INTRODUCTION
It was sad to see Adam Gemili pull up with a hamstring strain during his 200m heat on Tuesday and I have no doubt his injury brought back horrible memories for many others. Hamstring injuries are all too common. In sports that involve high volumes and/or intensities of running such as football, rugby and AFL they cause a huge injury burden. On average European football clubs suffer 5-6 hamstring injuries a season and incidence is increasing.
WHAT IS THE MECHANISM?
Let’s start by explaining the anatomy of the hamstrings group and how they function. They are made up of 3 muscles which are biarticular; they have attachment sites across both the hip and knee joint. They contribute towards extension at the hip and knee flexion. Along with the glutes, the hamstrings have huge force generating capabilities during hip extension which contributes to faster running speeds. It’s other function during running is to stabilize when the foot hits the ground and prevent further extension at the knee. This may seem like a minor function but when we sprint the forces are huge and the hamstring has to work eccentrically to brake. These types of muscle contractions are more fatiguing and tend to cause more muscle soreness over the following days.
What is the most common mechanism for a hamstring injury? The majority of these injuries occur during sprinting, more specifically during the terminal swing phase of the running gait (See picture). You will notice that in this position the hip is flexed and knee extended. This actually looks like a position you would get into to stretch your hamstrings. Consequently, your hamstrings have to produce a huge amount of force in a really stretched and long position, hopefully its quite clear to see why this leaves them very vulnerable! This is a very important point to consider when we prescribe exercises to improve hamstring strength.
As with any injury, some risk factors are modifiable whilst others are not. Age and previous injury history are non-modifiable. If you are over the age of 28 and have had hamstring injuries in the past your risk will be higher than your injury free, younger team mates. However, research has shown risk can be significantly reduced with appropriate interventions. Eccentric hamstring strength, increased muscle fascicle length, reduced asymmetries across limbs, consistent exposure to sprinting and high speed running and good lumbo-pelvic control are all modifiable risk factors and have been associated with decreased risk of injury. In this article we will explore some of the ways you can improve these qualities within your training.
EXERCISES TO REDUCE INJURY RISK
Exercises are split into 5 categories:
1. Knee Dominant: The hamstrings have an attachment across the knee joint and contribute towards knee flexion. However in the context of sprinting they contract eccentrically to prevent excessive knee extension, therefore our exercise selection reflects these.
2. Hip Dominant: The hamstrings are involved in hip extension which is vitally important for generating force to sprint quickly. We also know hip dominant exercises tend to require greater activation from the lateral hamstring which includes the bicep femoris long head (BFlh). Research has show that this is the most common site of injury (88%).
3. Rate of Force Development: Sprinting is fast! An element of our training needs to reflect that, and the best possible training tool we have is sprinting. With previous exercise types we are training the muscle to produce more force. With this category we are training the muscle to produce this force quicker. In the context of sprinting, the movement durations are extremely quick so the muscle needs to be able to produce force at extremely quick rates.
4. Isometrics: This refers to exercises where muscle length stays constant. These exercises reflect the body position during the terminal swing phase of running so help with neuromuscular control and transfer to running performance. The catches are an attempt to overload this movement and challenge stability
5. Perturbation: We like to include these exercises because they challenge the stability component. Sprinting rarely occurs in a nice stable, linear fashion, it often involves body contact with an opponent, slight changes in direction or instable surfaces.
KNEE DOMINANT
If I could pick just 1 exercise for you to take away with you today it would be the Nordic Hamstring Exercise. We term this knee dominant because the hip remains extended and fixed throughout, whilst the knee gradually moves from a flexed position to full extension. When performed correctly this exercise has been shown to significantly improve eccentric hamstring strength and increase fascicle length both of which reduce the risk of hamstring injury. When I talk about 'long' hamstrings, fascicle length is what I am referring to. This doesn't have anything to do with flexibility this is to do with the length of the muscle fibers within the muscle and can only really be assessed with ultrasound or MRI. Although difficult to measure we can be confident that these heavy eccentric exercises are very effective at increasing fascicle length.
