The effect of exercise induced hyperthermia on muscle fibre conduction velocity during sustained isometric contraction

This study investigated the effect of dynamic exercise in a hot environment on muscle fibre conduction velocity (MFCV) of the knee extensors during a sustained isometric contraction. Seven trained male cyclists (mean [±SD], age, and V_ O2max were 35 ± 9.9 and 57.4 ± 6.6 ml kg1 min1) cycled for 50 min at 60% of peak power output in either: (1) 40 C (HOT); or (2) 19 C (NEUTRO); and (3) remained passive in 40 C (PASS). Post-intervention a 100 s maximal sustained isometric contraction (SMC) of the knee extensors was performed. Rectal temperature increased (p < 0.01) for both HOT and NEUTRO with PASS unchanged and with HOT rising higher (p < 0.01) than NEUTRO (38.6 ± 0.4 vs. 37.6 ± 0.4 C). Muscle temperature increased (p < 0.01) for all three conditions with HOT rising the highest (p < 0.01) (40.3 ± 0.5 vs. 38.3 ± 0.3 and 37.6 ± 1.3 C for NEUTRO and PASS, respectively). Lactate showed higher accumulation (p < 0.01) for HOT than NEUTRO (6.9 ± 2.3 vs. 4.2 ± 2.1 mmol l1). During SMC the torque, electromyography root mean squared (RMS) and MFCV all significantly (p < 0.01) declined. Only in HOT did MFCV decline significantly (p < 0.01) less than torque and RMS (9.9 ± 6.2% vs. 37.5 ± 17.8% and 37.6 ± 21.4%, respectively). In conclusion, during exercise induced hyperthermia, reduced motor unit recruitment as opposed to slower conducting properties of the muscle fibre appears to be responsible for the greater reduction in torque output

Effects of exercise training on performance and function in individuals with cerebral palsy: A critical review

This critical review article describes the exercise performance capabilities, and the effect of exercise training interventions, in individuals with cerebral palsy (CP). A literature search was conducted using PubMed, Medline, Embase, Scopus, Web of Science, Science Direct and Google Scholar databases from the earliest possible date to December 2014. Large impairments in exercise performance have been reported in individuals with CP, as well as large improvements following the implementation of training interventions. The physiology underlying the functional and physical impairments in CP were also reviewed, and grouped into categories, namely: motor impairments, central impairment, skeletal muscle morphology and physical inactivity. Although much research exists on individuals with CP, there is conflicting evidence for the benefits of exercise training in these individuals. This is due to the use of sedentary, paediatric populations and varied methodologies. Investigating individuals who have undergone high-volume exercise training from a young age might result in a better understanding of functional and physical performance in individuals with CP.Key words: Disability; Physical activity; Rehabilitation; Physiology