Intensity-dependent Contribution of Neuromuscular Fatigue after Constant-Load Cycling

Thomas, Kevin, Elmeua, Marc, Howatson, Glyn and Goodall, Stuart (2016) Intensity-dependent Contribution of Neuromuscular Fatigue after Constant-Load Cycling. Medicine and Science in Sports and Exercise, 48 (9). pp. 1751-1760. ISSN 0195-9131

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Purpose: We tested the hypothesis that central and peripheral fatigue after constant-load cycling exercise would vary with exercise intensity and duration.

Methods: Twelve well-trained male cyclists (V·O2max, 4.49 ± 0.35 L·min-1) completed three constant-load cycling trials to the limit of tolerance in a randomized crossover design. Exercise intensities were set according to the respiratory responses to a preliminary ramp test to elicit cardiorespiratory and metabolic responses consistent with exercise in the severe and heavy exercise domains: 1) at power at V·O2max (S+, 379 ± 31 W), 2) at 60% of the difference between gas exchange threshold and V·O2max (S-, 305 ± 23 W), and 3) at the respiratory compensation point (RCP, 254 ± 26 W). Pre- and postexercise twitch responses from the quadriceps to the electrical stimulation of the femoral nerve and magnetic stimulation of the motor cortex were recorded to assess neuromuscular and corticospinal function, respectively.

Results: Exercise time was 3.14 ± 0.59, 11.11 ± 1.86, and 42.14 ± 9.09 min for S+, S-, and RCP, respectively. All trials resulted in similar reductions in maximum voluntary force (P = 0.61). However, the degree of peripheral fatigue varied in an intensity-dependent manner, with greater reductions in potentiated twitch force after S+ (-33% ± 9%) compared with both S- (-16% ± 9%, P < 0.001) and RCP trials (-11% ± 9%, P < 0.001) and greater after S- compared with RCP (P < 0.05). For central fatigue, this trend was reversed, with smaller reductions in voluntary activation after S+ compared with RCP (-2.7% ± 2.2% vs –9.0% ± 4.7%, P < 0.01).

Conclusion: These data suggest the magnitude of peripheral and central fatigue after locomotor cycling exercise is exacerbated with exercise intensity and duration, respectively.

Item Type: Article
Uncontrolled Keywords: Central, locomotor exercise, muscle, peripheral, voluntary activation, transcranial magnetic stimulation
Subjects: C600 Sports Science
Department: Faculties > Health and Life Sciences > Sport, Exercise and Rehabilitation
Depositing User: Nicola King
Date Deposited: 13 Jun 2016 14:29
Last Modified: 06 Nov 2017 13:38

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