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Hamstring Injury – Part 2

Hamstring Injuries Part 2 – How to strengthen your hamstrings  

Author: Leo Bell (Physical Performance Coach)

In part 1 of this series we discussed the risk factors that increase the likelihood of sustaining a hamstring strain injury. In a short review, we highlighted hamstrings that have short fascicle length, poor eccentric strength, and unaccustomed to high intensity efforts (such as sprinting) are more vulnerable to experiencing a strain injury.

Therefore, our aim as physical performance coaches is to create adaptations that make our athlete’s hamstrings longer, stronger and conditioned for performance. Fortunately, research has indicated that exercise interventions and training load modifications are an effective way to reduce these risks and prevent hamstring strain injuries.

Medial, Lateral, Proximal, or Distal?

What’s more to consider before prescribing hamstring exercises, is to understand the anatomical function of the hamstring group. The hamstring group is responsible for hip extension and knee flexion moments, with the exception of the bicep femoris short head, which only crosses the knee joint. This makes the hamstrings predominantly important during locomotive actions such as propelling us forward during walking, running and sprinting. And also important in the deceleration of the lower leg during the terminal swing phase of running.

The hamstring group can be divided into medial and lateral hamstrings, namely the semimembranosus and semitendinosus (medial), and the biceps femoris long head and short head (lateral). The medial hamstrings originate at the ischial tuberosity and insert just below the knee joint at the medial aspect of the tibia. The bicep femoris long head also originates at the ischial tuberosity, but it inserts laterally on the head of the fibula. The short head originates on the linea aspera and lateral supracondylar line of the femur, and inserts at the lateral aspect on the head of the fibula. Due to its line of force, the medial hamstrings can be biased by slightly internally rotating the leg and foot during knee flexion, and vice versa for the lateral hamstrings. Understanding these origins and insertions allows us to bias muscles during exercises for a targeted approach.

hamstring muscles

Moreover, research using functional magnetic resonance imaging (fMRI) and surface electromyography (sEMG) has allowed an insight to the metabolic and electrical activity of each muscle during different posterior chain exercises. Knee-dominant hamstring exercises such as the Nordic or hamstring curl tend to favour the Biceps femoris short-head and semitendinosus muscles. Whilst hip-dominant exercises such as 45-degree extension and Romanian-deadlift tend to target semimembranosus and bicep femoris long-head muscles. This knowledge is key in providing a general injury prevention program to ensure you are hitting all the key muscles and not leaving any underdeveloped. Moreover, it is important to know when treating a problem area for an individual, and ensuring that the right muscle is receiving the appropriate stimulus.

hamstring injury

Eccentric Versus Isometric

There has been plenty of debate regarding whether an eccentric or isometric action occurs during high speed running. Which has flowed on to debate whether eccentric or isometric focussed exercises are more specific and effective. Without delving in and opening a can of worms, it is my opinion that both types of muscle contractions are important to train and thus should be included. There is strong evidence to suggest that improving peak eccentric force of the hamstrings during a Nordic exercise will reduce the risk of a strain injury. During a Nordic, a supramaximal eccentric contraction occurs in the hamstrings. The adaptations from this exercise cause the hamstring fascicles to lengthen, and increase the maximal eccentric strength. The only concern with this particular mode of contraction is that eccentrics promote exercise-induced muscle damage, which may result in an increased level of perceived muscle soreness. This can be difficult to implement during the middle of a competitive season as athletes want to remain ready and operational. However, repeated bouts of eccentric exercise over the course of 1-2 weeks reduces perceived soreness as we become more physiologically accustomed to the stimulus. Therefore it is important when including an eccentric focused exercise to maintain its use consistently throughout the competition period.

Alternatively, Van Hooren and Bosch (2017) have argued that there is no active muscle lengthening (eccentric) contraction during high speed running, and that an isometric contraction is apparent before the point of ground contact. Therefore in respect to this argument, including an isometric stimulus is also important from a behavioural context. This can be further discussed at a later date.

 

Bullet proof hamstrings

The following are 5 exercises that we use to develop robust hamstrings for athletic performance:

1 – Nordics

  • Ankles fixed, knees bent and hips extended
  • Hands at chest in a push up position
  • Maintain a neutral spine and avoid rib flaring or lower back arching.
  • Slowly extend at the knee, and allow the hamstrings to suspend you down to the floor
  • 2 sets of 4 repetitions
  • Progression: weighted Nordic lowers (e.g. hold onto 2-5kg during lower)

hamstring injury

2 – Romanian Deadlifts (RDL)

  • Hip-hinge pattern
  • Maintain a neutral spine as hips ‘slide back and forth’
  • Allow hamstrings to suspend the trunk into a lowered position until parallel with the floor
  • Keep weight close and slide down front of thighs to reduce strain on lower back
  • ‘Claw’ through the floor and stand up straight
  • 3-4 sets of 5-8 repetitions
  • Progression: single-leg RDL

hamstring injury

3 – Glute-Ham Raise

  • Hip-hinge pattern
  • Can be used for isometric holds or eccentric focus
  • Maintain a neutral spine and avoid rib flaring or lower back arching
  • Dig in through heels and slowly lower trunk towards floor
  • 3 sets of 4-8 repetitions
  • Progression: weighted lowers, isometric holds or catch

hamstring injury

4 – Single Leg Hamstring Bridge

  • Useful exercise for improving posterior chain strength-endurance.
  • Unilateral push
  • Concentric and isometric focussed
  • Tilt pelvis posteriorly (point belt-buckle up)
  • Push through heels
  • Hips up high as possible
  • 3 sets of 8-20 repetitions, with 2 second hold

hamstring injury

5 – Sprinting

Consistent exposures to high-speed running stimulus are important to maintain a velocity-based conditioning of the hamstrings. Previous research has suggested spikes in high-speed running loads precedes hamstring strain injury, as the hamstrings are not accustomed to the intensity of the exercise and result in fatigue and muscle damage. As the saying goes ‘there’s no fitness, like match fitness’. Therefore including a weekly high-speed stimulus to ensure your hamstrings are experiencing a maximal velocity contraction may have a prophylactic effect.

