Improved aerobic capacity in a randomized controlled trial of noncombustible nicotine and tobacco products.

Smoking negatively impacts aerobic capacity, primarily by reducing V̇O2max, the gold standard measure of cardiorespiratory fitness. While smoking cessation is known to improve vascular function, exercise performance, and oxygen uptake, its specific impact on V̇O2max remains underexplored. Specifically, no research has yet evaluated V̇O2max changes following a switch to electronic cigarettes (ECs) or heated tobacco products (HTPs). This is a secondary analysis of the CEASEFIRE trial, a 12-weeks randomized controlled switching trial comparing the impact of ECs or HTPs on changes in smoking behaviour. The trial offers a unique opportunity to prospectively examine the relationship between smoking behavior and aerobic capacity, and to examine-for the first time-the specific impact of exclusive EC or HTP use on V̇O2max. Changes in VO₂max were analized across three smoking phenotypes: continuous smokers, those who reduced smoking, and those who abstained from smoking Additionally, VO2max was also evaluated specifically in participants who completely abstained from smoking tobacco cigarettes, evaluating outcomes in exclusive EC and HTP users. Quitters showed the greatest improvement in VO2max at both week 4 (2.4 ± 1.7 mL kg min) and week 12 (2.7 ± 1.9 mL kg min). Reducers also exhibited significant VO2max increases (1.3 ± 1.9 mL kg min at week 4: 1.9 ± 1.8 mL kg min at week 12), while Failures (i.e. those who continued smoking) showed no change. Exclusive use of EC and HTP resulted in statistically significant and clinically relevant improvements in V̇O2max. Compared to baseline, V̇Omax significantly increased at week 4 (EC: 38.4 ± 5.9 to 41.0 ± 6.1 mL kg min; HTP: 39.2 ± 6.7 to 41.4 ± 6.4 mL kg min, both p  < 0.0001) and week 12 (EC: 38.4 ± 5.9 to 41.4 ± 6.3; HTP: 39.2 ± 6.7 to 41.6 ± 6.5 mL kg min, both p < 0.0001). No significant differences between EC and HTP were observed at either time point. Rapid improvements in V̇O2max can happen when healthy smokers switch to exclusive use of ECs or HTPs. These findings reinforce the potential cardiorespiratory benefits of smoking cessation and harm reduction strategies.