Baseball players deal with a lot of different injuries over a long season filled with ups and downs. Most of the time, we focus nearly all of our energy on the elbow, shoulder and thoracic spine but a common and yet often overlooked injury is to the hamstring muscle group. Baseball is a sport that includes sporadic explosive sprinting and thus the hamstrings seem to be the “fall guy” most of the time.
Just a quick refresher, the hamstrings are a group of muscles made up four separate entities. The inner part of the thigh has two muscles that run from just below the knee to the bottom of the pelvis (1) semi-membranosus and (2) semi-tendinosus. On the outside of the thigh is the biceps femoris muscle which is divided into two separate parts, (3) the long head and (4) the short head.
Figure 1: (a) the hamstring muscle group from the rear view shows three distinct groups from left to right 1-long head of biceps femoris, 2-semitendinosus, and 3-semimembranosus. (b) from the side view the short head of the biceps femoris can be identified as it does not travel all the way up to the pelvis.
I had a coach once tell me that baseball was as simple as “you throw the ball, you catch the ball, you hit the ball and you RUN”. On second thought, that might have been Skip, manager of the Durham Bulls, in “Bull Durham” the movie. In any event, running is an integral part of baseball but is usually restricted to a quick dash down the baseline or a burst through the outfield grass to track a fly ball. When we consider normal sprinting, the hamstrings are the key muscle group that slows down the movement generated at the end range of every stride.
In the first photo Jacoby Ellsbury is pushing off his back foot while his front foot (in midair) prepares to make contact with the ground. For his foot to make contact with the ground, he needs to extend (or straighten) his knee and flex his hip quickly. In the second photo, Andrew McCutchen, who is just slightly ahead of Jacoby in the sprint cycle, has both feet off the ground and you can see his lead knee has already begun to extend. This motion happens at lightning quick speed during the sprinting cycle and if unopposed by the antagonist muscles, the knee would go past its natural anatomical range of motion. The hamstrings control (and inherently slow down) this movement and are under maximum stretch when they must perform this job. When a muscle is under the highest amount of stretch and then must perform an active contraction, there is the highest risk of strain.
Although we can’t change the explosive nature of the game, the real question is why are some people more susceptible to hamstring injury and what can we do about it? Risk factors and contributors to hamstring strain injury include all of following: (1) poor core stability, (2) decreased strength of hamstrings at longer lengths, (3) decreased flexibility of hamstrings, (4) neural tension, (5) tight hip flexors, and (6) weak and/or poorly active gluteus maximus. Each of these would, in fact, be future articles on their own so to explain all those factors in depth could turn this article into a book. So I’ll leave you with some real simple advice that you can take onto the field and incorporate with your fall ball programs today.
Firstly, a proper warm-up is paramount! We need to prepare our bodies for the demands that we intend to place upon them in practices and games. This means that progressive sprints must be involved in a baseball warm-up and should be performed throughout a game between innings. Just because you did your sprints before batting practice that day doesn’t mean that your body is still ready to track that ball into the right field corner in the 7th inning. With that said, make sure players are staying warm throughout a game and it’s never wrong to break up a few drills at practice with some ¾ speed sprints.
Secondly, we look at hamstring flexibility. I think that everyone and their dog will admit that they have tight hamstrings or aren’t as flexible as they would like to be. It’s simple, if the muscle is tight then you are more likely to strain it in its lengthened position when you need it to activate. Performing static stretches of your hamstrings will increase their flexibility but it may not even be the hamstrings that need stretching. The concept of neural tension is a tough one to conceptualize but when carefully considered it may be simpler then you think. The nervous system consists of the brain, spinal cord and all the nerves that run to muscles. All of these structures are connected and continuous with each other. Just as when we move our legs we stretch our muscles, we can also stretch the nerves that run from our spinal cords and to the muscles that they activate. Some recent research (Gibbs, Cross, Cameron & Houang, 2004) has suggested that nearly half of all hamstring injuries don’t present with any structural muscle damage on MRI. Some researchers suggest that the true value may be closer 1/3 of hamstring injuries but nonetheless why the pain? As mentioned before, the nervous system may be inflexible as well. The nerves need to glide and slide between tissues in our body as we produce movement and there are areas where they run the risk of being pinched or stretched. Now stretching a nerve could definitely cause considerable discomfort so it would be naïve to think that this can’t cause the symptoms in the back of the thigh in some cases. Regardless of the mechanism of this loss of flexibility, there is a simple exercise (pictured below) that can be added to a players routine to address both of these issues.
The standing ball roll out exercise will help to stretch the hamstrings in the start position or mobilize the nerve tissue as it is done dynamically and does not include a static hold. As a prescription, we would typically do this exercise 15-20 times and complete 3 sets of this on a daily basis. The back must remain in an upright position at all times and balance will be challenged somewhat which is never a bad thing.
While we’re at it lets make sure to stretch the hip flexor as well. The picture below shows a stretch of the hip flexor that we commonly see on the field and I definitely think it should be included because when the hip flexor is tight the pelvis can tend to be rotated forward.
When the pelvis is rotated forward the hamstrings are put onto a “pre-stretch” as we call it. Since the hamstrings originate from the bottom of the pelvis, any rotation moves this bony attachment up and away from its anatomical position. In this position, the hamstrings are already beginning to become stretched and at a disadvantage before we even begin any movement.
So for now we have at least three things to consider when protecting ball players from hamstring injuries. (1) warm-up properly and stay loose, (2) get the tissues on the back of the thigh moving and (3) stretch those hip flexors!
As usual, if you have a player with a recurrent hamstring injury or a “twinge” that just won’t go away then get your player in to see a physical therapist or health care professional as soon as possible. It is likely that with early risk factor identification and mitigation hamstring injuries can be avoided. These types of injuries can be debilitating in nature and a cause for prolonged and recurrent stints on the DL. By taking an active role in prevention and being an advocate for players, coaches can help direct players to get the help they need and thus reduce time spent recovering from injury. At the end of the day, development of players happens on the field so we should take the steps to ensure they remain out there as much as possible.