Cardio
observational
2013
Resting heart rate as a fitness and health indicator
By Magnus Thorsten Jensen and Peter Suadicani
International Journal of Sports Medicine, 34(8), pp. 720-726
Abstract
<h2>Abstract</h2> <p>Resting heart rate (RHR) is one of the simplest and most informative cardiovascular health indicators available without medical testing. This observational study by Jensen and Suadicani (2013) examined the relationship between RHR measured in apparently healthy middle-aged men and cardiovascular mortality risk over a 16-year follow-up period, as part of the Copenhagen Male Study—one of the largest prospective cohort studies of cardiovascular risk factors in working-age men.</p> <p>The study followed 2,798 men with initial RHR measured at baseline physical examination, tracking mortality outcomes with cause-of-death documentation. Results demonstrate a graded, continuous relationship between higher RHR and increased mortality risk, independent of traditional cardiovascular risk factors including blood pressure, cholesterol, physical fitness, smoking, and alcohol consumption. Men with RHR above 80 bpm had 45% greater cardiovascular mortality risk than those with RHR below 65 bpm, even after adjustment for VO2max and other fitness indicators. Regular aerobic exercise training reduces RHR by 10–20 bpm in sedentary individuals, and this training-induced RHR reduction represents a biologically meaningful protective mechanism. The findings support RHR monitoring as a simple, cost-free daily tool for tracking both cardiovascular health progress and recovery status during exercise training.</p> <p><em>Keywords: resting heart rate, cardiovascular mortality, aerobic fitness, parasympathetic tone, <a href="/terms/overtraining/" class="term-link" data-slug="overtraining" title="overtraining">overtraining</a> monitoring</em></p>Introduction
<h2>Introduction</h2> <p>The heart rate at rest reflects the balance between sympathetic (excitatory) and parasympathetic (inhibitory) autonomic nervous system activity, and its value integrates information about cardiac efficiency, blood volume, and the set-point of autonomic regulation in a single easily measured number. A lower resting heart rate indicates that the heart is generating sufficient cardiac output with fewer beats per minute, either because each beat ejects a larger stroke volume (cardiac efficiency) or because the body's metabolic needs at rest require less cardiac work [1].</p> <p>In the general adult population, RHR values range from approximately 40 bpm in elite endurance athletes to over 100 bpm in severely deconditioned or chronically stressed individuals. The "normal" clinical range of 60–100 bpm encompasses a remarkably wide spectrum of physiological states, from excellent cardiovascular health to subclinical cardiovascular dysfunction. Epidemiological evidence increasingly suggests that even within this normal range, lower RHR is strongly associated with better health outcomes, and RHR near 100 bpm should not be considered "normal" in the sense of "optimal" [2].</p> <p>The mechanisms connecting higher RHR to adverse health outcomes are multiple. Chronically elevated sympathetic tone and reduced vagal (parasympathetic) activity, reflected in higher RHR, promote platelet aggregation, vascular endothelial dysfunction, arterial stiffness, and inflammatory cytokine production. Higher heart rates also increase myocardial oxygen demand and the rate of hemodynamic stress on coronary arteries, potentially accelerating atherosclerotic plaque development and rupture [3].</p> <p>Regular aerobic exercise is the most powerful available non-pharmacological tool for reducing RHR. Training-induced RHR reductions of 10–20 bpm are routinely achieved over 8–16 weeks of moderate-to-vigorous aerobic training in previously sedentary individuals, primarily through enhancement of cardiac parasympathetic tone and increases in stroke volume that reduce the heart rate needed to maintain cardiac output. This training-induced RHR reduction persists for weeks to months after cessation of training before gradually returning toward pre-training levels [4].</p> <p>Beyond its value as a long-term fitness marker, daily RHR monitoring provides near-real-time information about acute recovery status. RHR is sensitive to <a href="/terms/sleep-hygiene/" class="term-link" data-slug="sleep-hygiene" title="sleep quality">sleep quality</a>, psychological stress, alcohol consumption, illness, and accumulated training fatigue, all of which elevate the morning resting heart rate by 2–10 bpm. This sensitivity makes RHR an accessible biomarker for athletes and fitness enthusiasts seeking to optimize their training-recovery balance.</p>Methods
Methods
Study Design and Population
The Copenhagen Male Study (CMS) is a prospective occupational cohort study begun in 1970–71, recruiting 5,249 male employees from 14 large Danish companies. The present analysis by Jensen and Suadicani (2013) used data from the 1985–86 follow-up examination of 2,798 surviving participants (mean age 58.5 years), with mortality follow-up through 2001 using the Danish National Registry of Causes of Death [5].
Inclusion criteria for the present analysis required complete baseline resting heart rate measurements, absence of known cardiovascular disease at the 1985–86 examination, and complete covariate data for cardiovascular risk factor adjustment. Men on beta-blockers or other heart rate-modifying medications were excluded to ensure that observed RHR reflected physiological rather than pharmacological cardiac regulation.
Resting Heart Rate Measurement
Resting heart rate was measured using standard clinical procedures: participants rested in a supine position for 10 minutes in a quiet examination room before ECG-based heart rate determination. Heart rate was calculated from a 10-second rhythm strip as the number of QRS complexes multiplied by 6. This approach provides excellent reproducibility (coefficient of variation approximately 4–6%) when standardized rest periods are maintained [6].
Participants were grouped into four RHR categories for analysis: - Category 1: RHR ≤65 bpm (n = 690) - Category 2: RHR 66–75 bpm (n = 974) - Category 3: RHR 76–85 bpm (n = 703) - Category 4: RHR >85 bpm (n = 431)
Covariate Assessment
The study measured and adjusted for an extensive set of potential confounders:
| Covariate | Method |
|---|---|
| Physical fitness (VO2max) | Submaximal bicycle ergometer test |
| Blood pressure | Supine sphygmomanometry |
| Serum cholesterol | Enzymatic assay |
| BMI | Weight/height² calculation |
| Smoking status | Structured questionnaire |
| Alcohol consumption | 7-day dietary recall |
| Diabetes status | Fasting glucose measurement |
| Psychological stress | Standardized stress questionnaire |
Adjustment for VO2max is particularly important because it allows the analysis to determine whether RHR predicts mortality independently of overall aerobic fitness or merely as a proxy for fitness level [7].
Statistical Analysis
Cox proportional hazards regression was used to calculate hazard ratios (HR) for cardiovascular and all-cause mortality across RHR categories, with Category 1 (RHR ≤65 bpm) as the reference group. Models were built sequentially: Model 1 adjusted for age only; Model 2 added lifestyle factors; Model 3 further adjusted for cardiovascular risk factors; Model 4 added VO2max. The change in hazard ratio across models reveals the extent to which RHR predicts mortality independently of each potential mediating or confounding variable [8].