The influence of aerobic fitness on electrocardiographic and heart rate variability parameters in young and older adults

  • Tristan W. Dorey
    School of Health and Human Performance, Division of Kinesiology, Dalhousie University, Halifax B3H 4R2, Nova Scotia, Canada

    Libin Cardiovascular Institute of Alberta, Department of Cardiac Sciences, Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary T2N 4N1, Alberta, Canada
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  • Myles W. O'Brien
    School of Health and Human Performance, Division of Kinesiology, Dalhousie University, Halifax B3H 4R2, Nova Scotia, Canada
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  • Derek S. Kimmerly
    Corresponding author at: School of Health and Human Performance, Division of Kinesiology, Dalhousie University, 6230 South Street, Halifax B3H 4R2, Nova Scotia, Canada.
    School of Health and Human Performance, Division of Kinesiology, Dalhousie University, Halifax B3H 4R2, Nova Scotia, Canada
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Published:January 28, 2019DOI:


      • Ageing produces longer periods of atrial depolarization.
      • Greater aerobic fitness is linked with longer atrial electrical conduction times.
      • Older, fit adults have longer atrial durations vs. young and less fit older adults.
      • This latter finding may be due to enhanced vagal tone and/or cardiac remodeling.


      Long-term endurance training is associated with an increased risk of atrial arrhythmia in older adults (OA). We tested the hypothesis that Aerobically-Fit OA would have prolonged indices related to atrial arrhythmias (e.g. PR-intervals and P durations) compared to younger adults (YA) and Aerobically-Unfit OA. 10–minute stable supine electrocardiogram (ECG) recordings were collected at 1000 Hz in 15 YA (4F, 22 ± 2 years, 50.7 ± 8.5 ml/kg/min), 11 Aerobically-Unfit OA (6♀, 63 ± 7 years, 25.2 ± 2.3 ml/kg/min) and 10 Aerobically-Fit OA (4F, 64 ± 3 years, 45.5 ± 7.0 ml/kg/min) to assess ECG morphology and spectral indices of heart rate variability. In the pooled sample, age was a predictor of PR-interval (r = 0.75) and P wave duration (r = 0.80) (both, p < 0.01). Regardless of age, aerobic fitness was positively associated with PR interval duration (r = 0.81; p < 0.01). Aerobically-Fit OA had prolonged PR-intervals (187 ± 17 vs 161 ± 14 vs. 168 ± 20 ms) and P-wave durations (123 ± 9 vs. 97 ± 9 vs. 96 ± 9 ms) compared to YA and Aerobically-Unfit OA, respectively (all, p < 0.05). In addition, Aerobically-Fit OA had greater normalized high-frequency (HF) power compared to Aerobically-Unfit OA (40.7 ± 4.5nu vs. 30.1 ± 14.2 ± nu; p = 0.03) suggestive of enhance parasympathetic tone. These data highlight that the combination of age-related electrical remodeling and enhanced vagal tone in OA with higher aerobic fitness may contribute to prolongation of atrial-related ECG indices. This is further supported by the correlation between HF power and PR-interval duration (r = 0.45; p = 0.02). These findings may help identify older individuals at risk for atrial arrhythmias who are otherwise free of cardiovascular disease.


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