Located on the backs of your thighs, your hamstrings actually comprise three distinct muscles: the biceps femoris, the semitendinosus and the semimembranosus. Together, these muscles bend, or flex, your knees and extend your hip. You use these muscles anytime you move through space, whether it's by walking, running or jumping. In general, the hamstrings are tight, and this tightness can lead to pain in the knees and lower back. Dynamic stretches can help maintain or improve flexibility in this muscle group.
Exercise scientists have developed a system of categorizing stretches. Dynamic stretches, one of the major types of stretches, involve repeatedly moving a joint through its range of motion. This is in contrast to static stretches, in which you hold a position for an extended period of time.
You can dynamically stretch your hamstrings with a straight-leg march. In this stretch, you walk forward, extending your leg in front of you as you take a step. By increasing the height of your leg, you increase the stretch in your hamstrings. You can do basically the same movement without advancing forward in dynamic leg swings. For this stretch, you repeatedly swing your leg in front of and behind your body, like a pendulum. An alternative dynamic stretch for the hamstrings is the inchworm, where you place your hands and feet on the floor. Keeping your legs straight, you walk your feet toward your hands until you can no longer keep your legs straight. Then, walk your hands farther in front of your feet so you can repeat the process.
Because you rely on your own strength, not an outside force or prop, to produce the stretch, dynamic stretches are quite safe. These stretches can help with maintaining the mobility you need to accomplish movements necessary for daily living and sports. If the dynamic stretch mimics movements you use in your sporting activities, it can help improve your performance. As you perform dynamic stretches, your movements generate heat, which can make your muscles more elastic. Finally, dynamic stretches, when used as part of a warm-up, are more effective than static stretches at improving hamstring flexibility, according to a study published in the "Journal of Strength and Conditioning Research."
Dynamic stretches, because they generate heat and won't drain your hamstring strength, make ideal components of warm-ups. After doing a brief stint of cardio activity -- approximately five to 10 minutes -- choose one of the dynamic hamstring stretches. If you're doing the inchworm or straight-leg march, repeat the exercise until you've covered your desired distance, about 30 feet for the inchworm or 150 feet for the straight-leg march. If you're doing the leg swings, do between 10 and 12 swings with each leg. On the first repetitions, keep your leg low to the ground and increase the height as your muscles loosen up.
- Human Kinetics: Types of Stretches
- Journal of Strength and Conditioning Research: A Dynamic Warm-Up Model Increases Quadriceps Strength and Hamstring Flexibility
- Runner's World: Dynamic Stretching Better Before Training and Racing
- Essentials of Strength Training and Conditioning; Thomas R. Baechle and Roger W. Earle
- Dynamic Stretching: The Revolutionary New Warm-Up Method to Improve Power, Performance and Range of Motion; Mark Kovacs
- The Outdoor Athlete; Courtenay Schurman and Doug Schurman
- ExRx.net: Common Orthopedic Inflexibilities
- The Concise Book of Muscles, Revised Edition; Chris Jarmey