Greig, M. (2010). A biomechanical rationale for soccer half-time re-warm-up strategies. Presentation 698 at the 2010 Annual Meeting of the American College of Sports Medicine, Baltimore, Maryland; June 2-5.

"In professional soccer match-play, the initial stages of the second half are characterized by a reduction in high intensity distance covered and a high incidence of injury." This study attempted to provide a biomechanical rationale for a half-time re-warm-up. Semi-professional soccer players (N = 10) completed three simulated games on an intermittent treadmill protocol replicating the physical demands of match-play. During each game simulation, at 15-minute intervals, each S completed tasks comprising: isokinetic (eccentric and concentric) testing of the knee flexors and extensors (180, 300 and 60º/sec); a planar hop with knee joint kinematic analysis (200 Hz); or single-leg dynamic balance tasks in response to a system perturbed by rotation. Ss completed a passive 15-minute half-time period.

At the start of the simulated second half, there was a significant decrease in eccentric hamstring peak torque relative to pre-exercise values, the decrease being more marked at the fastest test speeds. The coincident planar hop trial recorded the greatest degree of knee-varus displacement during flexion. Impaired dynamic reactive balance after half-time was also observed, with changes in both the magnitude and pattern of centre of gravity displacement. There was a significantly increased deviation in the anterior-posterior plane during recovery from an enforced inversion movement, and significantly increased medio-lateral displacement in reaction to an enforced plantar flexion movement.

Implication. Impaired mechanical performance at the start of a simulated second half across a range of tasks supported epidemiological observations. For eccentric hamstring strength and knee varus displacement during landing, a fatigue effect developed during the first half did not recover during the half-time period. For dynamic reactive balance the impairment was attributed to the passive interval, with no preceding fatigue effect. Recovery/warm-up activities should be pursued during half-time intervals in soccer matches, and probably in any game that employs such stoppages.

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