C. M. Spengler: Exercise Physiology Lab, ETH Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
Exp Physiol. 2013 Dec;98(12):1705-17. doi: 10.1113/expphysiol.2013.073635. Epub 2013 Sep 6.
Inspiratory muscle fatigue (IMF) is suggested to compromise exercise performance, possibly via a respiratory muscle metaboreflex that impairs blood flow to working muscles, thereby accelerating the development of fatigue in these muscles. Cycling with IMF has also been associated with an excess ventilatory response, which could per se impair performance. Therefore, the present study investigated whether prior-induced IMF would affect subsequent cycling performance via increased quadriceps muscle fatigue alone and whether fatigue-induced excess ventilation would contribute to this impairment. Fourteen healthy male subjects (peak oxygen uptake, 57.0 ± 5.5 ml min(-1) kg(-1)) cycled to exhaustion at 85% of their maximal work output with prior-induced IMF (PF-EX) and without prior-induced IMF (C-EX). Subjects then cycled twice for the duration of PF-EX but without prior IMF, once with spontaneous breathing (C-ISO) and once with breathing coached to match PF-EX ventilation (MATCH-ISO). Inspiratory muscle (P(tw)) and quadriceps muscle contractility (Q(tw)) was assessed via magnetic nerve stimulation before and after exercise. The time to exhaustion in the PF-EX conditions was significantly reduced by 14% compared with C-EX. The reduction in P(tw) and Q(tw) was greater after PF-EX (P(tw), 17.3 ± 9.7%; Q(tw), 32.0 ± 10.8%) than after MATCH-ISO (P(tw), 10.8 ± 10.3%; Q(tw), 23.3 ± 15.2%; P < 0.05), which may explain the increased perception of exertion and earlier task failure with prior-induced IMF. The augmented ventilatory drive had no effect on reductions in P(tw) and Q(tw) after MATCH-ISO compared with C-ISO. Thus, prior-induced IMF reduces exercise performance, probably as a result of the increased quadriceps muscle fatigue and thus greater perception of exertion independent of the excess respiratory drive when cycling with fatigued inspiratory muscles.
吸气肌疲劳（IMF）被认为会影响运动表现，这可能是通过呼吸肌代谢反射来实现的，该反射会损害向工作肌肉的血流，从而加速这些肌肉的疲劳发展。IMF 下的踏车运动也与过度通气反应有关，这本身可能会损害运动表现。因此，本研究旨在探究先前诱导的 IMF 是否会通过单纯增加股四头肌疲劳来影响随后的踏车运动表现，以及是否疲劳诱导的过度通气会导致这种损害。14 名健康男性（峰值摄氧量，57.0 ± 5.5 ml min(-1) kg(-1)) 在 85%最大输出功率下进行踏车运动，一组在先前诱导的 IMF 下（PF-EX），另一组在没有先前诱导的 IMF 下（C-EX）。然后，受试者在没有先前 IMF 的情况下进行了两次 PF-EX 持续时间的踏车运动，一次是自发性呼吸（C-ISO），一次是呼吸教练与 PF-EX 通气相匹配（MATCH-ISO）。在运动前后，通过磁神经刺激评估吸气肌（P(tw)）和股四头肌收缩力（Q(tw)）。在 PF-EX 条件下，运动至力竭的时间比 C-EX 减少了 14%。与 MATCH-ISO 相比，PF-EX 后 P(tw)（17.3 ± 9.7%）和 Q(tw)（32.0 ± 10.8%）的下降幅度更大，而与 C-ISO 相比，PF-EX 后 P(tw)（10.8 ± 10.3%）和 Q(tw)（23.3 ± 15.2%）的下降幅度更大（P < 0.05），这可能解释了先前 IMF 诱导后运动感知的增加和任务更早失败。与 C-ISO 相比，在 MATCH-ISO 后，增强的通气驱动对 P(tw)和 Q(tw)的下降没有影响。因此，先前诱导的 IMF 降低了运动表现，这可能是由于股四头肌疲劳增加，以及在疲劳吸气肌下踏车时，与过度呼吸驱动无关的运动感知增加所致。
