Author(s): MOTALLI, A., BORRELLI, M., DORIA, C., TONINELLI, N., LONGO, S., LIMONTA, E., CÈ, E., RAMPICHINI, S., ESPOSITO, F., Institution: UNIVERSITÀ DEGLI STUDI DI MILANO, Country: ITALY, Abstract-ID: 1550

INTRODUCTION:
Cigarette smoking (CS) has a detrimental impact on cardiorespiratory and metabolic response to exercise. Indeed, CS alters the sympathetic drive of the autonomic nervous system, increases airway resistance and oxidative stress, and impairs oxygen delivery (1). It is well-reported a diminished cardiorespiratory fitness in sedentary, middle-aged smokers (SM) with pulmonary disease, index of higher cardiovascular risk. By contrast, limited and controversial studies exist on CS effects in young, physically active SM with a short history of CS (2). Thus, the study aims to investigate the impact of CS on cardiorespiratory and metabolic kinetics during the onset of a square-wave moderate exercise in this population.
METHODS:
Ten SM (age: 22±2 yrs, body mass: 78±6 kg, stature:1.79±0.07 m, 11±5 cigarette/day for 6±2 yrs; mean±SD) and 11 non-smokers (CTRL; age: 23±1 yrs, body mass: 78±8 kg, stature: 1.80±0.09 m) completed a pulmonary function evaluation. Then, they performed an incremental step test to assess cardiorespiratory and metabolic variables at peak exercise and the two ventilatory thresholds. Lastly, participants performed four 6-minute square-wave exercise (90% of the first ventilatory threshold) to assess the kinetics of expiratory ventilation (VE), oxygen uptake (VO2) and heart rate (fH) responses. Breath-by-breath values of all these variables were averaged and then fitted by a bi-exponential function to determine the amplitude (AMP) and the time constant (tau) of the cardiorespiratory and metabolic kinetics.
RESULTS:
Static lung volumes were similar between groups. However, SM showed a reduced peak expiratory flow (8.4±1.8 vs 10.5±1.8 l·s-1, respectively; P=0.01) and lower maximum voluntary ventilation (168±14 vs 191±23 l·min-1; respectively, P=0.01) compared to CTRL. At peak exercise, despite similar VO2 (3384±318 vs 3623±333 ml·min-1; for SM and CTRL, respectively), SM exhibited lower mechanical power output (253±21 vs 278±27 W, respectively; P=0.01) and VE (125±11 vs 139±11 l·min-1, respectively, P=0.02). In addition, SM reached ventilatory threshold earlier than CTRL. During constant moderate exercise, SM displayed prolonged VO2 phase I (tau: 17±9 vs 12±4 s for SM and CTRL, respectively; P=0.03) and reduced phase II amplitude (886±301 vs 1111±295 ml·min-1, for SM and CTRL, respectively; P=0.05). Moreover, SM exhibited a slower fH response during phase II (61±18 vs 48±13 s, respectively; P=0.03).
CONCLUSION:
The longer cardiorespiratory kinetics demonstrate that CS alters the cardiorespiratory and metabolic responses to exercise even in young, asymptomatic SM with a relatively short smoking history.

REFERENCES:
1 - Muller et al. Front Physiol. 2019
2 - Borrelli et al. Med Sci Sports Exerc. 2024