| Abstrakt: |
Background: Smoking has a thermogenic effect and is associated with low physical performance. Nevertheless, a direct, quantitative effect of acute smoking on exercise heat tolerance has not been reported. Methods: Sixteen healthy young male volunteers, eight cigarette smokers, and eight non-smokers participated in the study. All subjects performed a maximal oxygen consumption test (VO2max) and a standardized heat tolerance test (HTT) after at least 12 h without smoking under the following conditions: no nicotine exposure, 10 min after nicotine exposure (2 mg nicotine lozenge), and 10 min after smoking two cigarettes (0.8 mg nicotine in each cigarette, smokers only). Results: There was no significant effect of nicotine exposure on physiological performance and heat tolerance in the non-smokers group. In the smokers group, cigarette smoking, but not nicotine ingestion, resulted with higher heart rate (by 9 ± 9 bpm) at the end of the HTT (p < 0.05). Moreover, both smoking and nicotine ingestion increased smokers’ rectal temperature at the end of the HTT (by 0.24 ± 0.16 °C and 0.21 ± 0.26 °C, respectively, p < 0.05) and were associated with higher sweat rate during the HTT (by 0.08 ± 0.07 g/h and 0.06 ± 0.08 g/h, respectively, p < 0.05). Heart rate variability (HRV) analysis also revealed a higher LF/HF (low frequency/high frequency) ratio after exposure to nicotine and smoking in the smokers group compared with no exposure (2.13 ± 2.57 and 2.48 ± 2.76, respectively, p < 0.05), indicating a higher sympathetic tone. Conclusions: According to this preliminary study, cigarette smoking and nicotine ingestion increase the physiological strain during a HTT in smokers. Acute smoking may, therefore, increase heat intolerance and the risk to heat injuries. [ABSTRACT FROM AUTHOR] |
