Heart rate response at the onset of exercise in an apparently healthy cohort

Abstract

The exercise test is a powerful non-invasive tool for risk stratifying patients with or suspected of having cardiovascular disease (CVD). Heart rate (HR) response during and following exercise has been extensively studied. However, the clinical utility of HR response at the onset of exercise is less understood. Furthermore, conflicting reports exist regarding whether a faster vs. slower HR acceleration represents a CVD risk marker. The primary study purpose was to describe HR acceleration early in exercise in apparently healthy individuals. Retrospective analyses were performed in a sample (N=947) representing a range of age and fitness (11-78years; VO2peak 17-49mLkg(-1)min(-1)). HR response was defined over the initial 7min of the protocol. Associations between HR acceleration and CVD risk factors were also assessed. Mean increases in HR were 18±9 and 23±11 beats at minute one, for men and women, respectively (p<0.05). After adjusting for gender and pre-exercise HR, only modest associations were observed between the change in HR at minute one and body mass index, resting blood pressure, cigarette smoking, physical activity, HR reserve, and cardiorespiratory fitness. There was wide variability in HR acceleration at the onset of exercise in this apparently healthy cohort. A lower increase in HR during the first minute of exercise was associated with a better CVD risk profile, including higher cardiorespiratory fitness, in apparently healthy individuals. These data suggest a greater parasympathetic influence at the onset of exercise may be protective in an asymptomatic population.