Introduction: There is an established link between smoking, abnormal heart rate (HR) values, and impaired
cardiovascular health in middle-aged or older populations. The purpose of this study was to examine the effects
of smoking on resting HR and on HR responses during and after exercise in young adults.
Methods: A sample of 298 young adults (159 men), aged 20-29 years old, were selected from a large population
of health-science students based on health status, body mass index, physical activity, and smoking
habit. All subjects underwent a maximal Bruce treadmill test and their HR was recorded during, at peak, and
after termination of exercise.
Results: Smokers had significantly higher resting HR values than non-smokers. Both female and male
smokers showed a significantly slower HR increase during exercise. Female smokers failed to reach their
age-predicted maximum HR by 6.0 bpm and males by 3.6 bpm. The actual maximum HR achieved (HRmax)
was significantly lower for both female smokers (191.0 bpm vs.198.0 bpm) and male smokers (193.2 bpm
vs.199.3 bpm), compared to non-smokers. Heart rate reserve was also significantly lower in female (114.6
bpm vs. 128.1 bpm) and male smokers (120.4 bpm vs. 133.0 bpm). During recovery, the HR decline was
significantly attenuated, but only in female smokers. Females had a higher resting HR and showed a higher
HR response during sub-maximal exercise compared to males.
Conclusions: Smoking was found to affect young smokers’ HR, increasing HR at rest, slowing HR increase
during exercise and impairing their ability to reach the age-predicted HRmax. In addition, smoking was associated
with an attenuated HR decline during recovery, but only in females.