Assessing fatigue in football

As levels of fatigue rise in football, so does injury risk. With that in mind, British scientists have been investigating the effects of fatigue in football on the ratio of hamstrings strength to quadriceps strength (relatively weak hamstrings are know to increase injury risk). To do this, they used a field test based on the Loughborough Intermittent Shuttle Test (LIST) to induce fatigue and then examined the ratio of hamstrings to quadriceps strength in the dominant and non-dominant legs at two different velocities of muscle contraction.

Eight male football players who played at British University Southern Conference level performed a pre-test to assess the concentric and eccentric strength of the hamstrings and the quadriceps. This was performed on an isokinetic resistance machine at two velocities – 60 and 180 degrees per second of movement about the knee joint. Following this pre-test, shuttle running took place to simulate the demands of a football match and then the hamstring/quadriceps testing protocol was repeated.

The main findings demonstrated significant decreases in the conventional hamstrings/quadriceps ratio (calculated as the maximal concentric hamstrings strength divided by the maximal concentric quadriceps strength) in the dominant leg at 180 degrees per second, and in the functional hamstrings/quadriceps ratio (calculated as the maximal eccentric hamstrings strength divided by the maximal concentric quadriceps strength) in the dominant leg at 60 degrees and 180 degrees per second. Put simply, both tests showed that the hamstrings became relatively weaker following shuttle running (increasing injury risk).

Moreover, significant correlations were observed between physiological parameters measured during the football-specific exercise and the functional hamstrings/quadriceps ratio. This suggests that the functional ratio is more representative of fatigue induced by football than the conventional ratio and that eccentric strength training at high velocities may be necessary to reduce injury risk in football players.

Int J Sports Med. 2010 Feb 15. (Epub ahead of print)