Hamstring injuries are very common in baseball. What causes these injuries? Most seem to occur while runnning but it is not uncommon to learn of a player pulling a hamstring while swinging a bat or bending over to get to a ball.
If you read enough articles on this topic, invariably you will be told that stretching the muscle beyond its limit can strain or tear the hamstring or cause sharp pains, spasms, swelling and bruising. If it hurts to run or if your hamstring is bruised and tender, the diagnosis is overtraining, muscle tightness and fatigue.
You may also read that inflexible hamstrings limit motion and stress the lower back. If you have knee pain, it may be due to hamstring tightness (or weakness) because the knee has to work harder to perform extension movements. You may also read just the opposite, that tighter hamstrings are less susceptible to injury and allow you to perform better!
If these symptoms were indicative of the true causes of injury and if everyone followed the recommendations for fixing them, (that typically include more stretching and strengthening), the number of hamstring injuries should decrease greatly. But we do not see this. Instead, we still see many injuries occurring, and, in some cases, more severe than usual. It is rare to find a team with no hamstring problems! Many teams, including professional ball clubs, have even lost great players for most of, if not the entire, season because of hamstring injuries as for example, Ken Griffey, Jr., and Jose Reyes of the Mets. If you check the injury lists on the professional level you will most often find at least one player out with a hamstring injury.
What is missing in these diagnoses and fixes, is understanding how the hamstrings function in running and other sports. For example, when you drive the knee forward, the hamstring undergoes an eccentric stretch at the hip joint and when the shin whips out, there is a stronger eccentric contraction of the hamstring muscle and its tendons at the knee and hip joints. These eccentric contractions are needed to prepare the hamstrings for the pawback movement, the main force-producing action to drive the leg down and back to make contact with the ground and propel the body forward.
But what happens to the eccentric-concentric contractions at the hip joint and knee joint if the switching of the contractions misfire or the player has incorrect running technique? This has not been looked at by the teams mainly because they do not have any personnel qualified to do this. In doing biomechanical analyses and working with hundreds of runners from the beginning level to the professional ranks, I have come to the conclusion that it is the synchronization of the contractions and joint actions that cause hamstring injuries due mainly to improper technique.
Constantly stretching the hamstrings does very little to prevent injury, and may even be a contributing factor to injury. When you drive the thigh forward, the knee is bent which gives slack at the hip end of the muscle so that you have an ample range of motion. Overstretching creates conditions that do not allow the hamstring to function properly.
In regard to tight hamstrings causing back problems, I have yet to see a player who has such tight hamstrings that he does not have normal curvature of the spine. In other words, if the spine is held in its normal anatomical position while running, the hamstrings cannot be considered too tight to cause the back to flatten.
Any back flattening that occurs should be when the body is in full support on the ground at which time the hamstring at the hip joint is stretching (hip flexion) and thus, cannot be “too tight.” If you can do a half to three-quarter squat while maintaining normal spinal curvature, you do not have excessively tight hamstrings.
Constantly stretching the hamstrings as many players do, is I believe, often the cause of many running injuries, especially to the hamstring. Many players are proud of the fact that they can touch their toes when they bend over with straight legs or can raise their leg up onto a rail and then bend over and touch the foot with the fingers.
However, In most of these exercises, because you have a rounded back, you overstretch the ligaments of the lumbar spine more than you stretch the hamstring. As a result, you end up with a looser back more prone to injury rather than a safer or stronger back or hamstring muscle.
Muscles need strength with flexibility, thus, instead of doing mainly stretches, you should do strength exercises that also stretch the muscles and connective tissue in the same exercise. For example, doing the squat exercise stretches the quadriceps and hamstrings eccentrically at the hip joint on the down phase, if you maintain normal curvature of the spine.
When you rise up, you strengthen these muscles in the concentric contraction. Thus, you stretch and strengthen in the same exercise. For baseball players, you do not have to go through a greater range of motion for more stretching because it is never encountered in running.
But if more is needed for other skills, the payers should do exercises such as the good morning, hip extensions on a Glute Ham machine and the glute-ham-gastroc raise on the Yessis Glute Ham Back machine. This latter exercise is the only one that strengthens the hamstings at the hip and knee joints in sequence. Athletes who do this exercise and who have good running form, have not had, nor do they get, any hamstring problems.