The Effects of Smoking on Exercise Heat Tolerance

1. The Effects of Smoking on Exercise Heat Tolerance DruyanAmit AtiasDanit MuginshteinJeni KetkoItay Fleishman Chen Cohen-Sivan Yoav Yanovich Ran Helled Yuval

2. Cigarette smoking is the leading preventable cause of mortality. • Nicotine abuse is the most common substance abuse in the world. • Smokers who stop smoking reduce their risk of developing and dying from tobacco-related diseases

3. Smoking amongst soldiers decreases physical fitness • Smoking increases clinic visits and sick leaves among soldiers. • Smokers succeed less during basic training • In the US army smoking was forbidden during basic training in the 1980’s.

6. Cigarettes – active ingredients Carbon Monoxide (CO) • Higher affinity to HB than O2 (X200) >> decreases O2 carrying capacity. • Decreases O2 dissociation in the muscle tissues. >> relative hypoxia in the muscle tissue >> lower Vo2 max

7. Cigarettes – active ingredients Tar • Increases Endothelin-1 (a vasoconstrictant) • Decreases NO release (a vasodilator) >> Negative effect on vasodilation

8. Cigarettes – active ingredients Nicotine • Smoking 1 cigarette delivers 1-2 mg of nicotine to the smoker • Increases blood Cathecholamines (increases sympathetic activity) -> increases: HR, peripheral vasoconstriction, BP. • Increases sympathetic activity and increases RMR.

9. Cigarettes – active ingredients Nicotine • Chronic nicotine ingestion >> beta adrenergic receptors down-regulation>> lower use of fatty acids and higher dependence on glucose (prolonged exercise?) • Increases platelets aggregation>> elevates blood viscosity. • Increases Vasopressin, β-endorphin, ACTH, Cortisol, GH and Prolactin

10. Cigarettes – active ingredients Nicotine • Toxic to Osteoblasts, Fibroblasts, Macrophages and causes endothelial damage. • Increases the sweat rate, m/p by sympathetic acticity. • Causes de-sensitization and up-regulation of nAChRs, thus response to nicotine is different between smokers and non-smokers.

11. Cigarettes – Effect on physical performance • Lower tolerance for prolonged aerobic physicalactivity >> smokers report earlier exhaustion, dyspnea, muscle pain • Young healthy smokers and non-smokers have similar aerobic fitness. • Acute smoking decreases VO2max after smoking a cigarette. • Smoking increases RMR (smoking 4 cigarettes increases RMR by 33% for 3 hours)

12. Cigarettes – Effect on physical performance • Nicotine doubles energy expenditure during physical activity compared with its resting effect. • Smoking increases the sweat rate during and after smoking. • Smoking decreases cutaneous blood flow. • Smokers have decreased micro-vascular vasomotor function compared to non-smokers.

13. Exertional Heat Stroke risk facrots

14. Study goals • To examine the effect of acute smoking and nicotine ingestion on physical performance and exercise heat tolerance.

15. Study design • 16 young healthy male subjects, 8 smokers & 8 non-smokers. • HRV measurement, VO2max test, HTT – after 12 hours of abstinence, after nicotine ingestion (2 mg lozenges), for the smokers after smoking (2 0.8mg nicotine containing cigarettes).

16. Fitness (VO2max) test • No baseline changes between smokers and non-smokers • No significant change after nicotine ingestion or smoking in both groups.

17. Heart Rate Variability (HRV) • Non-smokers did not react to nicotine • In smokers the LF/HF ratio increased after nicotine ingestion and smoking (increased sympathetic tone) P=0.019 P=0.025

18. Heat Intolerance • 2 out of 8 smokers were found heat intolerant during the baseline HTT. • All non-smokers were found heat tolerant during the baseline HTT.

19. Sweat Rate during the HTT • No baseline changes between smokers and non-smokers • Both nicotine ingestion and smoking increased SR in smokers. Nicotine did not increase SR in non-smokers. P=0.016 P=0.049

20. Tc during the HTT Non-smokers P=0.003 Smokers P=0.036

21. HR during the HTT Non-smokers Smokers P=0.043

23. Conclusions • Acute smoking and nicotine ingestion increase the physiological strain during an exercise heat challenge, thus may be considered as risk factors for heat injuries. • The sympathetic activation of nicotine which causes peripheral vasoconstriction probably plays a major role in the increased physiological strain.

24. סא"ל פרופ' יובל חלד רס"ן דר' רן ינוביץ' רס"ן חן פליישמן סרן (מיל') דר' יואב כהן-סיון דר' דנית אטיאס סרן ג'ני מוגינשטיין סרן איתי קטקו סמל ליאור כגן רב"ט אמיר פרגמן