LA FATICA NEUROMUSCOLARE NEL CALCIO: ASPETTI CENTRALI E PERIFERICI

Soccer is a team sport that requires prolonged high-intensity intermittent exercise. Physical aspects of match performance have changed a lot in the last forty years; for example total distance has increased from 7000-8000 m in the seventies to 10000-11000 m reported in recent investigations. Nowadays, during the match, players change activity on average every 5 seconds and perform approximately 1300 actions, with 200 of these being completed at high-intensity. In addition, the game involves other intense actions such as decelerations, kicking, dribbling, and tackling. All of these efforts exacerbate the physical strain imposed on the players and contribute to making football highly physiologically demanding. Furthermore, soccer players that compete at high level perform up to 70 matches during a single season. During the second half of a match, the total distance and high-intensity running decline markedly, with the amount of high-intensity running 20% to 40% lower in the last 15 min of the game compared with the initial 15-min period. A greater decrement in running is observed when more activity is performed in the first half. Furthermore, in the 5-min period following the most demanding 5-min of the game, the distance covered at high intensity is reduced by 6% to 12% compared with the game average. Collectively, these results indicate that players experience fatigue toward the end of a match and temporarily during a game. Accordingly, both single and repeated-sprint test performances are impaired after a high-intensity period during as well as at the end of the game. Fatigue may also have a negative impact on passing precision, with the less fit players showing a more pronounced deterioration in technical performance. Furthermore, maximal strength and jumping ability are also both reduced immediately after a match. The time required for a full recovery of these qualities in male players may be very long (> 72 h) (permanent fatigue). However, there is limited information regarding recovery time in high level athletes. In literature, fatigue can be defined as an acute impairment of performance that includes both an increase in the perceived of the effort necessary to exert a desired force or power and/or reduction in the ability to exert maximal force or power. It has been demonstrated that the neuromuscular mechanisms that contribute to performance impairment differ according to the contraction mode, exercise intensity and the duration. Fatigue can be classified as central when the origin is proximal and/or peripheral when the origin is distal to the neuromuscular junction. However, to date, no studies have quantified the relative contribution of central and peripheral factors in determining fatigue in soccer. Peripheral skeletal muscle function can be determined using electrical stimulations and classified as high-frequency and low-frequency (or long-lasting fatigue). Long-lasting fatigue can be evaluated using tetanic nerve stimulations at different frequencies (low- to high-frequency force ratio). Nonetheless,…