A study challenges the idea that “more exercise is always better,” revealing how elite cyclists may burn through their daily heartbeats faster. This raises new questions about the fine line between fitness and fatigue.
Study: Balancing Exercise Benefits Against Heartbeat Consumption in Elite Cyclists. Image Credit: Duncan Andison / Shutterstock.com
In a recent JACC: Advances study, researchers examined the relationship between exertional increases and lower resting heart rates in athletes. The concept of ‘heartbeat consumption’ is introduced as a conceptual and hypothesis-generating model that provides insights into the possible adverse effects of intense exercise and training load.
Exercise and resting heart rate
During physical exercise, the body is subjected to increased metabolic demand, to which the cardiovascular system responds to support increased oxygen and nutrient delivery to active muscles. This acute rise in heart rate can be used to evaluate performance intensity, as well as long-term cardiovascular modelling that may occur as a result habitual exercise.
Despite the health benefits of regular physical exercise, the long-term implications of sustained high-intensity training remain unclear. Existing evidence suggests that the total number of heartbeats that an organism produced throughout their lifetime is relatively fixed, with higher than average heart rates inversely correlated with life expectancy.
About the study
The researchers of the current study performed an exploratory analysis to examine the association between the average 24-hour heart rate and exercise training. Using 24-hour Holter monitoring, they examined the average heart rate in a sample of 38 healthy controls and 109 athletes from the Australian cohort of the Pro@Heart study.
Study participants wore the Holter monitor while performing their normal activities and exercise, which recorded heart rate, rhythm, and an accelerometer-derived estimate of activity time.
Sex ratios were similar, as 69.6% and 68.4% of athletes and controls were male. The median age of the athletes was slightly lower at 19 years, as compared to controls with a median age of 21 years. In both groups, the accuracy of the recordings was excellent.
Study findings
The average heart rate was higher in the control group at 76 beats/minute than in the athletes at 68 beats/minute, regardless of sex. This difference in mean heart rates was attributed to the lower resting heart rates among athletes, as only 7.6% of athletes had heart rates exceeding 100 bpm compared to 9.4% of controls. On average, this corresponded to approximately 11,520 or about 10.6% fewer heartbeats per day in athletes, illustrating the potential long-term benefit of a lower resting heart rate.
More intense or prolonged exercise may potentially offset the resting bradycardia in athletes and have a different effect on the total daily heart rate exposure. To assess this phenomenon, exercise data of 22 male and 35 female professional cyclists were examined.
To estimate the number of heartbeats that were exhausted during the race, the total minutes of exercise were multiplied by the average heart rate during each stage. An average of 35,177 heartbeats was reported during each stage, with no differences observed between sexes. However, the researchers note that women's stages, although shorter in duration, were completed at higher average heart rates (about 148 vs. 127 bpm in females and males, respectively), resulting in similar total heartbeat counts between sexes.
These exertional data were combined with average 24-hour heart rates from the Pro@Heart study to estimate cumulative daily heartbeats using the time outside of racing. Overall, resting bradycardia was significantly lower than the heart rate burden during a professional stage race, which suggests prolonged and extreme exercise can increase the average heart rate.
Conclusions
The researchers of the current study introduce the concept of “heartbeat consumption” as an easy-to-interpret yet preliminary metric to monitor how training load and intense exercise may have adverse effects on cardiovascular health. Using this information, healthcare professionals can refer to an optimal exercise dose and identify warning signs of overtraining. Considering the ubiquitous use of smartwatches, gathering data on heart rates should be relatively easy.
Importantly, the study findings on cyclists are inconclusive and are meant to be hypothesis-generating. However, these observations suggest that high-intensity exercise may compromise metabolic energetics. The authors also propose that a higher vagal tine in trained athletes may act as a protective mechanism, linking lower resting heart rate to more efficient metabolic function.
The heartbeat consumption model offers novel insights into the U-shaped curve of exercise benefits. Nevertheless, these findings must be further validated using larger sample sizes while also considering potential confounding factors like age, fitness level, and potential sex-specific differences in exercise-induced heart rate changes.
Journal reference:
- Van Puyvelde, T., Janssens, K., Spencer, L., et al. (2025). Balancing Exercise Benefits Against Heartbeat Consumption in Elite Cyclists. The Journal of the American College of Cardiology Advances 4(10). doi:10.1016/j.jacadv.2025.102140
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