Physical activity is effective in preventing and treating cardiovascular disease (CVD). However, high-level physical activity may pose potential health risks. An elevated resting heart rate is indicative of poor cardiovascular function, yet the safety of physical activity in individuals with high resting heart rates remains unclear. This study aimed to investigate the joint association of resting heart rate and physical activity with CVD risk to provide evidence for individualized exercise guidance.

This study included 5 672 middle-aged and older adults from the China Health and Retirement Longitudinal Study database. Generalized additive models were employed to explore the independent and joint associations of resting heart rate and physical activity with CVD risk. Multiple logistic regression was further used to examine their correlations, while three-dimensional surface plots and two-dimensional slice plots at fixed resting heart rate levels were generated to visualize the nonlinear associations.

A significant nonlinear interaction was observed between resting heart rate, physical activity, and CVD risk (P for interaction <0.001). Compared with the reference group (normal resting heart rate and moderate physical activity), individuals with a resting heart rate >100 beats per minute and low physical activity had the highest risk of CVD (OR=6.223). Among those with high resting heart rate, moderate physical activity was associated with a possible increase in risk (OR=2.059), whereas high physical activity showed no statistically significant association with CVD risk (OR=0.956).

In individuals with a high resting heart rate, high-level physical activity is not associated with an increased risk of CVD. Increasing physical activity represents a universally applicable, low-cost, and effective health promotion strategy.