Vol 8, Issue 3

Sensitivity of Prescribing High-Intensity, Interval Training Using the Critical Power Concept

August 1, 2015 - By 

Authors

Robert W. Pettitt, Minnesota State University, Mankato
Ashley M. Placek, Minnesota State University, Mankato
Ida E. Clark, University of Exeter
Nicholas A. Jamnick, Minnesota State University, Mankato
Steven R. Murray, Colorado Mesa University
International Journal of Exercise Science 8(3): 202-212, 2015.
DOI: 10.70252/WLOO8388

Abstract

The critical power (CP) concept enables the calculation of time to exhaustion (tLIM) for a given power output above CP using the equation of tLIM = W’/(power – CP), where W’ is the curvature constant, and CP is the asymptote for the power-tLIM relationship. The CP concept offers great promise for prescribing high-intensity interval training (HIIT); however, knowledge on the concept’s sensitivity is lacking (i.e., how much of a difference in W’ expenditure is needed to evoke different metabolic responses). We tested if two different power-tLIM configurations expending identical proportions of W’ would evoke different end-exercise oxygen uptake (VO2) and heart rate (HR) values. Five men and five women completed a graded exercise test, 3-min all-out exercise tests, and intervals prescribed to deplete either 70 or 80% of W’ on separate visits. Consistency statistics of intraclass correlation (ICC a), standard error of measure (SEM), and coefficient of variation (CV) were calculated on end-exercise values. End-exercise VO2 were similar for the 3.5- and 5-min bouts, depleting 70% of W’ (ICC a = 0.91, SEM = 3.23 mL·kg-1·min-1, CV = 8.1%) and similar for the 4- and 5-min bouts, depleting 80% of W’ (ICC a = 0.95, SEM = 2.34 mL·kg-1·min-1, CV = 8.1%). No VO2 differences were observed between trials or conditions (p = 0.58). Similarly, HR values (~181 b·min-1) did not differ between trials or conditions (p = 0.45). Use of the CP concept for HIIT prescriptions of different power-tLIM configurations evokes similar end-exercise VO2 values on a given day. Our findings indicate that >10% W’ depletion is necessary to evoke different metabolic responses to HIIT.

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