The effects of pain and fatigue on regulation of exercise performance

长期以来，人们一直认为，在剧烈运动期间感觉到的疲劳和疼痛与运动耐量的短暂降低有关。这些感知反应已被归因于几个生理和心理因素的相互作用，其中机械和代谢敏感的III/IV组肌肉传入的激活是公认的。除了疲劳和疼痛的有意识感觉之外，III/IV组感觉传入的激活已被证明对于神经肌肉（NM）和心血管（CV）反应的调节是至关重要的。然而，很少有人知道如何NM，CV和知觉反应整合，以确定运动耐量。 为了研究第III/IV组感觉反馈反应对运动耐量的影响，以前的文献主要集中在药理学试剂的应用（例如，阿司匹林和咖啡因）;然而，较少关注运动对疲劳和疼痛调节的潜在镇痛作用。事实上，暴露于接近最大疼痛耐受力的锻炼，如高强度间歇训练（HIIT），已被证明可以减轻对锻炼的感知反应。 因此，我的研究计划的长期目标是探索急性和慢性生理和感知机制如何整合，以确定运动耐量。为实现这一目标，我的近期目标是：1.探讨不同训练背景个体的疼痛耐受性及其与NM、CV和疲劳运动知觉反应的关系：2.研究不同运动干预，特别是高强度间歇训练（HIIT）对决定运动耐受性的急性和慢性生理和知觉反应的影响; 3.采用经颅磁刺激、电刺激和功能性近红外光谱（fNIRS）等神经影像学技术，研究运动干预对中枢神经系统（脑和脊髓）反应的急性和慢性影响。在我的研究计划的实验协议将进行创新的定制横卧自行车测力计，有利于在一秒钟内疲劳后NM评价。NM测量将包括叠加经颅磁刺激和电刺激的一系列最大和次最大等长膝关节伸展（以评估NM性能和皮质脊髓兴奋性/抑制）; CV评估将包括平均动脉压、心率、气体交换和通气;感知反应将包括感知劳累、觉醒、全身疲劳和疼痛的评级。更好地理解NM，CV和运动耐量的知觉决定因素之间的整合，在我的研究计划中提出的一系列横截面和训练研究将产生新的知识，为发展非药理学方法，以提高运动表现。

Fatigue and pain perceived during intensive exercise has long been associated with a transient reduction in exercise tolerance. These perceptual responses have been attributed to an interplay of several physiological and psychological factors among which activation of mechano- and metabo-sensitive group III/IV muscle afferents are well recognized. In addition to conscious sensation of fatigue and pain, activation of group III/IV sensory afferents has been shown to be critical for regulation of neuromuscular (NM) and cardiovascular (CV) responses. However, little is known about how NM, CV, and perceptual responses integrate to determine exercise tolerance. To study the impact of group III/IV sensory feedback responses on exercise tolerance, previous literature has mainly focused on the application of pharmacological agents (e.g., aspirin and caffeine); however, less attention has been paid to potential analgesic effects of exercise on fatigue and pain modulation. Indeed, exposure to exercises approaching the maximal pain tolerance, such as high intensity interval training (HIIT), has been shown to mitigate perceptual responses to exercise. Thus, the long-term objective of my research program is to explore how acute and chronic physiological and perceptual mechanisms integrate to determine exercise tolerance. In striving to meet this objective, my short-term objectives are to: 1.Explore pain tolerance and its relationship with NM, CV and perceptual responses to a fatiguing exercise in individuals with different training backgrounds; 2.Study the effect of different exercise interventions, specifically high intensity interval training (HIIT), on acute and chronic physiological and perceptual responses determining exercise tolerance; 3.Investigate the acute and chronic effects of exercise interventions on central nervous system (brain and spinal cord) responses using transcranial magnetic and electrical stimuli, and neuroimaging techniques such as functional near infrared spectroscopy (fNIRS). Experimental protocols in my research program will be carried out on an innovative custom-built recumbent cycle ergometer that facilitates the post-fatigue NM evaluation within a second. The NM measurements will include a series of maximal and submaximal isometric knee extensions superimposed with transcranial magnetic and electrical stimuli (to assess NM performance and corticospinal excitability/inhibition); CV assessments will include mean arterial pressure, heart rate, gas-exchange and ventilation; and perceptual responses will include rating of perceived exertion, arousal, general fatigue, and pain. Better understanding the integration between NM, CV and perceptual determinants of exercise tolerance throughout a series of cross-sectional and training studies proposed in my research program will generate new knowledge for the development of non-pharmacological methods to improve exercise performance.