Most sports are quad-dominant. Leg exercises work the quadriceps, which become very powerful compared to their opposing muscle group—the hamstrings. The imbalance can lead to additional strain on the pelvis, causing a condition, fairly common among athletes, called anterior pelvic tilt (APT). It's a posture problem which, if uncorrected, can lead to decreased performance and pain in the lower back, hips and knees.
Signs of APT
The first sign of APT is usually tightness in the hamstring. Often this is near the top of the hamstring, but not always. The tightness can become painful if untreated due to slight tearing during training. It often restricts range of motion (ROM) when running, but it may not be immediately noticeable. It will be visible by an observer or on video as a shortening of front-side running mechanics—the thigh does not come up as high when you run at full speed.
To determine whether you have APT, find the peak of the hip/pelvis at the front and the same at the back and stand up straight. If you place a finger on each of these points, they should be roughly level. If the back is higher than the front, your pelvis has an anterior tilt.
SEE: Anterior Pelvic Tilt
Often, people incorrectly decide they need more flexibility in their hamstrings. After a period of rest, they focus on increasing their range of motion or flexibility of that muscle. If you have done this and it has had no effect, you are probably treating the symptom, not the cause.
Improvement in flexibility needs to come not from the hamstring, but from the quads and hip flexors. The best way to do this is to use proprioceptive neuromuscular facilitation (PNF) stretching.
Plyometrics can strengthen the hamstrings and improve balance between the quadriceps and the hamstrings. They also maintain the pelvis in a more neutral position, improving your posture. Learn more about proper posture.
Many injuries are caused by either weakness or imbalance. Weakness occurs when you constantly focus only on the muscles and tendons that directly contribute to your event, letting others atrophy. Imbalance occurs when muscles work in opposition to each other. If one side becomes overly developed, the opposing side will eventually get injured because of the imbalance.
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