J. Patalano, B. Beltran, E. Escalera, M. Curran, B.W. Wilkins

Gonzaga University, Spokane, WA.

The power-duration relationship describes the fundamental link between average work-rate (power) or velocity (for running) and exercise time. This relationship, and its utility in predicting performance outcomes, has been well described for cycling and running. PURPOSE: This study aimed to establish a rep-rate duration curve using the total reps accomplished during high-intensity interval training (HIIT) type exercise modalities and identify a critical repetition rate (CRR) that delineates sustainable HIIT exercise intensities from those that are unsustainable. METHODS: Six college-age subjects (3 men, 3 women) participated, and completed five study days. The first three study days consisted of the exhaustive time trials for 2, 5, and 15 min (counterbalanced order), where participants were asked to complete as many reps as possible within the allotted time. For each individual, total reps were plotted against time to determine the CRR (slope) and the repetition capacity (Rʹ) above the CRR (intercept) from the regression equation. Subjects returned to the laboratory for two constant rep-rate exercise sessions: one at 5% above and one at 5% below the CRR (rep-rate was established via metronome). Oxygen uptake and heart rate were measured throughout the constant rep-rate trials and venous blood lactate was collected before and after exercise. RESULTS: A robust repetition rate duration relationship exists, with an R2=0.995±0.004 for the total reps over time relationship across all subjects (p<0.001). The CRR was 39.6±10.4 reps/min and the Rʹ was 64.3±11.3 reps. Time to exhaustion during the 5% below constant rep-rate trial was 17.07±0.004 min and was 26.43±0.002 min during 5% above constant rep-rate trials. However, equipment limitations during some of the constant rep-rate data collections restricted interpretation of oxygen uptake kinetics and validation of CRR. CONCLUSION: Similar to endurance cycling and running, there is a robust work rate (rep-rate) duration relationship during HIIT type exercise modalities. However, we were unable to validate the CRR prediction as depicting sustainable vs. unsustainable exercise intensities during the constant rep-rate trials.

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