Impact Of Cigarette Smoking On The Cardiorespiratory And Metabolic Kinetics Moderate Exercise In Young, Physically Active Adults

Cigarette smoking (CS) is the major preventable cause of mortality, leading to systemic modifications that impair the cardiorespiratory and metabolic response to exercise. Although extensive evidence exists regarding the effects of CS in sedentary, middle-aged smokers (SM) with pulmonary disease, data concerning young, physically active SM remain limited and controversial. Therefore, this study sought to evaluate the cardiorespiratory and metabolic kinetics during moderate exercise in young, physically active SM without known lung or cardiovascular disease. We hypothesized that, despite their age, brief smoking history and good fitness level, which could have counterbalanced the harmful CS effects, SM would exhibit elongated kinetics. This would be a result of early developed alterations in oxidative stress, inflammatory state, autonomic response and O 2 delivery. This study involved 10 SM (age: 21±2 yr., body mass: 78±6 kg; stature: 1.79±0.07 m; 12±5 cigarette/day for 6±2 yr.; mean±SD) and 12 non-smokers (CTRL; age: 24±3 yr., body mass: 78±9 kg; stature: 1.80±0.08 m) matched for age and exercise habits. Participants completed an incremental test on a cycle ergometer to determine the maximum pulmonary oxygen uptake (V'O2max). After pulmonary evaluation, participants performed four 6-min moderate-intensity tests at 90% of the first ventilatory threshold (VT1). Mono-exponential function was applied to assess the time constant (τ) of expiratory ventilation (V'E), V'O2, heart rate ( f H) and cardiac output (Q) during the increasing (on-phase) and decreasing (off-phase) transients. SM had similar static lung volumes compared to CTRL but had lower peak expiratory flow (-21%; P=0.004) and maximal voluntary ventilation (-12%; P=0.004). Moreover, SM exhibited lower V'O2max (3657±325 vs 3397±316 ml·min-1 for CTRL and SM, respectively; P=0.037) and mechanical power at VT1 (201±26 vs 185±16 W for CTRL and SM respectively; P=0.045). During the on-phase, τ in SM was longer for f H (+24%; P=0.006), V'O2 (+40%; P=0.009), V'E (+49%; P=0.018) and Q (+22%; P=0.024). Similarly, during the off-phase SM showed longer τ for f H (+37%; P=0.014), V'O2 (+20%; P=0.004), V'E (+35%; P=0.045) and Q (+51%; P=0.020). These findings demonstrate that CS affects cardiorespiratory and metabolic kinetics at moderate exercise even in young individuals with relatively short smoking history. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.