Influence of soccer-specific fatigue on knee joint kinematics during dynamic landings

OBJECTIVE Epidemiological data suggests that more soccer injuries occur during the latter stages of match-play, with fatigue cited as a contributing factor. Primary non-contact injury mechanisms include landing and turning. Single legged hopping tasks are often used to investigate the mechanisms of injury, but typically in the rested state with no ©Journal of Sports Science and Medicine (2007) Suppl. 10 http://www.jssm.org 149 consideration given to the influence of fatigue. The aim was to investigate the time-course of soccer-specific fatigue on knee joint kinematics during single legged hopping tasks (inversion cut, eversion cut and planar hop for height). The exercise protocol was based on notational analyses of match-play. The hopping tasks were representative of the multidirectional nature of soccer, and the pre-habilitative work conducted during training. METHODS Eight professional soccer players completed a 90 min treadmill protocol, comprising six repetitions of a 15 min activity bout and a 15 min passive half-time interval. At rest, and subsequently at 15 min intervals, each player completed the three hopping trials in randomised order. Frontal and sagittal plane knee joint kinematics were quantified during landing using automated motion analysis. RESULTS Knee joint kinematics at touchdown were characterised by flexion (~30°) and varus (~7°). Knee flexion at touchdown was not affected (P≥0.05) by exercise duration, but varus tended to increase during the simulated match. The increase in varus during the landing phase was greatest in the inversion hop. Knee varus during the planar hop for height was affected by the passive half-time interval.