【摘要】 目的：基于血氧水平依赖功能磁共振成像（functional magnetic resonance imaging-blood oxygen level dependent,fMRI-BOLD）技术，探讨4周低氧持续训练对小腿骨骼肌抗缺氧能力的影响，从无创在体骨骼肌视角解析低氧训练提升有氧耐力的生理机制。方法：招募26名具有耐力训练经历的健康成年男性，随机分为低氧训练组（n=13）和常氧训练组（n=13）。低氧训练组在模拟海拔2500 m（FiO₂=14.8%～15.3%）环境下运动，常氧训练组在常规环境（FiO₂=20.3%～20.8%）中进行训练。两组均进行为期4周、每周3次、每次45 min的跑台训练，强度统一设定为个体通气无氧阈跑速。训练前后分别进行3km跑成绩测试（3 kmTT）；采用递增负荷测试评估受试者最大摄氧量(VO_2max)和通气无氧阈占最大摄氧量比值[无氧阈（ventilatory anaerobic threshold,VAT）/VO_2max]；基于fMRI-BOLD技术测量胫骨前肌、腓骨长肌、比目鱼肌和腓肠肌最小T信号强度（）相对于加压缺血前的百分比变化（Min-I）、最大T相对于加压缺血前的百分比变化（Max-H）和达到最大值的时间（TTP）。采用双因素（时间×分组）重复测量方差分析评价训练效果，并利用Pearson相关分析探讨骨骼肌氧合指标变化与有氧耐力表现提升之间的关联。结果：1)与训练前相比，训练后低氧训练组3 kmTT时间显著缩短（P<0.01）,VAT/VO_2max显著升高（P<0.01）；训练后低氧训练组3 kmTT时间显著短于常氧训练组（P<0.05）。2)与训练前相比，训练后低氧训练组胫骨前肌、腓骨长肌、比目鱼肌和腓肠肌的骨骼肌氧合指标均发生不同程度改善，其中胫骨前肌、腓骨长肌、比目鱼肌和腓肠肌的Min-I显著降低（P<0.05）、Max-H显著升高（P<0.01）、TTP显著缩短（P<0.05）；与训练前相比，训练后常氧训练组腓骨长肌、比目鱼肌和腓肠肌的Min-I显著降低（P<0.05），比目鱼肌和腓肠肌的TTP显著降低（P<0.05）。训练后，低氧训练组胫骨前肌、比目鱼肌和腓肠肌Min-I显著低于常氧训练组（P<0.05），胫骨前肌、比目鱼肌和腓肠肌Max-H显著高于常氧训练组（P<0.01），且胫骨前肌TTP显著低于常氧训练组（P<0.05）。3)低氧训练组3 kmTT成绩提升与胫骨前肌、比目鱼肌和腓肠肌的ΔMin-I呈显著正相关（r=0.87、0.91、0.84,P<0.01），与胫骨前肌、比目鱼肌和腓肠肌的ΔMax-H亦呈显著正相关（r=0.79、0.88、0.84,P<0.01）。结论：4周低氧持续训练可显著提升有氧耐力运动表现，其作用可能与小腿关键肌群骨骼肌氧合能力增强有关。低氧持续训练可改善骨骼肌缺血-再灌注过程中的氧合动力学和血流恢复特征，提高氧气转运与利用效率，从而增强骨骼肌抗缺氧能力。更多还原

【Abstract】 Objective To explore the effect of 4-week continuous hypoxic training on the hypoxia tolerance of calf skeletal muscles using blood oxygen level-dependent functional magnetic resonance imaging（fMRI-BOLD）,and to observe its physiological mechanism by which hypoxic training enhances aerobic endurance from the perspective of noninvasive in vivo skeletal muscle assessment. Methods Twenty-six healthy adult men with endurance training experience were recruited and randomly assigned to a hypoxic training group（n=13） and a normoxic training group（n=13）. The hypoxic training group trained under simulated altitude conditions of 2500 m（FiO₂=14.8%～15.3%）,whereas the normoxic training group underwent training in normoxic conditions（FiO₂=20.3%～20.8%）. Both groups conducted treadmill training for 4 weeks,3 times per week,45 min per session,at an intensity corresponding to each individual’s ventilatory anaerobic threshold running speed. Before and after the intervention,a 3-km time trial（3 kmTT） was performed. Moreover,an incremental exercise test was employed to assess maximal oxygen uptake(VO_2max) and the ratio of ventilatory anaerobic threshold to maximal oxygen uptake(VAT/VO_2max). Meanwhile,based on f MRI-BOLD,the percentage change in minimum T weighted signal intensity（ relative to the pre-occlusion baseline（Min-I）,the percentage change in maximum T relative to the pre-occlusion baseline（Max-H）,and the time to peak signal（TTP）were measured in the tibialis anterior,peroneus longus,soleus,and gastrocnemius muscles. Then,a two-way repeated-measures analysis of variance（time × group） was employed to evaluate the training effect,and Pearson correlation analysis was performed to examine the associations between changes in skeletal muscle oxygenation indices and improvements in aerobic endurance performance. Results 1） After the intervention,the hypoxic training group showed a significant decrease in 3 kmTT time（P<0.01） and a significant increase in VAT/VO_2max（P<0.01）. After training,3 kmTT time was significantly shorter in the hypoxic training group than in the normoxic training group（P<0.05）. 2) After training,skeletal muscle oxygenation indices in the hypoxic training group improved to varying degrees in the tibialis anterior, peroneus longus, soleus, and gastrocnemius muscles. Specifically, Min-I decreased significantly in the tibialis anterior, peroneus longus, soleus, and gastrocnemius（P<0.01）,while Max-H increased significantly in the tibialis anterior,peroneus longus,soleus,and gastrocnemius（P<0.01）,with TTP shortened in the tibialis anterior,peroneus longus,soleus,and gastrocnemius（P<0.05）. After training,Min-I in the tibialis anterior,soleus,and gastrocnemius was significantly lower in the hypoxic training group than in the normoxic training group（P<0.05）, whereas Max-H in the tibialis anterior, soleus, and gastrocnemius was significantly higher（P<0.01）, with TTP in the tibialis anterior being significantly shorter（P<0.05）. 3) Improvements in 3 kmTT performance in the hypoxic training group were significantly positively correlated with ΔMin-I in the tibialis anterior,soleus,and gastrocnemius（r=0.87,0.91,and 0.84,respectively; P<0.01）,and were also significantly and positively correlated with ΔMax-H in the tibialis anterior,soleus,and gastrocnemius（r=0.79,0.88,and 0.84,respectively; P<0.01）. Conclusion Four-week continuous hypoxic training can significantly improve aerobic endurance performance,and this effect may be associated with enhanced skeletal muscle oxygenation capacity in key calf muscle groups. Therefore,continuous hypoxic training may improve oxygenation kinetics and blood flow recovery characteristics during skeletal muscle ischemia-reperfusion, thereby increasing oxygen transport and utilization efficiency and ultimately enhancing skeletal muscle hypoxia tolerance.更多还原