Isokinetic and isometric muscle function of the knee extensors and flexors during simulated soccer activity: Effect of exercise and dehydration

This study investigated the influence of dehydration during soccer-type intermittent exercise on isokinetic and isometric muscle function. Eight soccer players performed two 90-min high-intensity intermittent shuttle-running trials without (NF) or with (FL) fluid ingestion (5ml center dot kg1 before and 2ml center dot kg1 every 15min). Isokinetic and isometric strength and muscular power of knee flexors and knee extensors were measured pre-exercise, at half-time and post-exercise using isokinetic dynamometry. Sprint performance was monitored throughout the simulated-soccer exercise. Isokinetic knee strength was reduced at faster (3.13 rad center dot s1; P=0.009) but not slower (1.05 rad center dot s1; P=0.063) contraction speeds with exercise; however, there was no difference between FL and NF. Peak isometric strength of the knee extensors (P=0.002) but not the knee flexors (P=0.065) was significantly reduced with exercise with no difference between FL and NF. Average muscular power was reduced over time at both 1.05 rad center dot s1 (P=0.01) and 3.14 rad center dot s1 (P=0.033) but was not different between FL and NF. Mean 15-m sprint time increased with duration of exercise (P=0.005) but was not different between FL and NF. In summary, fluid ingestion during 90min of soccer-type exercise was unable to offset the reduction in isokinetic and isometric strength and muscular power of the knee extensors and flexors.