Making a HIIT: Methods for quantifying intensity in high-intensity interval training in schools and validity of session rating of perceived exertion

Correlation is a statistical method used to assess a possible linear association between two continuous variables. It is simple both to calculate and to interpret. However, misuse of correlation is so common among researchers that some statisticians have wished that the method had never been devised at all. The aim of this article is to provide a guide to appropriate use of correlation in medical research and to highlight some misuse. Examples of the applications of the correlation coefficient have been provided using data from statistical simulations as well as real data. Rule of thumb for interpreting size of a correlation coefficient has been provided.

The criterion variables were total weight lifted (Wttot ) determined separately for women and men during BC and KE, and blood lactic acid concentration ([Hla]) determined for a combined female ( N = 10) and male ( N = 10) subset during BC. Subjects performed three separate sets of 4, 8, and 12 repetitions for BC and KE at 65% one-repetition maximum. Rating of perceived exertion for the active muscles (RPE-AM) was measured during the mid and final repetition and RPE for the overall body (RPE-O) during the final repetition. : For both female and male groups across the three sets: (a) RPE-AM ranged from 3.6 to 8.2 for BC and 5.1 to 9.6 for KE and (b) RPE-O ranged from 2.4 to 6.7 for BC and 4.2 to 7.6 for KE. Positive linear regressions ranged from r = 0.79 to 0.91 ( P < 0.01) between Wttot and RPE-AM (mid), RPE-AM (final), and RPE-O for both BC and KE in both sex groupings. A positive ( P < 0.01) linear regression was found between [Hla] and RPE-AM (final) (r = 0.87) during BC. RPE did not differ between women and men at any measurement point within each set for BC and KE. RPE-AM (final) was greater ( P < 0.01) than RPE-O in the three sets of BC and KE. Findings provided concurrent validation of the OMNI-RES to measure RPE for the active muscle and overall body in young recreationally trained female and male weight lifters performing upper- and lower-body resistance exercise.