Cigarette smoking slows the on- and the off- cardiorespiratory and gas-exchange kinetics during moderate exercise in young, physically active adults

Cigarette smoking (CS) impact on cardiopulmonary function has been extensively investigated on sedentary, middle-aged smokers (SMK) with pulmonary disease, but not on young SMK with high fitness level. This study evaluated the cardiopulmonary and gas-exchange kinetics during and after moderate exercise in young, physically active SM without known diseases. Ten SMK (age: 21 ± 2 year., body mass: 78 ± 6 kg; stature: 1.79 ± 0.07 m; 12 ± 5 cigarette/day for 6 ± 2 year.; mean ± SD) and twelve non-smokers (CTRL; age: 24 ± 3 year., body mass: 78 ± 9 kg; stature: 1.80 ± 0.08 m) matched also for exercise habits performed an incremental cycloergometric test to assess maximum pulmonary oxygen uptake ( $$\:{\dot{\text{V}}}_{{\text{O}}_{2}\:\text{m}\text{a}\text{x}}$$ ) and first ventilatory threshold (VT1). After pulmonary evaluation, participants performed four 6-min moderate-intensity tests at 90% VT1. The time constant (τ) of the on- and off-phases were determined for expiratory ventilation ( $$\:{\dot{\text{V}}}_{\text{E}}$$ ), $$\:{\dot{\text{V}}}_{{\text{O}}_{2}}$$ , heart rate (fH) and cardiac output ( $$\:\dot{\text{Q}}$$ ). Despite similar static lung volumes, SMK exhibited lower peak expiratory flow (-21%; P = 0.009) and maximal voluntary ventilation (-12%; P = 0.008). SMK had lower $$\:{\dot{\text{V}}}_{{\text{O}}_{2\:\text{m}\text{a}\text{x}}}$$ (3657 ± 325 vs. 3397 ± 316 ml∙min− 1 for CTRL and SMK, respectively; P = 0.009) and mechanical power at VT1 (201 ± 26 vs. 185 ± 16 W for CTRL and SMK respectively; P = 0.041). In on-phase, SMK demonstrated longer τ in $$\:\dot{\text{Q}}$$ (+ 22%; P = 0.032), $$\:{f}_{\text{H}}$$ (+ 56%; P = 0.005), $$\:{\dot{\text{V}}}_{{\text{O}}_{2}}$$ (+ 41%; P = 0.032), $$\:{\dot{\text{V}}}_{\text{E}}$$ (+ 47%; P = 0.007) and. In off-phase, τ in SMK was lengthened for $$\:\dot{\text{Q}}$$ (+ 51%; P = 0.041), $$\:{f}_{\text{H}}$$ (+ 42%; P = 0.022), $$\:{\dot{\text{V}}}_{{\text{O}}_{2}}$$ (+ 20%; P = 0.002) and $$\:{\dot{\text{V}}}_{\text{E}}$$ (+ 42%; P = 0.018). CS slowed cardiopulmonary and gas-exchange kinetics at moderate exercise even in young individuals with short smoking history.