Influence Of Cardiac-locomotor Coupling On Central Hemodynamics: Frequency-domain Analysis

During rhythmic exercises such as jogging or cycling, a phenomenon called "Cardiac-Locomotor Coupling" (CLC), which synchronizes muscle contractions and heart rate, is often observed. PURPOSE: This study aimed to investigate the influence of CLC on central hemodynamics using frequency domain analysis. METHODS: Ten young men participated in a lower limb pedaling exercise. Participants were instructed to synchronize their pedal strokes with the tone during the exercise. An electronic tone was presented at 200 ms, 250 ms, 300 ms, 350 ms, 400 ms, 450 ms, and 500 ms after the R-wave. Each timing was changed every 2 minutes in a random order. ECG, peripheral arterial blood pressure, and electromyography (EMG) of the vastus lateralis muscle were recorded simultaneously. The aortic blood pressure waveform was estimated from the peripheral arterial pressure waveform via the generalized transfer function technique. Power spectra were calculated for each signal, and transfer characteristics (coherence, gain, and phase) were evaluated. RESULTS: Varying the delay time from the ECG R-wave caused fluctuations in coherence between heart rate and lower limb muscle contractions. Coherence was divided into three levels (<0.5, 0.5-0.75, <0.75), and gain was compared across these levels. The gain between lower limb muscle contractions and aortic blood pressure was augmented with increasing coherence between heart rate and lower limb muscle contractions: <0.5 = 33.8 [95% CI: 27.0-40.6], 0.5-0.75 = 56.4 [47.9-64.9], and < 0.75 = 65.4 [56.7-74.2] (F = 18.5, P < 0.0001). CONCLUSIONS: These results suggest CLC impacts central hemodynamics, presumably due to enhancing venous return.