The Effects Of A Counterpulsation Auditory Prompt On Hemodynamics And Metabolism During Endurance Running

Abstract

Recent studies in elite runners suggest that cardiolocomotor synchronization, when step rate and heart rate naturally occur with a 1:1 ratio, can lead to hemodynamic advantages of counterpulsation when the foot strikes occur during the diastolic phase of the cardiac cycle. PURPOSE: Healthy non-elite runners were studied to investigate the hemodynamic and metabolic responses to prolonged counterpulsation by prompting individuals to step during the diastolic phase of their cardiac cycles during endurance running. We hypothesized that an auditory prompt that elicited counterpulsation would result in a lower heart rate, pulse pressure, respiratory exchange ratio (RER), ventilation and blood lactate, and higher oxygen consumption and blood glucose compared to an auditory prompt that did not elicit counterpulsation. METHODS: Fifteen healthy subjects (8 male, 7 female) completed two single-blinded sessions of 20-minutes of continuous treadmill running at an intensity of 60-80% of VO2max in randomized order: 1) with an auditory prompt adaptive to the subject’s real-time heart rate and stepping phase to guide diastolic stepping, and 2) with a non-adaptive, constant frequency auditory prompt set at each subject’s natural step rate. Heart rate and indirect calorimetry were measured continuously throughout exercise followed by 10 minutes of sedentary recovery. Finger pricks for blood lactate and glucose were done every five minutes during exercise and every two minutes during recovery. Blood pressure was measured pre- and post-exercise and post-recovery. RESULTS: The adaptive auditory prompt successfully guided runners to step in diastole >75% of the steps and resulted in a significantly lower pulse pressure following the post-exercise recovery compared to the non-adaptive prompt (31 ± 2 vs. 36 ± 3 mmHg, p < 0.05). We also observed trends in lower heart rate (2-6 beats/min) and higher blood glucose (0.1-0.3 mM) during exercise guided by the adaptive auditory prompt compared to the non-adaptive prompt. No differences were observed in the other variables. CONCLUSION: Counterpulsation, through prompted cardiolocomotor synchronization, may have hemodynamic advantages during and after endurance running in a healthy recreationally active population.