Assessment of acute neuromuscular fatigue manifestations and functional performances after heavy resistance exercise

BACKGROUND: This study aimed to assess neuromuscular fatigue after heavy resistance exercise in rugby players. METHODS: Twelve male rugby players performed five sets of knee extension exercise lifting 80% of their one repetition maximum until failure, with 3min of rest in-between. Maximal voluntary contraction (MVC) and surface electromyographic activity from quadriceps muscles, as well as ions (i.e., Na⁺, K⁺, and Cl-) and metabolic responses (i.e., blood lactate and ammonia concentrations) were measured before and after exercise. Maximum repetitions performance and both peripheral (RPE_p) and overall body (RPE_o) rating of perceived exertion were recorded following each set. RESULTS: The number of maximum repetitions decreased significantly across sets (P<0.001). Both RPE_p and RPE_o increased significantly across sets (P<0.001) with higher RPE_p values after each set (P<0.001). Both RPE_p (r=-0.98, P<0.01) and RPE_o (r=-0.99, P<0.001) were negatively correlated with the changes in the number of maximum repetitions. MVC (P<0.001), root mean square (P<0.05), and neuromuscular efficiency (P<0.01) as well as Na⁺ (P<0.01), Cl- (P<0.001) and blood concentrations of lactate (P<0.001) and ammonia (P<0.001) increased significantly after the exercise. However, K⁺ (P<0.001) increased after the resistance exercise. CONCLUSIONS: Heavy resistance exercise affected both objective (i.e., neuromuscular and biochemical parameters) and subjective (i.e., RPE) aspects of neuromuscular fatigue.