Background: Smokers without airflow obstruction have reduced exercise capacity, but the underlying physiological mechanisms are not fully understood. Aim: To compare quadriceps function assessed using non-volitional measures, and ventilatory requirements during exercise, between smokers without airway obstruction and never-smoker controls. Study Design and Methods: Adult smokers (n=20) and never-smoker controls (n=16) aged 25-50 years with normal spirometry, underwent incremental cycle cardiopulmonary exercise testing to exhaustion with measurement of symptoms and dynamic lung volumes. Quadriceps strength and endurance were assessed non-volitionally using single and repetitive magnetic stimulation. Quadriceps bulk was assessed using ultrasound, as rectus-femoris cross-sectional area (Q_RF-CSA). Physical activity level was quantified using the SenseWear^TM armband worn for 5 days. Results: Smokers had lower peak exercise workload, peak oxygen consumption and anaerobic threshold (AT) compared to controls (170+46 vs. 256+57 W; 2.20 ±0.56 vs. 3.18 ±0.72 L/min; 1.38±0.33 vs. 2.09±0.7 L/min, respectively; p<0.01 for all). Quadriceps endurance was lower in smokers (D force-time integral 54.9±14.7% vs. 40.4±14.7%; p=0.007), but physical activity, quadriceps strength and bulk were similar between groups. Smokers displayed higher ventilation (120W: 52.6±11.8 vs. 40.7±6.0 L/min; p<0.001), decreased ventilatory efficiency (higher ⩒_E/⩒CO₂) and were more breathless with greater leg fatigue at iso-workloads and iso-ventilation levels compared to never-smoker controls. Smokers showed no mechanical constraints on tidal volume expansion during exercise or ventilatory limitation at peak exercise. Conclusion: Adult smokers without airflow obstruction have reduced skeletal muscle endurance and ventilatory efficiency compared to never-smoker controls, despite similar daily physical activity levels, which contributed to reduced peak exercise capacity.

中文翻译：

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在没有气流阻塞的成年吸烟者运动期间降低骨骼肌耐力和通风效率

背景：没有气流阻塞的吸烟者的运动能力下降，但其潜在的生理机制尚未完全了解。目的：比较没有气道阻塞和从未吸烟者控制的吸烟者使用非自愿措施评估的股四头肌功能和运动过程中的通气要求。研究设计和方法：年龄在25至50岁之间，肺活量正常的成年吸烟者（n = 20）和从不吸烟的对照者（n = 16），进行了递增循环的心肺运动测试，以测量体力和肺活量来衰竭。股四头肌的强度和耐力使用单次和重复性磁刺激进行非自愿性评估。使用超声评估股四头肌的体积，作为股直肌截面积（Q _RF）-CSA）。使用佩戴了5天的SenseWear ^TM袖带对身体活动水平进行定量。结果：与对照组相比，吸烟者的峰值运动负荷，峰值耗氧量和无氧阈值（AT）更低（170 + 46 vs.256 + 57 W; 2.20±0.56 vs. 3.18±0.72 L / min; 1.38±0.33 vs. 2.09分别为±0.7 L / min；所有p <0.01）。吸烟者的股四头肌耐力较低（D力-时间积分为54.9±14.7％和40.4±14.7％； p = 0.007），但两组之间的体育锻炼，股四头肌力量和体型相似。吸烟者显示更高通气（120W：52.6±11.8对比40.7±6.0 L /分钟; P <0.001），降低通气效率（较高⩒ _ë /⩒CO ₂），与从不吸烟的控制者相比，在等负荷工作量和同等通风水平下，人们的呼吸更加舒畅，腿部疲劳加剧。吸烟者在运动期间没有表现出机械上的限制潮气量的限制，也没有在高峰运动时限制通风的限制。结论：与不吸烟的对照组相比，没有气流阻塞的成年吸烟者降低了骨骼肌的耐力和通气效率，尽管每天的体育活动水平相似，这导致峰值运动能力下降。