Category: The Physiological Effect of Temperature, Physical Exercise, and Caffeine on the Heart’s Rhythmic Cycle of Contraction in the Human Cardiovascular System

The aim of this study was to assess the effects of hot and cold temperature exposure, physical exercise, and caffeine ingestion on various cardiovascular system response parameters in humans. For this purpose, the heart’s rhythmic cycle of contraction and volume pulse were monitored and measured electrically via an electrocardiogram. To measure the effects of temperature, subjects were exposed to moderately warm water (50ºC) and ice water (0ºC) on the surface of their forearm using a plastic bag. The effects of hand and leg exercise on the cardiovascular system were measured by squeezing a hand dynamometer and by walking stairs, respectively. The effects of caffeine were measured after subjects had consumed 250 ml of unsweetened coffee, an equivalence of 100 mg’s of caffeine. It was found that heat stress, physical exercise, and caffeine ingestion induced a stimulatory effect on cardiovascular response, while cold stress generated an opposite response. It is suggested that the cardiovascular response pattern reported during physical exercise and heat stress is partially due to increased core temperature, which functions as a major factor driving active sympathetic vasodilator activity. In this manner, the opposite is true during cold stress, which stimulates vasoconstriction. Finally, it is possible that caffeine blocks the biochemical process leading to vasoconstriction. These findings indicate that once a stressor is exerted on the subject, cardiovascular response is altered in a manner where blood flow is ultimately modified.