Protecting Your Hamstrings

Hamstring injuries are one of the most frequent injuries seen in sports. Hamstring injuries often occur at the biceps femoris muscle of the hamstring between the late swing phase and early stance phase of the sprint.

Biceps Femoris Muscle

What could put an athlete at greater risk of hamstring injury? Here are a few factors:

bad sprinting mechanics
previous hamstring strain injuries
lower limb muscular imbalance

A recent study has found there are two other factors that may indicate the most significant link to hamstring injury risk. These are hamstring muscle fascicle length and eccentric hamstring strength. A muscle fascicle is a collection of muscle fibers wrapped within connective tissues. Muscle fascicles can vary in their length. An eccentric hamstring contraction is a contraction where the hamstring is lengthening while the muscle is contracting to resist the lengthening. This study produced a four-quadrant graph that depicted the muscle fascicle length and eccentric hamstring strength test results of 152 Australian soccer players. These results found that those with short biceps femoris muscle fascicles and poor eccentric hamstring strength were far more likely to experience hamstring injury. The least likely to experience hamstring injury were those who had good eccentric hamstring strength(above 337 N) and long biceps femoris fascicle lengths (above 10.56 cm). The stronger and longer(in fascicle length) their hamstrings were, the less likely they were to be injured.

This graph was interpreted from this study.

Eccentric exercises train the lengthening portion of a contraction. This is done by contracting a muscle while it is lengthening under a load, resisting the lengthening of the muscle. One example of this would be controlling the descent of a dumbbell by contracting the bicep after a bicep curl. This is a slow eccentric contraction, more capable of building strength. Another example would be the initial contraction at each ground contact during a sprint before pushing to the next leg cycle. This is a rapid eccentric contraction, more capable of lengthening the hamstring muscle fascicles. By eccentrically training the hamstrings, your muscle fascicles will be lengthened and your hamstring will be strengthened.

The most vulnerable hamstring is an untrained one. An athlete's goal should be to get their hamstrings strong (eccentrically) and long (in fascicle length). How can athletes go about doing that?

Nordic Hamstring Curl

For some time, this exercise has been known as one of the best ways to train the hamstrings eccentrically. Many studies have been conducted that directly link the nordic hamstring curl to reducing hamstring injury prevalence. One study found that the inclusion of this exercise reduced injury prevalence in soccer players by 51% by improving eccentric hamstring strength and hamstring muscle fascicle length.

The nordic hamstring curl only requires having something (or someone) that can hold you down and support your weight.

To perform this exercise:

lock your feet in place and maintain a 90-degree angle at your knee.
while keeping an upright posture above the knee, slowly lean forward
whilst going down, resist the momentum by eccentrically contracting the hamstring
catch yourself at the bottom of the repetition if needed and reset to the starting position

Romanian Deadlift

This exercise allows you to eccentrically strengthen the hamstrings at different speeds, long lengths, and even unilaterally. It is a hinge movement and can be done with a barbell, dumbells, kettlebells, or your bodyweight. This exercise can be progressed by increasing the weight, doing the workout with a single leg at a time, or by letting the weight fall quickly and catching it inducing a supramaximal eccentric contraction at the bottom of the lift.

To perform the standard barbell Romanian deadlift:

start in an upright standing position holding the barbell in front of you.
push your hips back and lean forward, this should positively change your knee's angle.
continue to do this until your hips can't go further back.
lift the weight back up by extending your hips and returning to an upright body position.

Eccentric Hamstring Curl

This exercise can be performed by using slide boards on the ground, a Bosu ball, or whilst wearing your socks on a hardwood surface at home. This exercise can be progressed by adding weight, increasing the speed of contraction, or performing it with a single leg solely during the eccentric phase or during the eccentric and concentric phase.

via youtube

To perform this exercise:

start on your back with your hips risen in the air and your feet nearly below your knees.
push your feet away from you to lengthen your hamstring with a controlled contraction until your knees are in full extension without allowing your butt to touch the ground.
pull your feet back towards you while still keeping your hips off the ground to return to the starting position.
this exercise can be performed "eccentric-only" by lowering your hips to the ground after extension to rest your hamstrings and avoid a concentric contraction when pulling your feet back in.

If You Sprint In Competition, Sprint in Training Too

If you sprint in your sport then sprinting in training will generate adaptations that will protect your hamstrings during competition and improve your sprint.

A recent study observed that a sprint training regimen provided benefits to hamstring muscle fascicle length and thickness, and also led to an improved 10m sprint time. Improvements in biceps femoris fascicle length and sprint performance were greater in the sprint training group versus the Nordic hamstring training group in this study.

When sprinting during competition, an athlete must adjust their technique to deal with other factors such as opponents, teammates, fatigue, or carrying a ball or stick. It can be very difficult to maintain good running mechanics while also having to adapt to these outside variables in competition. This puts an athlete at greater risk of faulty movement mechanics that can ultimately cause a hamstring injury. By maximally sprinting at controlled distances in training, athletes will expose themselves to their top speeds while having a greater focus on applying optimal sprint techniques. Sprinting in training sets an athlete up for sprinting in the game.

Some hamstring injuries just occur from bad running mechanics that could come from a slew of factors like those mentioned above. Don't wait until the game to run at your fastest speed. With the right programming, sprinting during training might actually save you from a hamstring injury rather than cause it.

Don't Stop The Eccentrics

Athletes become the most at-risk for hamstring injury when they don't consistently train the hamstrings eccentrically, leading to shorter hamstring muscle fascicles and weaker hamstrings. It is common practice for athletes to stop weight training when their competitive season starts but this does not mean it is a good practice. This study found that teams who use strength training programs during the season suffer significantly fewer injuries than teams who do not. Training the hamstrings eccentrically at least once a week can keep your hamstrings strong and long. If you stop training the hamstrings eccentrically for just two weeks, muscle fascicle lengths start to drop. After a few more weeks (3 - 6 weeks), hamstring muscle fascicle lengths drop back down to pretraining levels (study).

Eccentric hamstring training should be included in your training regimen at least once a week. This study found that only 2 sets of 4 repetitions of Nordic hamstring curls per week improved or maintained hamstring muscle fascicle length for 6 weeks. Whether through Nordics, RDLs, sprinting, or some other eccentric hamstring exercise: hamstring muscle fascicle length and strength must be maintained, otherwise, it will be lost.

09-14-2022

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