Introduction
Exercise-based cardiac rehabilitation is a cornerstone of secondary prevention in patients after myocardial infarction or coronary procedure, as it reduces cardiovascular morbidity and mortality.
So far, the exercise type usually studied has been land-based exercise, aerobic and resistive by nature. In cardac patients, dynamic–aerobic exercise training in the form of walking or cycling is recommended as a mens of improving cardiovascular health. Water-based physical activities, however, have traditionally been cautioned against because of the purportedly higher risk of adverse cardiovascular events.
Increased interest in the water exerce, on the one hand, and the lack of sufficient information of the efficacy of short-term water-based exercise on the other, have indicated a need for the scientific evaluation of this type of exercise from the aspect of safety and efficiency in coronary patients.
We hypothesized that water-based exercise training is as safe and effective as land-based training in improving: i) physical performance, ii) vascular function, iii) autonomic cardiac function, iv) biological markers of cardiovascular disease, and v) quality of life. Therefore, we conducted a randomized clinical trial comparing the safety and effects of 14-day water- and land-based exercise training to the usual exercise routines (with no supervised training control) in coronary patients.
Methods
Patients after recent myocardial infarction or coronary revascularization were randomly allocated to two intervention groups and control group (30 patients each).The intervention groups performed supervised aerobic endurance and calisthenics exercise training sessions in thermoneutral water or on land, at a moderate intensity (60–80% peak heart rate achieved at symptom limited exercise testing), for 30 minutes twice a day for 2 weeks. The control group, continued with their usual treatment, but did not participate in any controlled physical exercise program, advised instead to perform low- to moderate-intensity physical activities at home during the course of the study.
Before, and after the intervention, the following examinations were made in all study participants: i) estimation of aerobic exercise capacity (peak oxygen uptake, V̇O2 peak, obtained during cardiopulmonary exercise testing), ii) ultrasound assessment of flow-mediated dilation of the brachial artery during reactive hyperemia, iii) analysis of cardiac autonomic function with a 20-minute high-resolution ECG, iv) determination of the serum concentrations of markers of neurohumoral activity (NT-proBNP), inflammation (hsCRP, IL-6, IL-8, IL-10), endothelial activation (ICAM, P-selectin), and hemostasis (fibrinogen, D-dimer), and v) assessment of the health-related quality of life.
Results
Eighty-nine participants (mean age 59.9 8.2 years; 77.5% males, baseline V̇O peak 14.8 3.5 ml kg-1 min-1) completed the study. One patient was excluded from the study due to upper respiratory tract infection. No adverse events were observed in either of the intervention groups during the course of the study.
Exercise capacity, determined as V̇O2 peak, increased significantly in both training groups in comparison to control. When controlling for baseline V̇O2 peak and patients’ age, mean estimate end-of-study V̇O2 peak improved in the land-based exercise group by up to 15.3% (16.7 [95%CI 16.0 – 17.4]; ml kg -1 min-1; p<0.001 for change from baseline) and up to 27.4% (18.6 [95%CI 17.9 – 19.3] ml kg-1 min-1; p<0.001 for change from baseline) in the water-based exercise group, while the increase was not observed in controls (– 0.6%, 14.9 [95%CI 14.2 – 15.6] ml kg-1 min-1; p=0.775 for change from baseline). The land-based exercise group had an, on average, 1.8 (95%CI 0.8 – 2.8) ml kg-1 min-1 and the water-based exercise group 3.7 (95%CI 2.7 – 4.7) ml kg-1 min-1 higher end-of-study V̇O peak in comparison to control.
Flow-mediated dilation improved in both training groups, with greater improvements after water-based exercise: in the land-based exercise group from 5.5% (interquartile range, IQR: 3.1 – 8.6) to 8.8% (IQR: 5.3 – 11.4), p<0.001 and in the water-based exercise group from 7.2% (IQR: 4.0 – 8.7) to 9.2% (IQR: 7.4 – 12.9), p<0.001. There was no significant improvement in the control group (p=0.629). Non-flow-mediated vasodilation improved significantly in both intervention groups, i.e. in land-based exercise, from baseline values of 10.6% (IQR:7.0 – 13.3) to end-of-study values of 11.1% (IQR: 9.0 – 14.3), p<0.001, and in water-based exercise from the baseline 10.5% (IQR: 8.5 – 14.0) to end-of-study 11.4% (IQR: 7.6 – 13.4), p=0.042.
D-dimer values significantly decreased in the water-based exercise group, from 400 μg L-1 (IQR: 270 – 810) to 370 μg L-1 (IQR: 260 – 590), p<0.001, while in the land-based exercise group we recorded lower but insignificant values in relation to basal. Significant reduction in NT-proBNP values was noticed only in patients in the water-based exercise group, from 396 ngL-1 (IQR: 296 – 541) to 308 ngL-1 (IQR: 187 – 394), ( - 22%, p = 0.001), while in the land-based exercise group no significant changes were noted. There were no significant changes in the values of inflammatory (hsCRP, IL6, IL8, IL 10) and endothelial activation (ICAM, selectin) parameters, or in fibrinogen values.
By analyzing the heart rate variability parameters before and after rehabilitation, we observed no significant changes in the selected time-domain parameters in patients undergoing water- or land-based exercise, or in the control group. Regarding the frequency-domain parameters, we observed a statistically significant change in the high frequency and low frequency parameters ratio (HF/LF) in the group of patients who underwent water-based exercise (p = 0.036). Furthermore, a significant change of indicator of vagal modulation - nonlinear parameter 1 (p = 0.043), and a marginally statistically significant change of another nonlinear parameter SE (p = 0.096), were observed in the same group of patients.
Both types of exercise training were associated with improvements in the mental and physical domains of health-related quality of life.
Conclusion
The results of our study indicate that relatively short supervised water-based exercise training is as safe and effective as land-based exercise training in improving exercise capacity and endothelial function (estimated by flow-mediated dilation) in patients with coronary artery disease, thus providing evidence on an additional modality to propose to patients in cardiac rehabilitation, according to their preference. In addition, we confirmed that water-based exercise is efficient in decreasing serum D-dimer and NT-proBNP concentrations as well as certain indicators of vagal modulation. In improving health-dependent quality of life, both types of exercise were equally effective.
Besides contributing to the growing body of evidence on the effectiveness of exercise training in coronary artery disease patients, our findings confirms that water-based exercise may be a safe and effective exercise option both for patients after a recent coronary event referred to short-term cardiac rehabilitation and as a life-long exercise modality.
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