Abstract
Measures characterizing the complexity of heart rate (HR) dynamics have been informative in predicting age- and disease-related decline in cardiovascular health, but few studies have evaluated whether mind-body exercise can impact HR complexity. This study evaluated the effects of long-term Tai Chi (TC) practice on the complexity of HR dynamics using an observational comparison of TC experts and age- and gender-matched TC-naïve individuals. Shorter-term effects of TC were assessed by randomly assigning TC-naïve participants to either TC group to receive six months of TC training or to a waitlist control group. 23 TC experts (age = 63.3 ± 8.0 y; 24.6 ± 12.0 y TC experience) and 52 TC-naïve (age = 64.3 ± 7.7 y) were enrolled. In cross-sectional analyses, TC experts had a higher overall complexity index (CI, p = 0.004) and higher entropy at multiple individual time scales (p < 0.05); these findings persisted in models accounting for age, gender, body mass index (BMI), and physical activity levels. Longitudinal changes in complexity index did not differ significantly following random assignment to six months of TC vs. a waitlist control; however, within the TC group, complexity at select time scales showed statistically non-significant trends toward increases. Our study supports that longer-term TC mind-body training may be associated with increased complexity of HR dynamics.
Highlights
Measures characterizing the complexity of heart rate (HR) dynamics have been informative in predicting age- and disease-related decline in cardiovascular health, but few studies have evaluated whether mind-body exercise can impact HR complexity
This study evaluated the effects of longterm Tai Chi (TC) practice on the complexity of HR dynamics using an observational comparison of TC experts and age- and gender-matched TC-naïve individuals
Meta-analyses and systematic reviews support that Tai Chi may benefit multiple risk factors and clinically relevant outcomes related to cardiovascular health including: lowering systolic and diastolic blood pressure[24]; lowering levels of triglycerides, low-density lipoprotein (LDL), and serum B-type natriuretic peptide (BNP)[25,26]; and improving exercise capacity[27,28,29,30], disease-related quality of life[31], mood[32], sleep quality[33], and exercise self-efficacy[27,34]
Summary
Participant characteristics and flow through the trial. and Tai Chi naïve individuals (N = 60) took place between March 2011 and March 2013, and follow-up assessments were completed in September 2013. Tai Chi experts exhibited an overall higher MSEmod complexity index over 20 scales (CI1–20) compared to Tai Chi naïve controls (CI1–20 of 1.69 ± 0.13 vs 1.57 ± 0.18, p = 0.004) (Fig. 2) This group difference remained statistically significant in linear models adjusting for age, BMI, and physical activity (P = 0.002). Conventional time domain parameters did not show any difference between Tai Chi experts and naïve controls, even after adjusting for age, BMI, level of activity and breathing (Table 2). There was a trend towards a greater increase in the overall MSEmod complexity index (CI1–20) in healthy TC naïve adults randomly assigned to 6 months of Tai Chi (1.52 ± 0.2 to 1.58 ± 0.13) versus usual care group (1.63 ± 0.13 to 1.65 ± 0.14). In contrast to MSEmod, conventional time domain parameters of HRV did not show any trends when longitudinal comparisons were made between those randomly assigned to Tai Chi versus usual care (Table 3)
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