Managing the combined consequences of COVID-19 infection and lock-down policies on athletes: narrative review and guidelines proposal for a safe return to sport.

COVID-19 pandemic is a global health matter. The disease spread rapidly across the globe and brought the world of sports to an unprecedented stoppage. Usual symptoms of the disease are fever, cough, myalgia, fatigue, slight dyspnoea, sore throat and headache. In more severe cases, dyspnoea, hypoxaemia, respiratory failure, shock and multiorgan failure occur. This appears to be a self-limiting phenomenon related to individuals with coexisting medical conditions, such as hypertension, diabetes and cardiovascular disorders. Nevertheless, cases have been reported in professional soccer players in extremely good fitness condition, demonstrating that athletes are not spared by the disease. Despite COVID-19 clinical manifestations are mainly respiratory, major cardiac complications are being reported, leading to acute myocarditis. One difficulty is that symptoms of COVID-19 vary among individuals, with athletes being affected with no apparent sign of the disease. This could be a real danger for amateur or professional athletes when returning to their usual training and thus to play. Another threat is that the lock-down policies did not allow most athletes to follow their usual training routines. There is thus a need for a careful approach by the sports medicine community to ensure safety of all athletes before they return to sport. Here, we propose evaluation guidelines of fitness and health of athletes to (1) reduce any lethal risk of practice, especially myocarditis and sudden cardiac death; (2) evaluate the combined consequences of the disease and detraining on the physical abilities and biological profile of athletes; and (3) monitor postinfection fatigue symptoms.

Effects of string stiffness on muscle fatigue after a simulated tennis match.

We tested the influence of string stiffness on the occurrence of forearm muscle fatigue during a tennis match. Sixteen tennis players performed two prolonged simulated tennis matches with low-stiffness or high-stiffness string. Before and immediately after exercise, muscle fatigability was evaluated on the forearm muscles during a maximal intermittent gripping task. Groundstroke ball speeds and the profile of acceleration of the racquet frame at collision were recorded during each match. The peak-to-peak amplitude of acceleration and the resonant frequency of the frame were significantly greater with high- (5060 ± 1892 m/s(2) and 204 ± 29 Hz, respectively) than with low-stiffness string (4704 ± 1671 m/s(2) and 191 ± 16 Hz, respectively). The maximal and the averaged gripping forces developed during the gripping task were significantly reduced after the tennis match with high- (-15 ± 14%, and -22 ± 14%, respectively), but not with low-stiffness string. The decrease of ball speed during the simulated matches tended to be greater with high- than with low-stiffness string (P = .06). Hence, playing tennis with high-stiffness string promotes forearm muscle fatigue development, which could partly contribute to the groundstroke ball speed decrement during the game.

Effect of playing surface properties on neuromuscular fatigue in tennis.

PURPOSE: The aim of this study was to evaluate the effect of the playing surface properties on the development of neuromuscular fatigue in tennis. METHODS: Ten subjects played randomly two tennis matches on hard court (HARD) and clay court (CLAY) for an effective playing duration of 45 min (i.e., corresponding approximately to a 3-h game). Before and after each match, the maximal voluntary contraction (MVC) force of the plantar flexors, the maximal voluntary activation level, the maximal compound muscle action characteristic, and the EMG activity were determined on the soleus (SOL) and lateralis gastrocnemius (LG) muscles. Tetanic and single stimulations were also delivered to evaluate the presence of low-frequency fatigue and contractile impairment. Finally, reflex responses were evoked on the relaxed muscle (H-reflex) and during MVC (H-reflex and V-wave). RESULTS: Statistical analysis did not reveal any significant difference between playing surfaces. MVC was similarly reduced after the game (HARD, -9.1% ± 8.7%; CLAY, -4.3% ± 19.9%) and was associated with alterations of the contractile properties of the plantar flexor muscles. The implication of central factors was less clear, as evidenced by the significant reduction (P < 0.05) of the H-reflex on the relaxed LG (HARD, -16.2% ± 33.3%; CLAY, -23.9% ± 54.0%) and SOL (HARD, -16.1% ± 48.9%; CLAY, -34.9% ± 35.9%) and the nonsignificant reduction of the activation level. In addition, the reflex responses evoked during MVC were not significantly modified by the exercise. CONCLUSION: These results suggest that the ground surface properties influence neither the extent nor the origin of neuromuscular fatigue in tennis. The moderate force decrement observed in the current study was mainly associated with peripheral fatigue.