Cigarette Smoking Effects On Cardiorespiratory Response To Exercise And Recovery In Young Active Adults

Cigarette smoking is the leading preventable cause of mortality. It induces systemic changes that detrimentally impact cardiovascular and pulmonary function. Indeed, nicotine stimulates the sympathetic nervous system, tar impairs O2 diffusion, and carbon monoxide reduces O2 transport and extraction. Although these abnormalities are reported in sedentary, middle-aged smokers (SM) with pulmonary disease, few and controversial studies focused on young SM without any comorbidities. PURPOSE: To assess possible differences in pulmonary O2 uptake (V’O2), expiratory ventilation (V’E) and heart rate (fH) response during and after a maximum incremental test between young active SM and non-smokers (CTRL). METHODS: After evaluating the pulmonary function by spirometry, 12 physically active SM (age: 22 ± 2 yr.; body mass: 75 ± 8 kg; stature: 1.78 ± 0.06 m; 12 ± 4 cigarette/day for 6 ± 2 years; mean ± SD) and 12 age-matched CTRL (age: 23 ± 1 yr.; body mass: 76 ± 8 kg; stature: 1.79 ± 0.08 m) performed a maximal incremental step test (25 W/2 min) on a cycle ergometer until exhaustion, followed by 5-min active recovery at 30 W (30 rpm). V’E, V’O2 and fH responses as well as lactate concentration were assessed during and after the test. A mono-exponential function determined the time constant (τ) of recovery kinetics. RESULTS: Despite similar spirometric static volumes, SM reported lower peak expiratory flow (-23%; P < 0.01) and maximal voluntary ventilation (-10%; P = 0.01). SM exhibited earlier ventilatory (P < 0.01) and lactate thresholds (P = 0.01). At peak exercise, SM had lower V’O2 (44 ± 5 vs 48 ± 5 ml·min-1·kg-1 for SM and CTRL, respectively; P = 0.02), mechanical power (256 ± 30 vs 288 ± 29 W for SM and CTRL, respectively; P = 0.02) and V’E (126 ± 12 vs 139 ± 15 l·min-1 for SM and CTRL, respectively; P = 0.02). During the recovery phase, SM showed longer τ in V’O2 (68 ± 23 vs 45 ± 12 s SM and CTRL, respectively; P < 0.01), V’E (126 ± 10 vs 140 ± 13 s, respectively; P = 0.03) and fH (105 ± 28 vs 87 ± 10 s, respectively; P = 0.02). CONCLUSION: Cigarette smoking adversely affects cardiorespiratory and metabolic responses during and after maximal exercise, thereby elevating cardiovascular risk for SM. This holds true despite their young age and physical fitness level. University of Milan, Linea 2