Key result
Low intensity isometric exercise resulted in lower sample entropy (p<0.001) and higher SDNN, low, and high frequency power (p<0.001) compared to dynamic exercise.
Why the study?
Does low intensity isometric exercise compared to dynamic exercise alter heart rate variability and cardiovascular control in healthy males?
RCT (n=43)
Randomized order
Does low intensity isometric exercise compared to dynamic exercise alter heart rate variability and cardiovascular control in healthy males?
p-value: p=<0.001
Isometric and dynamic exercises evoke distinct autonomic cardiovascular responses despite identical heart rates, with isometric exercise enhancing the interplay between autonomic branches.
Findings in healthy males should not yet alter exercise prescriptions; extends evidence on distinct autonomic effects of isometric versus dynamic exercise.
Nonlinear parameters of heart rate variability (HRV) have proven their prognostic value in clinical settings, but their physiological background is not very well established. We assessed the effects of low intensity isometric (ISO) and dynamic (DYN) exercise of the lower limbs on heart rate matched intensity on traditional and entropy measures of HRV. Due to changes of afferent feedback under DYN and ISO a distinct autonomic response, mirrored by HRV measures, was hypothesized. Five-minute inter-beat interval measurements of 43 healthy males (26.0 ± 3.1 years) were performed during rest, DYN and ISO in a randomized order. Blood pressures and rate pressure product were higher during ISO vs. DYN (p < 0.001). HRV indicators SDNN as well as low and high frequency power were significantly higher during ISO (p < 0.001 for all measures). Compared to DYN, sample entropy (SampEn) was lower during ISO (p < 0.001). Concluding, contraction mode itself is a significant modulator of the autonomic cardiovascular response to exercise. Compared to DYN, ISO evokes a stronger blood pressure response and an enhanced interplay between both autonomic branches. Non-linear HRV measures indicate a more regular behavior under ISO. Results support the view of the reciprocal antagonism being only one of many modes of autonomic heart rate control. Under different conditions; the identical “end product” heart rate might be achieved by other modes such as sympathovagal co-activation as well.
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Weippert et al. (2014) conducted an RCT in Healthy (n=43). Low intensity isometric (ISO) exercise vs. Dynamic (DYN) exercise and rest was evaluated on Sample entropy (SampEn) and traditional HRV measures (SDNN, low and high frequency power) (p=<0.001). Low intensity isometric exercise resulted in lower sample entropy (p<0.001) and higher SDNN, low, and high frequency power (p<0.001) compared to dynamic exercise.
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