STRENGTH AND CONDITIONING

CONDITIONING THE HAMSTRINGS:

TRAINING CONSIDERATIONS FOR PERFORMANCE AND INJURY PREVENTION

By Dr Duncan N. French

Various mechanisms have been hypothesised as the cause of susceptibility to hamstring strain and injury; including strength imbalances between the quadricep and hamstring muscle groups, weak hamstrings, tight or inflexible hamstrings, and asynchronous firing of the nerves that innervate the hamstring complex (1). What is apparent, however, is that even with the many paradigms surrounding the underlying cause of susceptibility to hamstring injury, ‘weakness’ or ‘lack of strength’ of the hamstring muscles receives the most attention from athletes, coaches and trainers alike. Indeed muscle strength and crucially the length-tension relationship of the hamstrings (ie. the joint angle at which peak force occurs), is now recognised as a critical factor in the prevention of muscle strains and injury (2).

sportEX has produced an animated movie outlining the hamstring muscle actions along with origins and insertions. See the end of the article for more info (i-1).

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The majority of hamstring strains occur as muscles

move into a lengthened position whilst also experiencing high tensile loads.

The hamstrings themselves are most active during the late swing phase, through early to mid-stance phase

of the running gait cycle (2) (i-2). They act to decelerate the forward momentum of the leg and reverse the swing action via active hip extension. During the late swing phase, the bicep femoris experiences a great degree of mechanical stretch, thereby becoming susceptible to specific injuries related to the ‘lengthen- ing’ of the musculotendon unit. In listening to athletes who have experienced hamstring strains many report that their injury occurred as a result of acting to decelerate their body or working their limbs through an exaggerated range of motion as they

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INTRODUCTION There are many theories concerning the underlying cause of hamstring injuries but whatever the cause, strength training plays an important part in the prevention of injury. The mechanism of injury is often eccentric deceleration activity therefore training should functionally reflect both this and the two joint actions of the muscles especially their role as hip extensors. Whilst lying leg curls and similar exercises which isolate the muscle group can contribute, they should not form the foundation of a hamstring strengthening programme. Exercises should be multi-joint, open and closed kinetic chain with a predominance of eccentric action targeting hamstrings and the gluteals and include the stretch-shortening characteristics of the late swing phase of running. This article outlines six examples of specific exercises for hamstring strengthening.

emphasised their stride length during a sprinting action. The majority of hamstring strains occur during the eccentric actions of the “blocking” and “plant” phases of running gait, with most occurring during the plant phase as muscles move into a lengthened position whilst also experiencing high tensile loads. Training of the hamstrings to manage these forces should therefore be a critical part of any athletes preparatory activities.

HAMSTRING MUSCLE FUNCTION Muscle architecture dictates its function, which in turn should dictate the coach’s approach to physical conditioning. The hamstring muscle is pennate in nature and is composed primarily of type II fibres, which are designed for high speed, forceful muscle actions (3). The nature of injury and the phase in the stride cycle where injury commonly occurs are a good indication of hamstring function, as well as an insight into the mechanism of the injury itself. Gambetta & Benton (4) indicate that despite clear evidence of hamstring function, and the biarticular nature of the hamstrings, there is a continued search for ways to isolate the

sportEX dynamics 2008;15(Jan):18-22