Exercise Intolerance in Young Physically Active Smokers Compared to Non-Smokers During Sinusoidal Cycling

The impact of cigarette smoking on the cardiorespiratory response to exhaustive exercise remains unclear. This study investigated the smoking effect on exercise tolerance by analyzing the cardiorespiratory and metabolic variables during an exhausting sinusoidal exercise in young physically active smokers (SM) without known cardiovascular and respiratory disease. Eight physically active male SM (22.1 ± 2.2 years; 79.9 ± 4.4 kg; maximum oxygen uptake, ${\dot{V}}_{O_2\max }$ 3385 ± 341 mL·min^-1) and 8 non-smokers (controls, 22.6 ± 1.4 years; 74.3 ± 7.9 kg; ${\dot{V}}_{O_2\max }$ 3623 ± 302 mL·min^-1) performed an exhausting sinusoidal cycling exercise. The work rate varied sinusoidally around a midpoint 50 W below the lactate threshold (LT), with an amplitude of ± 50 W and a 4-min cycle period. Midpoint, amplitude, and time-delay between mechanical and metabolic signals of pulmonary ventilation ( ${\dot{V}}_E$ ), ${\dot{V}}_{O_2}$ , and heart rate (HR) were assessed sinusoid-by-sinusoid, as well as blood lactate ([La^-]) and rate of perceived exertion (RPE). Despite similar LT (199 ± 26 vs. 219 ± 28 W for SM and controls, respectively), SM exhibited a lower time to exhaustion (2461 ± 386 vs. 4512 ± 1359 s for SM and controls, respectively; p = 0.001) than controls. No differences between groups emerged in midpoint, amplitude, and time delays, as well as in [La^-] and RPE. In SM, ${\dot{V}}_{O_2}$ midpoint remained constant, whereas in controls during the last cycle was higher compared to the first one (p = 0.001). In both groups, HR (p < 0.01) and ${\dot{V}}_E$ midpoint increased from the first to the last cycle (p < 0.05). The cigarette smoking-induced exercise intolerance suggests metabolic and ventilatory impairments during sinusoidal cycle exercise even in young, physically active SM with no cardiovascular and respiratory disease.