Fatigue and recovery of central nervous system function following intermittent-sprint exercise

Brownstein, Callum (2018) Fatigue and recovery of central nervous system function following intermittent-sprint exercise. Doctoral thesis, Northumbria University.

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Abstract

Research into fatigue following sports characterised by intermittent sprint exercise has increased substantially in recent years. However, when investigating post-exercise impairments in muscle function and recovery thereof, studies have predominantly focused on peripheral perturbations. The aim of this thesis was to examine the aetiology of impairments in neuromuscular function which occur following intermittent sprint exercise, with a focus on both peripheral and central perturbations. Study 1 determined the optimal protocol for the measurement of corticospinal excitability (CSE), short-interval intracortical inhibition (SICI), and intracortical facilitation (ICF) in the rectus femoris using transcranial magnetic stimulation (TMS). Study 2 examined the reliability of single- and paired-pulse TMS measures, as well as the reliability of measures of neuromuscular and physical function and perceptual assessments, when measured within-day and on consecutive days. These studies informed the methodology of subsequent chapters, and demonstrated that these variables could be assessed reliability within- and between-days. Study 3 examined the aetiology and recovery of perturbations in neuromuscular function following competitive football match-play. The study demonstrated that football match-play elicited substantial post-match impairments in isometric maximal voluntary contraction (MVC) strength of the knee extensors (-14%, P < 0.001) that persisted for 48 h (-4%, P = 0.01), before recovering by 72 h post-exercise. In addition, match-play elicited protracted impairments in contractile function, as demonstrated through considerable post-match reductions in potentiated twitch force (−14%; P < 0.001), which persisted at 24 h (−6%; P = 0.01) before recovering by 48 h. Furthermore, match-play evoked prolonged impairment in central nervous system (CNS) function, with a decline in the capacity of the CNS to voluntarily activate muscle post-match (−8%; P < 0.001), which persisted at 24 h (−5%; P = 0.01) and required up to 48 h to recover. Study 3 implemented a novel method of cryotherapy using phase change material (PCM) in an attempt to accelerate recovery following match-play. The study showed that wearing cold PCM garments had no effect on recovery when compared with a placebo control. These studies provide novel insight into the aetiology of fatigue following intermittent sprint exercise, which elicits prolonged impairments in CNS function, requiring up to 48 h to resolve.

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