Faculty of Kinesiology, University of Calgary, Calgary, Canada.
Department of Kinesiology, University of Grenoble Alpes, Grenoble, France.
J Appl Physiol (1985). 2021 Jun 1;130(6):1879-1892. doi: 10.1152/japplphysiol.00892.2020. Epub 2021 Apr 29.
Neuromuscular fatigue (NMF) and exercise performance are affected by exercise intensity and sex differences. However, whether slight changes in power output (PO) below and above the maximal lactate steady state (MLSS) impact NMF and subsequent performance (time to task failure, TTF) is unknown. This study compared NMF and TTF in females and males in response to exercise performed at MLSS, 10 W below (MLSS) and above (MLSS). Twenty participants (9 females) performed three 30-min constant-PO exercise bouts followed (1-min delay) by a TTF at 80% of the peak-PO. NMF was characterized by isometric maximal voluntary contractions (IMVC) and femoral nerve electrical stimulation of knee extensors [e.g., peak torque of potentiated high-frequency (Db100) and single twitch (TwPt)] before and immediately after the constant-PO and TTF bouts. IMVC declined less after MLSS (-18 ± 10%) compared to MLSS (-26 ± 14%) and MLSS (-31 ± 11%; all < 0.05), and the Db100 decline was greater after MLSS (-24 ± 14%) compared to the other intensities (MLSS: -15 ± 9%; MLSS: -18 ± 11%; all < 0.05). Females showed smaller reductions, relative to baseline, in IMVC and TwPt compared to males after constant-PO bouts (all < 0.05), this difference being not dependent on intensity. TTF was negatively impacted by increasing the PO in the constant-PO ( < 0.001), with no differences in end-exercise NMF ( > 0.05). Slight manipulations in PO around MLSS elicited great changes in the reduction of maximal voluntary force and impairments in contractile function. Although NMF was lower in females compared to males, the changes in PO around the MLSS impacted both sexes similarly. It is unknown whether minimum changes in power output (PO) below and above the maximal lactate steady state (MLSS) affect neuromuscular fatigue (NMF) development in females and males. The present data showed that a decrease or increase of 10 W in PO in relation to MLSS elicited lower and greater impairments in contractile function, respectively. Even though females had less of an overall decline in NMF than males, similar exercise intensity-dependent response occurred independently of sex.
神经肌肉疲劳 (NMF) 和运动表现受运动强度和性别差异的影响。然而，在最大乳酸稳态 (MLSS) 以下和以上的功率输出 (PO) 略有变化是否会影响 NMF 以及随后的表现 (任务失败时间，TTF) 尚不清楚。本研究比较了女性和男性在 MLSS、MLSS 以下 (MLSS) 和以上 (MLSS) 时的 NMF 和 TTF。20 名参与者（9 名女性）进行了三次 30 分钟的恒定 PO 运动，随后（1 分钟延迟）以 80%的峰值 PO 进行 TTF。NMF 通过等长最大自主收缩 (IMVC) 和股神经电刺激膝关节伸肌[例如，增强高频 (Db100) 和单收缩 (TwPt) 的峰值扭矩]进行特征描述。在恒定 PO 和 TTF 回合前后。与 MLSS (-26 ± 14%) 和 MLSS (-31 ± 11%)相比，MLSS 后 IMVC 下降较少 (-18 ± 10%)，Db100 下降较大 (-24 ± 14%)与其他强度相比（MLSS：-15 ± 9%；MLSS：-18 ± 11%；均<0.05）。与男性相比，女性在恒定 PO 后（均<0.05），IMVC 和 TwPt 的相对基线下降较小，这种差异与强度无关。在恒定 PO 中增加 PO 会对 TTF 产生负面影响（<0.001），而在运动结束时的 NMF 没有差异（>0.05）。在 MLSS 周围对 PO 进行轻微的操作会导致最大自主力的降低和收缩功能的损伤发生很大的变化。尽管女性的 NMF 低于男性，但 MLSS 周围 PO 的变化对两性的影响相似。目前尚不清楚在最大乳酸稳态 (MLSS) 以下和以上的功率输出 (PO) 最小变化是否会影响女性和男性的神经肌肉疲劳 (NMF) 发展。本研究数据表明，与 MLSS 相比，PO 降低或增加 10 W 分别会导致收缩功能降低和更大的损伤。尽管女性的 NMF 总体下降幅度小于男性，但运动强度依赖性反应独立于性别而发生。
