Cover Photo: Allie Egolf. June, 2019.

Resting Heart Rate: What Your Heartbeat Says About Your Fitness

A strong heart is a hallmark of good health. One of the simplest ways to gauge your heart’s efficiency is by measuring your resting heart rate (RHR)—the number of beats per minute when you’re at complete rest. The lower your RHR, the more efficiently your heart pumps blood. While traditional endurance training is often credited with producing the lowest RHR, high-intensity interval training (HIIT) has also been shown to deliver substantial cardiovascular benefits. But which approach is best?

Understanding Resting Heart Rate

Resting heart rate is more than just a number—it’s a key indicator of cardiovascular health. A lower RHR generally means your heart doesn’t have to work as hard to circulate blood, reducing stress on the heart and lowering the risk of cardiovascular disease (Liang et al., 2024).

• Typical Ranges: Most adults have an RHR between 60 and 100 beats per minute (bpm). Well-trained endurance athletes often see values as low as 40-50 bpm (Huang et al., 2015).
• Why It Matters: A lower RHR is associated with greater heart efficiency, better aerobic fitness, and longevity. Conversely, a higher RHR is linked to an increased risk of heart disease and all-cause mortality (Grässler et al., 2021).

Training Methods to Lower Resting Heart Rate

Steady-State Endurance Training: The Traditional Approach

Endurance training—such as long-distance running, cycling, and rowing—has long been the gold standard for improving cardiovascular efficiency. Studies show that prolonged aerobic exercise increases stroke volume, which is the amount of blood pumped per beat. This allows the heart to work less while delivering the same amount of oxygen to muscles (Cornelissen & Fagard, 2005).

Endurance training strengthens the heart muscle, enlarges the left ventricle, and enhances vagal tone, which helps regulate heart function. This process leads to a consistently lower RHR. Research published in Frontiers in Physiology indicates that endurance training leads to significant reductions in RHR through increased stroke volume and autonomic regulation (Cornelissen & Fagard, 2005).

Sprint Training and HIIT: A New Contender

High-intensity interval training (HIIT), which alternates short bursts of near-maximal effort with periods of rest, has gained popularity for its time-efficient benefits. While HIIT is best known for improving anaerobic power and metabolic efficiency, it also influences RHR.

Studies suggest that HIIT can rival steady-state endurance training in its ability to lower RHR. The rapid heart rate fluctuations during intervals may improve autonomic nervous system balance, reducing resting sympathetic activity and enhancing parasympathetic tone (Oliveira et al., 2022). A study in the International Journal of Environmental Research and Public Health found that HIIT can significantly reduce RHR while also improving heart rate variability, a key marker of autonomic nervous system function (Oliveira et al., 2022).

Photo: MCRD San Diego. 2024. LCpl Francisco Angel, USMC

Individual Variability in Response

Despite scientific consensus that endurance training lowers RHR effectively, many individuals, including myself, have found that sprint training produces greater reductions in RHR. This discrepancy may be due to several factors:

• Genetic Variability: Some people naturally respond better to high-intensity training, experiencing greater autonomic adaptations (Liang et al., 2024).
• Training History: Those with a background in strength training may find HIIT more effective due to its neuromuscular demand and metabolic effects (González-Gálvez et al., 2024).
• Intensity vs. Duration: HIIT can be a time-efficient way to reap cardiovascular benefits without the high mileage required for endurance adaptations (Stursová et al., 2023).

The Operator’s Edge: How Training Lowers Your Heart Rate and Boosts Performance

Understanding how different training styles affect heart function comes down to cellular adaptations:

1. Cardiac Remodeling: Both endurance and HIIT training increase left ventricular mass, allowing for greater stroke volume and lower RHR (Cornelissen & Fagard, 2005).
2. Autonomic Nervous System Regulation: Training enhances vagal (parasympathetic) activity while reducing sympathetic dominance, leading to a calmer resting state (Grässler et al., 2021).
3. Increased Capillary Density: More blood vessels mean improved oxygen delivery, which in turn reduces the heart’s workload (Stursová et al., 2023).

Key Takeaways

• Both endurance and HIIT training can effectively lower RHR, but endurance training has the strongest track record for achieving the lowest values.
• Individual responses vary, and some people may see greater benefits from HIIT based on genetics and training history.
• Training adaptations are driven by increased stroke volume, autonomic nervous system balance, and improved vascular efficiency.
• For those with time constraints, HIIT provides an effective and efficient alternative to steady-state cardio.

Conclusion

Lowering your resting heart rate is a sign of improved cardiovascular efficiency and longevity. While steady-state endurance training has long been the preferred method, HIIT presents a compelling alternative with comparable benefits. The best approach is the one that fits your lifestyle and keeps you consistent. If your goal is to optimize heart health, experiment with both methods and track your progress. Your heart will thank you for it.

References

Cornelissen, V. A., & Fagard, R. H. (2005). Effects of endurance training on blood pressure, blood pressure-regulating mechanisms, and cardiovascular risk factors. Hypertension, 46(4), 667-675.

González-Gálvez, N., López-Gil, J. F., Espeso-Garcia, A., Abenza-Cano, L., Mateo-Orcajada, A., & Vaquero-Cristóbal, R. (2024). Effectiveness of high-intensity and sprint interval training on metabolic biomarkers, body composition, and physical fitness in adolescents. Frontiers in Public Health, 12, 1425191.

Grässler, B., Thielmann, B., Böckelmann, I., & Hökelmann, A. (2021). Effects of different training interventions on heart rate variability and cardiovascular health and risk factors in young and middle-aged adults: A systematic review. Frontiers in Physiology, 12, 657274.

Huang, G., et al. (2015). Effects of exercise on the resting heart rate: A systematic review and meta-analysis of interventional studies. Journal of Clinical Medicine, 4(11), 1908–1927.

Liang, W., et al. (2024). Effects of high-intensity interval training on the parameters related to physical fitness and health of older adults: A systematic review and meta-analysis. Sports Medicine – Open, 10, 98.

Oliveira, J., et al. (2022). Effects of high-intensity interval training versus sprint interval training on cardiac autonomic modulation in healthy women. International Journal of Environmental Research and Public Health, 19, 12863.

Stursová, P., et al. (2023). Sports activities and cardiovascular system change. Physiological Research, 72(Suppl. 5), S429-S444.