Locomotor muscle fatigue is not critically regulated after prior upper body exercise.
This study examined the effects of prior upper body exercise on subsequent high-intensity cycling exercise tolerance and associated changes in neuromuscular function and perceptual responses. Eight men performed three fixed work-rate (85% peak power) cycling tests: 1) to the limit of tolerance (CYC); 2) to the limit of tolerance after prior high-intensity arm-cranking exercise (ARM-CYC); and 3) without prior exercise and for an equal duration as ARM-CYC (ISOTIME). Peripheral fatigue was assessed via changes in potentiated quadriceps twitch force during supramaximal electrical femoral nerve stimulation. Voluntary activation was assessed using twitch interpolation during maximal voluntary contractions. Cycling time during ARM-CYC and ISOTIME (4.33 ± 1.10 min) was 38% shorter than during CYC (7.46 ± 2.79 min) (P < 0.001). Twitch force decreased more after CYC (-38 ± 13%) than ARM-CYC (-26 ± 10%) (P = 0.004) and ISOTIME (-24 ± 10%) (P = 0.003). Voluntary activation was 94 ± 5% at rest and decreased after CYC (89 ± 9%, P = 0.012) and ARM-CYC (91 ± 8%, P = 0.047). Rating of perceived exertion for limb discomfort increased more quickly during cycling in ARM-CYC [1.83 ± 0.46 arbitrary units (AU)/min] than CYC (1.10 ± 0.38 AU/min, P = 0.003) and ISOTIME (1.05 ± 0.43 AU/min, P = 0.002), and this was correlated with the reduced cycling time in ARM-CYC (r = -0.72, P = 0.045). In conclusion, cycling exercise tolerance after prior upper body exercise is potentially mediated by central fatigue and intolerable levels of sensory perception rather than a critical peripheral fatigue limit.
Sport, Health and Performance Enhancement (SHAPE) Research Group, Department of Sports Science, School of Science and Technology, Nottingham Trent University, Nottingham, United Kingdom; and Michael.johnson@ntu.ac.uk.
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Johnson
Sport, Health and Performance Enhancement (SHAPE) Research Group, Department of Sports Science, School of Science and Technology, Nottingham Trent University, Nottingham, United Kingdom; and.
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Sharpe
Sport, Health and Performance Enhancement (SHAPE) Research Group, Department of Sports Science, School of Science and Technology, Nottingham Trent University, Nottingham, United Kingdom; and.
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Williams
Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, London, United Kingdom.
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Hannah
D000328:Adult; D001132:Arm / Q000502:physiology; D004558:Electric Stimulation; D004576:Electromyography; D015444:Exercise / Q000502:physiology*; D017079:Exercise Tolerance; D005267:Femoral Nerve / Q000502:physiology; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007866:Leg / Q000502:physiology; D008124:Locomotion / Q000502:physiology*; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018763:Muscle Fatigue / Q000502:physiology*; D053581:Muscle Strength Dynamometer; D018482:Muscle, Skeletal / Q000502:physiology*; D055815:Young Adult
central fatigue; exercise tolerance; perceived exertion; peripheral fatigue