Muscular heat shock protein response and muscle damage after semi-professional football match.

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A typical football match leads to neuromuscular fatigue and physical performance impairments up to 72-96h post-match. While muscle damage is thought to be a major factor, damage on the ultrastructural level has never been documented. The purpose of this study was to investigate post-match cellular muscle damage by quantifying the heat shock protein (HSP) response as a proxy for protein damage. Muscle biopsies, blood samples, countermovement jumps, and perception of muscle soreness were obtained from twelve semi-professional football players 1, 24, 48, and 72h after a 90-min football match. Muscle biopsies were analyzed for αB-crystallin and HSP70 in the cytosolic and cytoskeletal sub-cellular fractions by Western blotting. Fiber type-specific αB-crystallin and HSP70staining intensity, and tenascin-C immunoreactivity were analyzed with immunohistochemistry. Blood samples were analyzed for creatine kinase and myoglobin. Within 24h post-match, a 2.7- and 9.9-fold increase in creatine kinase and myoglobin were observed, countermovement jump performance decreased by -9.7% and muscle soreness increased by 0.68 units. αB-crystallin and HSP70 accumulated in cytoskeletal structures evident by a 3.6- and 1.8-fold increase in the cytoskeletal fraction and a parallel decrease in the cytosolic fraction. In type I and II fibers, αB-crystallin staining intensity increased by 15%-41% and remained elevated at 72h post-match. Lastly, the percentage of fibers with granular staining of αB-crystallin increased 2.2-fold. Football match play induced a muscular HSP stress response 1-72h post-match. Specifically, the accumulation of HSPs in cytoskeletal structures and the granular staining of αB-crystallin suggests occurrence of ultrastructural damage. The damage, indicated by the HSP response, might be one reason for the typically 72h decrease in force-generating capacity after football matches.