Recovery of kicking kinematics and performance following intermittent high-intensity running bouts in young soccer players: can a local cooling intervention help?

Repeated high-intensity running (RHIR) exercise is known to affect central and peripheral functioning. Declines in RHIR performance are exacerbated by environmental heat stress. Accordingly, the use of post-exercise cooling strategies (COOL) is recommended as it may assist recovery. The present study aimed to investigate, in a hot environment (> 30{o}C), the effects of local COOL following RHIR on indices of soccer kicking movement and performance in youth soccer. Fifteen academy under-17 players (16.27 {+/-} 0.86 years-old; all post-PHV), acting as their own controls, participated. In #Experiment 1, players completed an all-out RHIR protocol (10 x 30 m bouts interspersed with 30 s intervals). In #Experiment 2, the same players performed the same running protocol under two conditions, 1) 5 minutes of COOL where ice packs were applied to the quadriceps and hamstrings regions and, 2) a control condition involving only passive resting. In both experiments, perceptual measures [ratings of perceived exertion (RPE), pain and recovery], thigh temperature and kick-derived video kinematics (hip, knee, ankle and foot) and performance (ball speed and placement) were collected at baseline and post exercise and intervention. In the first experiment, RHIR led to moderate-to-large increases (p < 0.03) in RPE (d = 4.08), ankle eversion/inversion angle (d = 0.78) and mean radial error (d = 1.50) and small-to-large decreases (p < 0.04) in recovery (d = -1.83) and average/peak ball speeds (d = -0.42--0.36). In the second experiment RPE (p < 0.01; Kendalls W = 0.30) and mean radial error (p = 0.057; {eta}2 = 0.234) increased only post-control. Significant small declines in ball speed were also observed only post-control (p < 0.05; d = 0.35). Post-intervention CMfoot velocity was moderately faster in COOL as compared to control (p = 0.04; d = 0.60). RHIR acutely impaired kicking movement, ball speed and placement in youth soccer players. However, a short period of local cryotherapy may be beneficial in counteracting declines in indices of kicking performance in hot environment. Trial registration number#RBR-8prx2m - ReBEC Brazilian Clinical Trials Registry