Facts Needed to Prevent Hamstring Strains

Once you've experienced a hamstring strain, you wish nothing more than for it to never have happened or at least for it to never happen again. The sad truth behind this desire is that once you’ve strained it once, it has an increased risk of reoccurring. This is especially true if you're performing any activity that requires hip flexion combined with knee extension such as sprinting. If you're doing sprints in your program, this can be a very dangerous set up if you have a history of hamstring strains. Once you've pulled a hamstring, you have a risk of injuring it again for up to a year after the first injury. The long recovery period is partially the reason why the recurrent rate of injury is so high. It's important to understand what happens anatomically when a hamstring is strained and learn the most effective way of treating and preventing the injury to limit future strains.

Risk factors and injury process

Hamstring strains can be the product of a culmination of issues in the leg. There is evidence that any previous injury to the hamstring, older age, and limited quadriceps flexibility can all have a role in future hamstring strains (4, 5). Limited quadriceps flexibility when assessed with a Thomas test had a higher incidence of hamstring pulls (4). Surprisingly, hamstring flexibility wasn't one of the factors that accounted for hamstring pulls. It also displayed a link in the muscular imbalance between the quads and hamstrings as a leading factor at play with strains (2). The overpowered quadriceps increase forcible extension speed of the leg, which can cause overpulling of the hamstrings, especially when movements powerful by nature are performed.

When looking into other factors that perpetuate the problem, some studies found that when an athlete is older in the sport, there is a greater incident of strains (4). This can be linked simply to the fact that there is more time for an injury to occur in the athlete's playing or lifting career when compared to the younger athlete. Age alone isn't a determining factor in the event of a hamstring pull. The greatest disposition for a future hamstring strain is most related to a previous strain. But what causes the strain in the first place?

The injury process for a strained muscle starts where the swing of the leg ends. When the leg is fully extended out (like a kick) and absorbing the force from the swing of the leg, the hamstrings are eccentrically contracting. Lengthening the muscle (specifically the biceps femoris) under force leads to the excessive pulling on the muscle and can cause strains. Most of these strains happen at the point where your tendon transitions into the actual muscle belly (3). When it is pulled, inflammation immediately goes to the area of injury to prevent further damage and to begin the healing process. Once damage has occurred to the muscle, MRIs have shown that scar tissue can persist on it for 12–23 months (10). The scar tissue limits the length that the hamstrings can contract. This is part of the reason why previous injury to the area primes it to be injured again. Considering that hamstrings are so susceptible to further injury, a practical and pointed rehabilitation approach to the area is vital for getting back in the game injury-free.

Preventing future strains

In efforts to prevent future strains on an injured leg, the quickest way to solve the problem is to get to the source of the issue. Strains occur when the muscles of the hamstrings are forcefully eccentrically contracted. Outside of tissue healing with TENS units, ultrasound, and massage, the first step of rehabilitation should be training eccentric contraction of the hamstrings. Exercises such as box depth drops both loaded and unloaded, sled dragging backward, and single leg Romanian deadlifts are great at accomplishing this task (9). Moving up the kinetic chain is step two of the rehabilitation process. The hips have a huge role on overall hamstring length. If they are out of alignment (e.g. anteriorly tilted), the hamstrings' functional length is decreased. Working to reestablish normal hip position helps prevent future strains. Exercises such as half kneeling chops, rotating core planks, bowler’s squats, and hip neutral ball leg curls are all effective at accomplishing hip alignment (9). Studies have shown that when specific core stabilization exercises (such as those listed) were performed with focus on proper hip alignment, there was a 70 percent decrease in a consecutive injury of the hamstring when compared to a group that didn't focus on hip alignment and strength as a rehabilitation technique (8). This result was seen after one year from returning to sport. Hip strengthening and proper alignment have produced impressive results in limiting the risk of consecutive injuries.

Correcting muscular strength is only a piece of the puzzle. Controlling how the muscles move can prevent hamstring strains as well. While it's important to correct the muscular length and strength of the hamstring, the overall control of the leg and how it reacts can be factors that need attention as well. It has been shown that having underdeveloped neuromuscular control of the leg can be just as risky in causing strains (1). Rehabilitation techniques that work on correcting the movement pattern of the leg show promise in limiting future hamstring pulls. When the leg has excessive movement outside the normal plane of motion when sprinting, the neuromuscular system is unfamiliar with having the muscles in certain positions and a strain can occur. In these unfamiliar positions, muscles aren't used to contracting in a specific fashion, and weakness in synergist muscles creates a situation that can overstretch the hamstring and lead to injury.

Vern Gambetta and Benton have advocated a dynamic multidirectional warm up for years (6). This won't only prime the body for the workout, but when agility and dynamic stretches are performed correctly, it trains the neuromuscular system to fire correctly in unfamiliar positions. Ultimately, this can reduce the amount of strains that can occur over a season or even a lifetime. The proprioceptive and neuromuscular firing improvements from the use of dynamic warm ups displayed a 36 percent decrease in the rate of hamstring strains in a group of female soccer players over a three-year span (7). These are extremely positive results from just adding in a dynamic warm up. It should be an easy addition to any program to help rehabilitate and prevent strains. Using a well-rounded approach to combating the issue of another injury to the hamstring is the best way to make sure that you tackle the issue from all limiting factors that can cause the problem.

Summary

Hamstring strains can be a very prolonged injury. Once you experience a strain, the risk of injuring the hamstring again is always looming in the future. It can be a challenge to return to the field or weight room with full confidence in your lower half. Though it will take time for the healing process to fully complete the cycle, the use of specific preventative measures can get you back in the game. Focus on strengthening the muscles. In addition, extended proper hip alignment and neuromuscular control of the leg attack the problems directly at the source of injury. Specifically, this is accomplished with eccentric hamstring exercises, hip stabilization exercises, and dynamic warm ups. These are the tools for a successful rehabilitation process that will retard any future strains. Take time to throw these few things into your training program and they can keep you on the field or in the gym. Limiting your time lost will always be the best method for moving forward. Goals are never achieved from the sidelines.

Sources

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