do Nascimento Salvador Paulo Cesar, Schäfer Lisa, Grassi Bruno, Guglielmo Luiz Guilherme Antonacci, Denadai Benedito Sérgio
Physical Effort Laboratory, Sports Center, Federal University of Santa Catarina, Florianopolis, Brazil.
Leonardo da Vinci University/Uniasselvi, Indaial, Brazil.
Front Physiol. 2019 Apr 25;10:471. doi: 10.3389/fphys.2019.00471. eCollection 2019.
A link between muscle fatigue, decreased efficiency and the slow component of oxygen uptake (VOsc) has been suggested. However, a cause-effect relationship remains to be elucidated. Although alterations in VO kinetics after elevated baseline work rate have previously been reported, to date no study has observed the effect on muscle force production (MFP) behavior considering physiological differences between male and female subjects. This study investigated the effect of elevated baseline work rate on the VO kinetics and MFP in 10 male and 10 female healthy subjects. Subjects performed 4 transitions of very-heavy (VH) intensity cycling in a randomized order after unloaded (U-VH) or moderate (M-VH) exercise. Maximal isokinetic efforts (MIE) were performed before and after each condition at two different cadences (60 or 120 rpm). Whereas baseline VO and time constant (τ) were significantly higher in M-VH compared to U-VH, the fundamental amplitude and the VO slow component (VOsc) were significantly lower in M-VH ( < 0.05) in both sexes. Blood lactate concentration ([La]) and rate of perceived exertion (RPE) were not influenced by condition or sex ( > 0.05). The MFP post-exercise was not significantly influenced by condition in both sexes and cadences (Δtorque for males: at 60 rpm in U-VH = 13 ± 10 Nm, in M-VH = 13 ± 9 Nm; at 120 rpm in U-VH = 22 ± 14 Nm, in M-VH = 21 ± 12 Nm; for females: at 120 rpm in U-VH = 10 ± 9 Nm, in M-VH = 12 ± 8 Nm; > 0.05), with the exception that female subjects presented smaller decreases in M-UH at 60 rpm compared to U-VH (11 ± 13 vs. 18 ± 14 Nm, respectively, < 0.05). There was no correlation between the decrease in torque production and VO kinetics parameters ( > 0.05). The alterations in VO kinetics which have been suggested to be linked to changes in motor unit recruitment after elevated baseline work rate did not reflect alterations in MFP and fatigue in both sexes.
肌肉疲劳、效率降低与摄氧量慢成分（VOsc）之间的联系已被提出。然而，因果关系仍有待阐明。尽管此前已有报道称基线工作率升高后VO动力学发生改变，但迄今为止，尚无研究考虑男女受试者的生理差异，观察其对肌肉力量产生（MFP）行为的影响。本研究调查了基线工作率升高对10名男性和10名女性健康受试者的VO动力学和MFP的影响。受试者在无负荷（U-VH）或中等强度（M-VH）运动后，以随机顺序进行4次极重度（VH）强度的骑行转换。在每种条件前后，以两种不同的踏频（60或120转/分钟）进行最大等速肌力测试（MIE）。与U-VH相比，M-VH的基线VO和时间常数（τ）显著更高，而在两种性别中，M-VH的基本振幅和VO慢成分（VOsc）显著更低（P<0.05）。血乳酸浓度（[La]）和主观用力程度（RPE）不受条件或性别的影响（P>0.05）。运动后的MFP在两种性别和踏频下均不受条件的显著影响（男性的扭矩变化：在U-VH中60转/分钟时=13±10牛米，在M-VH中=13±9牛米；在U-VH中120转/分钟时=22±14牛米，在M-VH中=21±12牛米；女性：在U-VH中120转/分钟时=10±9牛米，在M-VH中=12±8牛米；P>0.05），但有一个例外，即与U-VH相比，女性受试者在60转/分钟时M-UH的下降幅度较小（分别为11±13和18±14牛米，P<0.05）。扭矩产生的下降与VO动力学参数之间无相关性（P>0.05）。基线工作率升高后，VO动力学的改变被认为与运动单位募集的变化有关，但并未反映出两种性别中MFP和疲劳的改变。
