Hamstring tears occur typically in sprinting especially when leaning forward possibly to pick up a ball or kick it. Injury is a common occurrence through rapid, active extension of the knee, which activates eccentric action in the hamstrings decelerating the lower leg in the late swing phase. It has also been suggested that the hamstring muscles are vulnerable
to injury during the rapid change from their eccentric to concentric action, when they become active hip extensors. At some exercise intensity, the player surpasses the mechanical limits tolerated by the muscle unit.
They occur more often in the older player and in players who have already suffered a previous leg injury. As with all sport injuries the incidence increases with the hours of play and the level played at. In rugby the incidence has been shown to be 5.6 injuries per 1000 hours of play and in semi-professional soccer players at 3.0 injuries per 1000 hours of play. There is evidence that injuries occur more often in the second half of games and perhaps a warm up after half time would be a good idea. High volumes of training in the week preceding a match have been shown to increase the incidence of muscle tears. The reinjury rate could be up to 30.
Passive and active warm-up and muscle stretching before training and competition have been advocated as effective injury-prevention strategies, even though there is limited evidence to demonstrate that these activities reduce the incidence of muscle strains.
Hamstring strengthening has been shown to reduce the incidence of hamstring muscle strains. In our experience at the Sports Injury Surgery athletes in Ireland playing at relatively high levels in all sports have poor hamstring strength as measured by Biodex Isokinetic Testing and have an imbalance between their Quadriceps and their Hamstrings with an overemphasis on quadriceps muscle strength.
We have also found that core stability and proprioception is poor. It has been shown that training in core stability and proprioception will reduce the incidence of muscle tears in the legs.
Studies have also shown that identification of muscle imbalances with an isokinetic measuring device such as the Biodex and then correcting these imbalances with a focused training programme will reduce the risk of hamstring muscle tears.
We advocate the use of the Nordic Hamstring Strengthening exercises to reduce the risk of tears and then retesting on the Biodex machine to prove that the hamstring muscles have indeed strengthened.
Tears can also be treated in the initial stages with platelet injections. see Platelet Therapy for more information. This technique uses the body’s own growth factors in the blood to promote healing.