Cardio Adaptations in Male and Female College Athletes

A new study tracking collegiate triathletes over a full competitive season found that while both men and women got faster, their heart rates didn’t change in ways that explain those improvements. Ronnie Wayne Eggleston Jr. and colleagues monitored nine male and ten female athletes from a university club team from preseason to postseason in the 2025-2026 season.

The research directly compared cardiovascular adaptations between sexes, a topic that has received little attention despite heart rate being a cornerstone of exercise prescription and health assessment.

How the Study Measured Heart and Performance Changes

The researchers used a longitudinal design, taking measurements at the start and end of the athletes’ season. Resting heart rate was recorded after five minutes of quiet rest. Maximal heart rate was defined as the highest value achieved during exertion, likely captured during high-intensity workouts or competitions.

Endurance performance times were collected using standardized institutional methods, combining clocked and chip transmitter data. To analyze the results, the team used statistical models that accounted for the athletes’ individual training levels, ensuring comparisons were fair. They also examined correlations between heart rate changes and performance changes for each sex.

This methodology mirrors the real-world training progression of endurance athletes, making the findings directly applicable to coaches and athletes.

Heart Rate Adaptations Show No Sex-Based Difference

The primary finding on heart rate was clear: there was no statistically significant difference between men and women in how their resting or maximal heart rates changed from preseason to postseason. Both groups exhibited similar patterns of adaptation.

This suggests that the fundamental cardiovascular response to a structured season of triathlon training—at least as reflected in these two common metrics—is not inherently sex-specific. While baseline heart rates often differ between sexes due to size and physiology, their adaptive response to training appears more uniform. This aligns with broader principles of cardiovascular remodeling seen in endurance sports.

Performance Improved, But Not Because of Heart Rate

The most significant result was in performance. The main effect for total endurance performance times was statistically significant, meaning both male and female triathletes got faster over the season. However, the interaction effect with sex was not significant. Men and women improved at similar rates relative to their starting points.

Crucially, the statistical analysis found no significant relationship between the changes in heart rate (either resting or maximal) and the improvements in performance time for either sex. The athletes became more efficient and faster, but these gains were not linked to measurable shifts in their heart rate variables.

This points to other factors driving performance gains. Improved economy, better pacing, enhanced muscular endurance, or technical skills in swimming, cycling, and running are likely candidates. It also reinforces that heart rate, while a useful monitoring tool, is not a sole predictor of performance improvement. This complements discussions on performance models like the polarized training model, where intensity distribution, not just heart rate response, is key.

Practical Implications for Athletes and Coaches

For endurance athletes and their coaches, this study offers several practical insights. First, while monitoring resting and maximal heart rate can provide general health and adaptation data, these metrics alone should not be used to predict or explain race performance improvements. A plateau in heart rate adaptation does not necessarily mean a plateau in performance potential.

Second, training programs for male and female athletes can likely apply similar principles regarding cardiovascular load and adaptation expectations, at least at the collegiate level studied. The focus should remain on proven methods for enhancing endurance: consistent volume, appropriate intensity distribution, and sport-specific skill work. Incorporating strength training, as explored in other disciplines, could be one such method to drive performance without altering heart rate metrics.

Finally, athletes should consider a wider array of metrics to gauge progress. Performance times, perceived effort, power output, and even subjective well-being may be more informative than heart rate changes alone. For those interested in finer autonomic control, techniques like breathing biofeedback could offer complementary tools for managing stress and recovery outside of direct heart rate measurement.

Where Future Research Should Focus

Eggleston’s study, as noted in the source, offers valuable insights for future research. The clear next step is to investigate what physiological or biomechanical factors actually explain the performance gains observed. Candidates include changes in stroke volume, cardiac output, lactate thresholds, or movement economy.

Larger sample sizes and longer observation periods would help confirm these findings. Studying different endurance sports and athlete levels—from novice to elite—would also clarify if these patterns hold true across the spectrum. Furthermore, research could explore if other cardiac adaptations, such as those detailed in studies on athlete heart remodeling, show sex-based differences that this study did not capture.

The research by Ronnie Wayne Eggleston Jr. provides a focused look at a common question in endurance training. It confirms that performance can improve independently of classic heart rate metrics and that, in this domain, male and female athletes may adapt in surprisingly similar ways.

Source: Eggleston, Ronnie Wayne, Jr. Cardiovascular adaptations to exercise in male and female endurance athletes: a focus on heart rate and performance outcomes. Available via OpenAlex and PubMed.