Fractal scaling properties of heart rate dynamics following resistance exercise training

Kevin S. Heffernan, Jacob J. Sosnoff, Christopher A. Fahs, Kevin K. Shinsako, Sae Young Jae, Bo Fernhall

Research output: Contribution to journalArticlepeer-review


With aging and disease, there is a breakdown of the natural fractal-like organization of heart rate (HR). Fractal-like correlation properties of HR can be assessed with detrended fluctuation analysis (DFA). A short-time scaling exponent (αs) value of 1 is associated with healthy HR dynamics, whereas values that deviate away from 1, in either direction, indicate fractal collapse. The purpose of this study was to examine the effect of resistance exercise training (RT) on fractal correlation properties of HR dynamics. Resting ECG was collected at baseline, following a 4-wk time control period and 6 wk of RT (3 days per wk) in 34 men (23 ± 1 years of age). Fractal properties of HR were assessed with DFA. There was no change in α2 following either the time control period or RT (1.01 ± 0.06 to 0.98 ± 0.06 to 0.93 ± 0.04, P > 0.05). Given the potential bidirectional nature of fractal collapse, subjects were retrospectively separated into two groups (higher αs and lower αs) on the basis of the initial αs by using cluster analysis. An interaction was detected for αs following RT (P < 0.05). There was no change in αs in either group following the time control, but αs increased following RT in the lower αs group (n = 18; 0.73 ± 0.04 to 0.69 ± 0.04 to 0.88 ± 0.04) and αs decreased following RT in the higher αs group (n = 16; 1.20 ± 0.04 to 1.24 ± 0.04 to 0.98 ± 0.04). In conclusion, RT improves fractal properties of HR dynamics.

Original languageEnglish (US)
Pages (from-to)109-113
Number of pages5
JournalJournal of Applied Physiology
Issue number1
StatePublished - Jul 2008


  • Autonomic nervous system
  • Nonlinear

ASJC Scopus subject areas

  • General Medicine


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