The acute effects of graded physiological strain on soccer kicking performance: a randomized, controlled cross-over study

Purpose The aim of the present study was to examine the acute effects of graded physiological strain on soccer kicking performance. Methods Twenty-eight semi-professional soccer players completed both experimental and control procedure. The experimental protocol incorporated repeated shooting trials combined with a progressive discontinuous maximal shuttle-run intervention. The initial running velocity was 8 km/h and increasing for 1 km/h every 3 min until exhaustion. The control protocol comprised only eight subsequent shooting trials. The soccer-specific kicking accuracy (KA; average distance from the ball-entry point to the goal center), kicking velocity (KV), and kicking quality (KQ; kicking accuracy divided by the time elapsed from hitting the ball to the point of entry) were evaluated via reproducible and valid test over five individually determined exercise intensity zones. Results Compared with baseline or exercise at intensities below the second lactate threshold (LT2), physiological exertion above the LT2 (blood lactate >4 mmol/L) resulted in meaningful decrease in KA (11-13 %; p < 0.05), KV (3-4 %; p < 0.05), and overall KQ (13-15 %; p < 0.01). The light and moderate-intensity exercise below the LT2 had no significant effect on soccer kicking performance. Conclusions The results suggest that high-intensity physiological exertion above the player's LT2 impairs soccer kicking performance. In contrast, light to moderate physiological stress appears to be neither harmful nor beneficial for kicking performance.