过度训练导致机体健康损害的关键内在机制探讨

The Exquisite Intrinsic Mechanisms of Adverse Health Effects Caused by Overtraining

过度训练是训练负荷与身体机能不匹配且恢复期安排不合理,引起疲劳连续过度积累且超过机体所能承受的“度”,进而诱发的一系列功能紊乱或病理状态,是训练与恢复、运动与运动能力、应激与应激耐受性之间的一种失衡状态。过度训练可引起运动表现下降、食欲减退、体重降低、肌肉疲劳损伤与功能障碍、肌肉萎缩、肌糖原耗竭、肝脏/心肌脂肪沉积、葡萄糖耐受力下降、心脏病理性肥大、运动性心律失常、心肌纤维化和认知功能减退等多种显性改变或病理重塑,但其内在机制却不甚明晰。近年来,细胞分子信号调控理论的逐渐丰富与完善,为研究过度训练导致健康损害的内在机制提供了新的解释范式。本文在传统解释机制基础上,基于细胞分子信号调控理论,从氧化应激、线粒体质量控制、炎症反应、内质网应激和细胞凋亡等视角,对过度训练导致机体健康受损的内在机理进行深入解析,以期为运动员及运动参与者进行科学运动训练、提高训练效果、延长运动寿命、保持身心健康提供重要参考依据。

Overtraining is a condition characterized by various functional disorders or pathological states caused by continuous fatigue,which occurs after a persisting imbalance between training-related load and physical function and recovery.Generally speaking,it’s a state of imbalance between training and recovery,exercise and exercise performance,and stress and stress tolerance.Overtraining can cause various phenotypic changes or pathological remodeling,such as decreased skeletal muscle strength and exhaustive exercise endurance,skeletal muscle fatigue damage and dysfunction,skeletal muscle atrophy and loss,skeletal muscle glycogen depletion,skeletal muscle soreness and stiffness,skeletal muscle glucose intolerance,inattention,memory decline,anxiety,depression,abnormal emotions and behaviors,sleep disorders,cognitive function impairment,poor appetite,weight loss,liver/heart fat deposition,compensatory increase of liver/heart insulin signaling and glycogen storage,cardiac pathological hypertrophy,exercise-induced arrhythmias,myocardial fibrosis,ectopic and visceral fat deposition,and increased risk of injury.Unfortunately,its underlying mechanism is largely unclear.Recently,the enrichment of molecular and cellular signal pathway theory offers us a new explanatory paradigm for revealing its internal mechanisms.Based on the traditional explanation mechanisms and molecular and cellular signal pathway theory,we thoroughly analyzed the key mechanisms of health damage caused by overtraining from the perspective of oxidative stress,mitochondrial quality control disorder,inflammatory response,endoplasmic reticulum stress,cell apoptosis,and so forth.Specifically,overtraining-induced excessive reactive oxygen species(ROS)leads to serious oxidative stress damage in organisms at least via depressing Kelch like ECH associated protein 1(Keap1)/nuclear factor erythroid-2-related factor(Nrf2)/antioxidant response element(ARE)antioxidant pathway and activating p38 mitogen-activated protein kinase(p38 MAPK)signaling pathway.Overtraining induces mitochondrial quality control disorder and mitochondrial dysfunction,and thus triggers health impairment through inhibiting mitochondrial biogenesis and fusion,stimulating mitochondrial fission,and over-activating autophagy/mitophagy.Overtraining can also produce muscle,skeletal and joint trauma,then circulating monocytes are abundantly activated by injury-related cytokines,and in turn generate large quantities of proinflammatory IL-1β,IL-6,TNF‑α,causing systemic inflammation and inflammatory health injury.Overtraining induces excessive pathological endoplasmic reticulum stress(ERS)and severe health damage via PERK-eIF2α,IRE1α-XBP1 and ATF6 pathways which activated by proinflammatory signals.Overtraining also induces excessive apoptosis and harmful health consequences via Bax/Bcl2-Caspase 3-mediated mitoptosis which activated by oxidative stress and inflammation or even CHOP and Caspase 12-dependent ERS apoptosis.Nonetheless,it should be importantly emphasized that oxidative stress and inflammation are the central and preemptive mechanisms of overtraining and its health damage.Although the efficient strategies for preventing and controlling overtraining are scientifically and reasonably arranging and planning training intensity,training volume,and recovery period,as well as accurately assessing and monitoring physical function status in the early stage,yet various anti-inflammatory,anti-oxidant,anti-apoptotic,or anti-aging drugs such as curcumin,astaxanthin,oligomeric proanthocyanidins,silibinin,hibiscus sabdariffa,dasatinib,quercetin,hydroxytyrosol,complex probiotics,astragalus polysaccharides,semaglutide and fasudil also have an irreplaceable positive effect on preventing overtraining and its relevant health damage via depressing oxidative stress,mitochondrial quality control disorder,proinflammatory signals,endoplasmic reticulum stress,apoptosis and so on.We hope that this review can help us further grasp the features,mechanisms and regularity of overtraining,and provide an important reference for athletes and sports fan to conduct scientific training,improve training effectiveness,extend exercise lifespan,and promote physical and mental health.