Twist, C. (2009). Variations in isokinetic strength loss following plyometric exercise. A paper presented at the 14th Annual Congress of the European College of Sport Science, Oslo, Norway, June 24-27.

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"A reduction in maximal voluntary isometric force is considered to be one of the most appropriate indirect markers of exercise-induced muscle damage. Although isometric force loss is known to demonstrate large between subject variations following eccentric-biased exercise, the variations in isokinetic strength loss are less clearly understood. Furthermore, there is little known about the inter-subject responses to force loss induced by modes of eccentric-biased exercise commonly adopted in athletic training."

This study investigated the variations in isokinetic strength loss following plyometric exercise. Ss (N = 16) were recreationally active and had no history of resistance training in the previous six months. Peak isokinetic torque of the knee extensors was measured at 60 deg/s. In addition, perceived muscle soreness was recorded on a 010 visual analogue scale. All measurements were taken before and then at 24 and 48 hours following 10 x 10 countermovement jumps. A cluster analysis of peak torque data at 48 hours was used to objectively establish high- and low-responders to plyometric exercise.

At baseline, high- and low-responders to plyometric exercise demonstrated no differences in body mass or age, although stature was significantly higher in the high-responder group. Gender distribution was different between groups (low-responders 67% females; high-responders 10% females). There was a significant group by time interaction for peak isokinetic torque. Reductions in isokinetic peak torque for high-responders was ~22% and for low-responders ~7%. There was no difference in perceived muscle soreness between groups. The magnitude of force loss was lower than reported in previous publications.

Implication. Inter-subject variations in isokinetic force loss occur following plyometric exercise, although notable differences do not occur between high- and low-responders in subjective markers of perceived muscle soreness. Gender distribution might explain some of the observed variations, with a larger proportion of males in the high-responder group.

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