Synchronization Of Foot Strike And Cardiac Cycle During Treadmill Running In Non-endurance Trained Individuals

Abstract

Synchronizing cardiac diastole with foot strike during running may maximize the efficiency with which skeletal muscle promotes venous return of blood to the heart. Recent research has found that diastolic stepping results in a lower heart rate (HR) compared to systolic stepping in elite endurance runners. PURPOSE: To assess HR, metabolic responses, and perceived exertion to running when foot strike occurs during either cardiac systole (CS) or cardiac diastole (CD) in non-endurance trained individuals. METHODS: Eight non-endurance trained participants (7 males; Age: 25.3 ± 8 yr; BMI: 23.6 ± 3.2 kg/m2) performed 2, 5-min bouts of treadmill running at a comfortable pace (5.4 ± 0.5 mph) with foot strike occurring during either CD or CS. Participants wore a chest strap that transmitted accelerometer and HR data to a tablet computer with proprietary software. The software generated an auditory beep that was synced with either 45% (CD) or 100% (CS) of each cardiac cycle. Participants were instructed to match their steps to the beeps during both conditions (CD or CS) which were randomized between trials and blinded to the participants. HR, oxygen consumption (VO2), O2-pulse, minute ventilation (VE), and respiratory exchange ratio (RER) were recorded continuously and averaged over the last 3 minutes of each condition. Rating of perceived Exertion (RPE) was recorded during the final minute of each condition. Paired T-tests were used to compare the dependent variables between conditions and all tests were considered significant at the 0.05 level. RESULTS: HR was significantly lower when foot strike occurred during CD compared with CS (163.0±5 vs. 170.1±4 bpm; P < 0.05). Furthermore, there was a trend for O2-pulse to be greater during CD (16.3±1.5 vs. 15.7±1.4 ml/beat; P = 0.07). VE (73.3±5 vs. 74.4±4 l/min), VO2 (35.0±1.3 vs. 35.3±1.2 ml/kg/min), and RPE (10.5±0.7 vs. 10.3±0.8) were not significantly different between CD and CS, respectively. CONCLUSION: During relatively short, steady-state running conditions, synchronization of foot strike with CD results in a significantly lower HR when compared to CS. This may lead to enhanced cardiac filling, which may be beneficial to running performance in non-endurance trained individuals.