1Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, UNITED KINGDOM; and 2Water Research Group, School of Environmental Sciences and Development, Northwest University, Potchefstroom, SOUTH AFRICA.
Med Sci Sports Exerc. 2016 Sep;48(9):1751-60. doi: 10.1249/MSS.0000000000000950.
We tested the hypothesis that central and peripheral fatigue after constant-load cycling exercise would vary with exercise intensity and duration.
Twelve well-trained male cyclists (V˙O2max, 4.49 ± 0.35 L·min) 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.
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).
These data suggest the magnitude of peripheral and central fatigue after locomotor cycling exercise is exacerbated with exercise intensity and duration, respectively.
我们检验了这样一个假设，即在等负荷踏车运动后，中枢和外周疲劳会因运动强度和持续时间而有所不同。
12 名训练有素的男性自行车运动员（最大摄氧量为 4.49±0.35L·min-1），采用随机交叉设计，在三个恒定负荷踏车试验中完成了耐受极限试验。根据初步斜坡试验的呼吸反应，设定运动强度，以产生与剧烈和重度运动域中的运动一致的心肺代谢反应：1）在最大功率时（S+，379±31W），2）在呼吸交换阈和最大摄氧量之间的差值的 60%（S-，305±23W），3）在呼吸补偿点（RCP，254±26W）。在股神经电刺激和运动皮层磁刺激前后，记录股四头肌的抽搐反应，以分别评估神经肌肉和皮质脊髓功能。
S+、S-和 RCP 的运动时间分别为 3.14±0.59、11.11±1.86和 42.14±9.09min。所有试验均导致最大自愿力的相似降低（P=0.61）。然而，外周疲劳的程度以强度依赖性的方式变化，与 S-（-16%±9%，P<0.001）和 RCP（-11%±9%，P<0.001）相比，S+后增强的抽搐力降低更大，与 RCP 相比，S-后的降低更大（P<0.05）。对于中枢疲劳，这种趋势相反，与 RCP 相比，S+后自愿激活的降低较小（-2.7%±2.2%对-9.0%±4.7%，P<0.01）。
这些数据表明，运动强度和持续时间分别导致运动后外周和中枢疲劳的程度加剧。
