(1) Background: Aquatic exercise training is a relatively understudied exercise modality in patients with CAD; with the present study, we sought to compare the impact of short-term 14-day water- and land-based exercise training on heart rate variability (HRV).
(2) Methods: We randomized 90 patients after a recent CAD event (myocardial infarction and/or revascularization within 2 months prior to inclusion) to either (i) water-based or (ii) land-based exercise training (14 days, two 30 min sessions daily), or (iii) controls. Before and after the intervention period, all participants underwent 20 min 12-channel high-resolution ECG recordings with off-line HRV analysis, including onventional
linear time- and frequency-domain analysis (using the Welch method for fast-Fourier transformation), and preselected non-linear analysis (Poincaré plot-derived parameters, sample entropy, and the short-term scaling exponent α1 obtained by detrended fluctuation analysis).
(3) Results: Eighty-nine patients completed the study (mean age 60 ± 8 years; 20 % women). We did not detect significant differences in baseline- or age-adjusted end-of-study HRV parameters, but aquatic exercise training was associated with a significant increase in the linear LF/HF parameter (from 2.6 [1.2–4.0] to 3.0 [2.1–5.5], p = 0.046) and the non-linear α1 parameter (from 1.2 [1.1–1.4] to 1.3 [1.2–1.5], p = 0.043).
(4) Conclusions: Our results have shown that a short-term 14-day aquatic exercise training program improves selected HRV parameters, suggesting this mode of exercise is safe and may be beneficial in patients with CAD.
This is the largest study comparing water- and land-based exercise training (vs. unsupervised exercise routine controls) in patients after a recent CAD event, and the first to
address HRV. Our results have shown that a short-term 14-day aquatic exercise training program is associated with specific HRV changes, which suggests that this mode of exercise is safe and may be beneficial in patients with CAD.
Keywords: exercise training; aquatic (water-based) exercise; heart rate variability; coronary artery disease