Hureau Thomas J, Olivier Nicolas, Millet Guillaume Y, Meste Olivier, Blain Gregory M
University of Nice Sophia Antipolis, Toulon, LAMHESS, EA 6309, F-06205, Nice, France University of Lille Nord de France, F-59000, Lille, France; UDSL, EA 4488, F-59790, Ronchin, France.
University of Lille Nord de France, F-59000, Lille, France; UDSL, EA 4488, F-59790, Ronchin, France.
Exp Physiol. 2014 Jul;99(7):951-63. doi: 10.1113/expphysiol.2014.077974. Epub 2014 Apr 11.
We hypothesized that exercise performance is adjusted during repeated sprints in order not to surpass a critical threshold of peripheral fatigue. Twelve men randomly performed three experimental sessions on different days, i.e. one single 10 s all-out sprint and two trials of 10 × 10 s all-out sprints with 30 s of passive recovery in between. One trial was performed in the unfatigued state (CTRL) and one following electrically induced quadriceps muscle fatigue (FTNMES). Peripheral fatigue was quantified by comparing pre- with postexercise changes in potentiated quadriceps twitch force (ΔQtw-pot) evoked by supramaximal magnetic stimulation of the femoral nerve. Central fatigue was estimated by comparing pre- with postexercise voluntary activation of quadriceps motor units. The root mean square (RMS) of the vastus lateralis and vastus medialis EMG normalized to maximal M-wave amplitude (RMS.Mmax (-1)) was also calculated during sprints. Compared with CTRL condition, pre-existing quadriceps muscle fatigue in FTNMES (ΔQtw-pot = -29 ± 4%) resulted in a significant (P < 0.05) reduction in power output (-4.0 ± 0.9%) associated with a reduction in RMS.Mmax (-1). However, ΔQtw-pot postsprints decreased by 51% in both conditions, indicating that the level of peripheral fatigue was identical and independent of the degree of pre-existing fatigue. Our findings show that power output and cycling EMG are adjusted during exercise in order to limit the development of peripheral fatigue beyond a constant threshold. We hypothesize that the contribution of peripheral fatigue to exercise limitation involves a reduction in central motor drive in addition to the impairment in muscular function.
我们假设，在重复冲刺过程中，运动表现会进行调整，以避免超过外周疲劳的临界阈值。12名男性在不同日期随机进行了三个实验环节，即一次10秒全力冲刺，以及两次10×10秒全力冲刺，两次冲刺之间有30秒的被动恢复时间。一次实验在未疲劳状态下进行（CTRL），另一次在电刺激股四头肌导致疲劳后进行（FTNMES）。通过比较运动前和运动后股神经超强磁刺激诱发的股四头肌增强抽搐力（ΔQtw-pot）的变化来量化外周疲劳。通过比较运动前和运动后股四头肌运动单位的自主激活来评估中枢疲劳。在冲刺过程中还计算了股外侧肌和股内侧肌肌电图的均方根（RMS），并将其归一化到最大M波振幅（RMS.Mmax (-1)）。与CTRL状态相比，FTNMES中预先存在的股四头肌疲劳（ΔQtw-pot = -29 ± 4%）导致功率输出显著降低（P < 0.05）（-4.0 ± 0.9%），同时RMS.Mmax (-1)也降低。然而，两种状态下冲刺后的ΔQtw-pot均下降了51%，这表明外周疲劳程度相同，且与预先存在的疲劳程度无关。我们的研究结果表明，在运动过程中功率输出和骑行肌电图会进行调整，以限制外周疲劳超过恒定阈值的发展。我们推测，外周疲劳对运动限制的作用除了肌肉功能受损外，还涉及中枢运动驱动的降低。
