Author(s): BORRELLI, M., MOTALLI, A., DORIA, C., TONINELLI, N., LIMONTA, E., GALASSO, L., LONGO, S., CORATELLA, G., CÈ, E., RAMPICHINI, S., ESPOSITO, F., Institution: UNIVERSITÀ DEGLI STUDI DI MILANO, Country: ITALY, Abstract-ID: 1549

INTRODUCTION:
Cigarette smoking (CS) is the leading preventable cause of death, causing systemic changes that harmfully impact cardiovascular and pulmonary function at rest and during exercise. Indeed, nicotine overstimulates the sympathetic nervous system, tar alters O2 diffusion, and carbon monoxide reduces O2 transport and extraction (1). Although these effects are well-established in sedentary, middle-aged smokers (SM) with pulmonary disease, limited and controversial studies have focused on young SM without comorbidities (2). Hence, the aim of this study was to evaluate the cardiorespiratory and metabolic kinetics during moderate exercise in young, physically active SM without known lung or cardiovascular disease. It was hypothesized that, despite their brief smoking history and good fitness level, which could mitigate the negative CS effects, SM would exhibit slower kinetics, due to early alterations in oxidative stress, autonomic response and O2 delivery.
METHODS:
The study enrolled 10 physically active 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 (25W/2 min) on a cycle ergometer to determine the maximum pulmonary oxygen uptake (V’O2max). After pulmonary evaluation, participants performed four 6-min square wave tests at 90% first ventilatory threshold VT1 (3). The time constant (t) for expiratory ventilation (V’E), VO2, heart rate (fH) and cardiac output (Q’) during the increasing (on-phase) and decreasing (off-phase) transients was assessed using a mono-exponential model.
RESULTS:
Static lung volumes were similar between SM and CTRL; however, SM had lower peak expiratory flow (-21%; P=0.004) and maximal voluntary ventilation (-12%; P=0.004). Additionally, SM had 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, t in SM was longer for fH (+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 t for fH (+37%; P=0.014), V’O2 (+20%; P=0.004), V’E (+35%; P=0.045) and Q’ (+51%; P=0.020).
CONCLUSION:
These results demonstrate that CS negatively impacts cardiorespiratory and metabolic kinetics at moderate exercise, thereby elevating cardiovascular risk in SM, despite their young age, relative short smoking history and physical fitness level.

REFERENCES:
1. Muller et al. Front Physiol. 2019
2. Borrelli et al. Med Sci Sports Exerc. 2024
3. Murias et al. Am J Physiol Regul Integr Comp Physiol. 2011