THE EFFECTS OF SMOKING ON EXERCISE HEAT TOLERANCEDruyan AmitAtias DanitMuginshtein JeniKetko ItayFleishman ChenCohen-Sivan YoavYanovich RanHelled Yuval

• 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

• 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.

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

Cigarettes – active ingredients

Tar•Increases Endothelin-1 (a vasoconstrictant)•Decreases NO release (a vasodilator)

>> Negative effect on vasodilation

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.

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

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.

Cigarettes – Effect on physical performance• Lower tolerance for prolonged aerobic physical

activity >> 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)

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.

Exertional Heat Stroke risk facrots

Study goals• To examine the effect of acute smoking and nicotine

ingestion on physical performance and exercise heat tolerance.

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).

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

in both groups.

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=0.025P=0.019

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.

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=0.049P=0.016

Tc during the HTT

P=0.003

P=0.036

Non-smokers

Smokers

HR during the HTT

P=0.043

Non-smokers

Smokers

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.

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