous resistance placed on the hamstrings, specific rules are recommended. For instance, you should leave at least 48 hours between sets of stretching and do not use this stretch immediately before an athletic event. Additionally, leave at least 30 seconds of rest between sets so as not to overwhelm the muscle.

Cautions

The most important thing to remember about PNF stretching is that not one size fits all. The levels of contraction will vary with the individual's level of conditioning. So don't push your partner to accomplish more than they're ready for. In addition, if your hamstring has been injured you cannot apply the maximum contraction.