If you struggle to maintain control throughout the movement start with the modified Nordic in the video below. As this becomes more comfortable remove a band and hold one behind your back. Continue to progress until you can get nose to floor without any support from a band. Once you can achieve this for 2 sets of 4, begin to increase difficulty by holding a weight, increasing in 5kg increments. An important factor here is consistency. Detraining can occur in just 14 days.
HIP DOMINANT
Romanian deadlift (RDL) variations are my go to in this category because research has shown they require a large amount of effort from the BFlh. There are a number of different variations. Start with the bilateral RDL and make sure you learn how to hinge correctly. This is a vital movement competency and something we work on with all our athletes. An incorrect hinge pattern will lead to inefficient loading patterns and could cause lower back pain.
Once you've mastered this movement don't be afraid to load it. I like to progress to a single leg RDL because it adds a stability component and it better reflects the running action. Ground contact occurs on one leg. Once you've mastered the technique of a single leg RDL we need to remember for an exercise to be truly eccentric it needs to be heavy! For this I love the 2:1 version: pick the weight up with 2 legs, lower with 1. This will allow you to load the exercise up in a safe way and get better adaptations.
RATE OF FORCE DEVELOPMENT
As mentioned earlier the majority of hamstring injuries occur when sprinting, this means high forces are being produced and at extremely quick rates. By far the best way to protect against hamstring injuries and develop rate of force development (RFD) is to sprint regularly. As with most things, we get better by practicing the task at hand, and sprinting is no different. It is paramount that you sprint as fast as you can every week and keep volume and effort distances appropriate for your sport. If you play full back in football your effort distances could reach 50-60m and your total volume is high. But if you play Centre back your effort distances and volume will be much shorter. With our athletes we will use competition and real time feedback with timing gates to ensure they hit greater than 90% peak speed every week. In addition, athletes will look to achieve approximately double there match day sprint distance in training. The key here is to build this up gently, the enemy is large fluctuations in load. When it comes to sprinting we want to build up the amount you do over a number of weeks and then maintain.
However there are some great exercises you can do in the gym: the kettlebell (KB) swing is a great exercise for developing RFD of the hip extensors, both glutes and hamstrings. I like the banded variation as it adds another dimension to the exercise. You have to produce more force to move it quickly but you are also required to brake and slow the KB down quicker, both beneficial traits. Sam discusses this more over on our YouTube channel. I also like the banded RDL. During this movement you let the band pull you to the floor before hitting the brakes hard and fast during the final stages. Again this mimics the action of the hamstring at terminal swing phase, our vulnerable athletic position.
ISOMETRICS
These exercises could be the missing piece of the puzzle. Hamstring bridge switch challenge the isometric component of running. Start with a very simple long lever hamstring bridge, and switch slowly. By elevating the shoulders and feet it challenges your ability to maintain hip extension. As you get more comfortable begin to switch more aggressively. Eventually you can add weight across the hips.
PERTUBATION
I really like the slide board variations here with a long lever. Keep hips elevated and aggressively slide feet as fast as possible for 15-20s.
I also like an adaptation on the hamstring bridge switches we utilized previously, by aggressively moving the weight we need to co-contract through the hip extensors and maintain stiffness throughout the body. Although less rigorously studied as the previous exercises these are great for challenging neuromuscular control and building some muscular endurance in those vulnerable positions.
CONCLUSION
I have to be honest, these exercises will not remove all risk of injury, and anyone that promises their program can isn't telling the truth. However, there is strong evidence to suggest they go a long way in reducing risk especially if you are someone who has suffered a hamstring injury previously. There are other components we can address too such as pelvic control and I encourage you to check out our FREE 12 week functional core program for more information. If you found this article useful please share on social media, and if you give some of these exercises a go, tag us in them we would love to see you getting involved. @myperform_ssc @jackchristopher_perform @perform_coach_sam