  • Ensure you are warmed up and prepared for a near-maximal effort
  • 4 x flying starts
  • g. Accelerate 30m, hold top speed 10m, Decelerate 30m
  • The emphasis is on what happens during the middle segment, and less effort should occur during acceleration and deceleration, hence the longer segments during those phases

hamstring injury

Summary

The hamstrings have an important role in running-based sports. Practitioners and athletes should be careful with exercise selection so they are not overloading or under-loading particular structures. This includes the volume, intensity and timing of the stimulus. Athletes should seek an individualised approach, particularly those with an injury history to ensure all factors are accounted for and they are working towards the best possible outcome.

 

Part 3 will be released soon where we will be looking at the rehabilitation of a strained hamstring

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Hamstring Injury – Part 1

Author: Leo Bell (Physical Performance Coach)

Hamstring strains are one of the most common sports injuries, with lots of time and money lost in the wake of a hamstring strain incident. The AFL have seen over 65 hamstring strain injuries (as of Round 11) so far in 2018, and you could only expect this tally to increase as the season progresses.

The pinch of hamstring strains has also been felt at local level sport, but recreational participants are at a greater disadvantage without the resources and treatment that a professional athlete may receive. Therefore, the reason for this blog is to discuss hamstring strain injury mechanisms, risks, and potential preventative strategies that we can employ to reduce their occurrence.

Whats the cause of a Hamstring strain?

A hamstring strain is caused as a result of a rapid eccentric (lengthening) contraction that exceeds the strain capacity of the muscle, resulting in damage to the muscle and/or neurovascular tissues (think of an elastic band stretching too far that it causes a tear in the band). This typically occurs during high speed running at the terminal swing phase, where the hamstrings are stretched over the hip and knee joints. Additionally, it is not unusual to see a hamstring strain occur during kicking or quick changes of direction. Whilst these movements are the mechanism of injury, they’re unavoidable. Additionally, risk factors predispose certain people to an increased chance of incurring a hamstring strain. So let us look at the risks…

hamstring strain

Risk Factors

There are two types of risk factors that we should concern ourselves with when discussing hamstring strain injuries – non-modifiable, and modifiable risk factors.

Non-modifiable risk factors – are those that are inherently beyond our control. The athletes age, race, muscle fibre type and injury history are examples of non-modifiable risks that increase the chances of experiencing a hamstring strain injury. Athletes aged older than 25 years are seemingly more at risk of injury. There are several theories as to why the age-related difference in hamstring injury risk exists, however none have been substantiated by clinical research. It is suggested that a loss of muscle flexibility and mobility of the lumbo-pelvic-hip complex is problematic for the length-tension relationship and ultimately exposes the hamstrings to greater strain. Moreover, research has indicated that athletes of African or Aboriginal descent also experience hamstring strains more often than Caucasians. The reason for this can be simply explained by their predominant muscle fibre type, as type 2 muscle fibres are more prone to strain than type 1 muscle fibres, due to their greater rate of force production and fatigue-ability. Whilst we know there is nothing we can do to change these risk factors, greater emphasis can be placed on negating the modifiable-risk factors and implementing preventative strategies.

Modifiable risk factors – are those that we can effectively change. Modifiable risk factors include muscle temperature, shortened optimal muscle length, reduced muscle strength and flexibility, and training-load factors such as speed exposures and fatigue. Due to early observations of hamstring strains occurring early in training and competition, it was declared that muscles were not in a prepared state for physical activity. Hence, the introduction of a well-structured warm-up was used to increase muscle temperature and improve the muscles pliability under stress. In addition to cold muscles, short muscle-fascicle length demonstrably increases the risk of future hamstring-strain injuries. If you can imagine, your muscle fascicles are made of up tiny cross-bridges that clasp onto each other and shorten during contraction. If these cross-bridges are clasped too tightly and the fascicle length is chronically shortened, there is a reduced capacity to stretch and therefore the yield point of the strain will be much sooner (resulting in a tear). Furthermore, shorter muscle-fascicles result in a sub-optimal length-tension relationship, effectively reducing the strength capabilities of the muscle and its capacity to withstand forces during running or kicking. Simply put, short and weak hamstrings significantly increase the risk of hamstring strain injury.

hamstring injury

With the development of GPS technology and research monitoring the physical demands of training and competition, we now know that a well-balanced approach to training is important to mitigate injury risk. Athletes are at a greater danger of hamstring strain injury due to the significant forces endured during high intensity efforts such as accelerations, decelerations and sprinting. The greater the forces produced during these activities, the greater the energy demands are on the hamstrings. The fatigue and muscle-damage induced by these high intensity efforts add to the danger of a hamstring strain. Because the muscle is fatigued, it loses the capacity to contract in a coordinated and timely response to ground reaction forces and is in a weakened state. A sharp increase in weekly training load compared to the preceding four weeks dramatically increases the risk of hamstring strain injury. Additionally, athletes who experience a spike in high intensity running loads greater than their average output of the previous 2 years are also at a heightened risk.

Conclusion

As you can see there a number of contributing factors that impact on why the injury occurred. An important thing to remember is that when you are pushing your body to the absolute limits and pushing the boundaries there is going to be an increased risk to injury.

We just want to make sure we do all we can to build strong robust athletes that are resilient to injury.

Stay tuned, with our following hamstring series posts going into detail on how to bullet proof your hamstrings and then providing an insight to hamstring injury rehabilitation.