Muscle injuries account for up to 1/3 of all sports related injuries, and can lead to extended periods of time out of sport. It is crucial to be able to diagnose the extent of injury so patients can be rehabilitated accordingly to return them to sport as quickly as possible. Ultrasonography and magnetic resonance imaging are effective methods of diagnosing injury, particularly when it is unclear.
The most common mechanism of muscle damage is via indirect injury. Muscles are at risk during the period when they are being lengthened and load is applied. Try to imagine running downhill, and when your foot is coming through to the ground, your Hamstrings will be loaded in a stretched position. Acute muscle injuries are often associated with both sprinting and stretching activities. With sprinting-related muscle injuries, there is initially profound loss of function, but with faster recovery. The opposite applies for stretching-related injuries where the initial loss of function is reduced, but recovery is longer. There are a number of factors that increase the risk of indirect muscle injury, and they include:
# eccentric contraction
# injury to muscles with a high concentration of fast twitch type II fibres
# a sudden change in muscle function
# muscles crossing two joints (Hamstrings and Calf muscles)
# failure to absorb or counteract forces from other muscle groups or ground reaction
# muscle imbalance
Muscle strains may be categorised into grade 1, less than 5% loss of function or strength; grade 2, where there is soft tissue damage, reduced strength and some residual strength; and grade 3, a complete tear with complete loss of function and palpable gap between the tendon and muscle. Once the degree of injury has been diagnosed, then the appropriate rehabilitation programme can be implemented.