Exacerbated impairments in neuromuscular function when two bouts of team sport match simulations are separated by 48h.

Abstract

Intermittent team sports, involving high metabolic and mechanical demands, elicit prolonged impairments in neuromuscular function which persist for ∼48-72h. Whether impairments in neuromuscular function are exacerbated when such exercise is repeated with incomplete recovery is unknown. This study assessed the neuromuscular, heart rate and metabolic responses to two bouts of ∼90min modified team sport match simulations separated by 48h in 12 competitive football players. Before and 2min after both bouts, knee extensor isometric maximal voluntary contraction (MVC), contractile function (Qtw,pot ) and voluntary activation (VA) were measured. Heart rate (HR), sprint time, blood lactate and glucose were measured throughout both bouts. MVC was reduced relative to baseline at post-bout 1 (21±12%; P=0.003) and pre-bout 2 (14±11%; P=0.009), and was lower post-bout 2 (33±14%; P<0.001) relative to post-bout 1 (P=0.036). Qtw,pot was reduced post-bout 1 (30±11%; P<0.001) and pre-bout 2 (9±6%; P=0.004), and was not different post-bout 2 (28±8%; P<0.001) relative to post-bout 1 (P=0.872). VA was reduced post-bout 1 (8±7%; P=0.023), recovered pre-bout 2 (P=0.133) and was lower post-bout 2 (16±7%; P<0.001) relative to post-bout 1 (P=0.029). Total sprint time was longer, and HR, blood lactate and glucose were lower during bout 2 than bout 1 (P≤0.021). Thus, impairments in neuromuscular function are exacerbated when high-intensity intermittent exercise is performed with incomplete recovery concurrent with accentuated reductions in VA. The lower blood lactate and glucose during the second bout might be due, at least in part, to reduced glycogen availability upon commencing exercise and consequently a greater reliance on glucose extraction. NEW FINDINGS: What is the central question of this study? There is limited evidence on whether impairments in neuromuscular function are exacerbated when prolonged high-intensity intermittent exercise is repeated with incomplete recovery: what are the neuromuscular consequences of performing two bouts of a modified team sport match simulations separated by 48h? What is the main finding and its importance? Impairments in knee extensor force generating capacity are exacerbated concurrent with accentuated reductions in nervous system activation of muscle when prolonged high-intensity intermittent exercise is repeated with 48h recovery.