Investigating cardiolocomotor synchronization during running in trained and untrained males

Abstract

Introduction: This study aims at investigating the coupling of the cardiac and locomotor systems during running in trained and untrained males. Methods: Sixteen healthy young males subjects were submitted to an anthropometric evaluation, followed by a treadmill test at 70% to 75% of heart rate reserve. Based on the average velocity, they were divided into two groups of eight, trained group (TG) and untrained group (UT). The electrocardiogram and the electromyogram of the vastus lateralis muscle of the right thigh were digitized at a sampling rate of 1000 Hz, and processed off-line. Each cardiac and electromyographic cycle was detected to further investigate the coupling between cardiac and running rates in time domain, using the cross-correlation, and in the frequency domain, using a phase synchronization measure based on the Hilbert transform. A Shannon entropy index and magnitude squared coherence were also applied to improve analysis. Results: Both groups presented low cross-correlation (0.18 ± 0.07 TG and 0.15 ± 0.08 UG) values between these signals, and only four from 16 subjects presented short epochs of phase synchronization (4.1 ± 8.6% TG and 3.2 ± 7.3% UG) between signals, occurring at a low frequency band and random phase differences. The low to moderate coherence (0.67 ± 0.16 TG and 0.64 ± 0.16 UG) observed at 0.1 Hz appears to be an effect of the simultaneous action of sympathetic system over both cardiac and muscular rhythms. Conclusion: The combined results suggest that the chosen exercise protocol was not able to cause cardiolocomotor synchronization.

The Entrainment Frequency of Cardiolocomotor Synchronization in Long-Distance Race Emerges Spontaneously at the Step Frequency

“…This frequency centered in the stride frequency was a consequence of cardiolocomotor entrainment, but the authors recognized that it is not easy to identify it because that entrainment frequency was overlapping the autonomic nervous system frequencies ( Bailón et al, 2013 ). In the other study ( Materko et al, 2015 ), just one participant presented short epochs of phase synchronization, but this occurred at the frequency compatible with the sympathetic nervous system band of frequency.…”

“…External oscillators may influence the neural drive, and probably it will be the reason to the coherence between two signals from different sources ( Farina et al, 2014 ). We speculate that SF is an external locomotor condition able to pair, by neural control, the cardiac and muscle oscillator frequencies ( Niizeki et al, 1993 ; Niizeki and Saitoh, 2014 ; Materko et al, 2015 ) and that external condition, in turn, could generate a common frequency inducing synchronization of both signals and which can be recognized as entrainment bands of frequencies.…”