Purpose: This study examined effects of heat gain, circulatory adjustment to temperature regulation (HR), and [La] consequent to interval (INT) and constant-load (CON) cycling on session RPE (S-RPE). Methods: Male volunteers (N = 10) completed a cycle ergometer V[spacing dot above]O2peak test and then, in a randomized, counterbalanced order, four cycling bouts, including constant load (~45% V[spacing dot above]O2peak) (CON) and interval (8 x 1 min at about 90% V[spacing dot above]O2peak, 1 min between intervals) (INT), in hot (~32.5 WBGT) (HOT) and cool (~21.0 WBGT) (COOL) environments. Trials included a standardized warm-up and cool-down (10 min each: 0 W, 60 rpm). Total external work was equated among all trials, with blood lactate ([La]), heart rate (HR), rectal temperature (Tre), and acute RPE recorded at 10, 13, 17, 21, 25, and 36 min. S-RPE was recorded 20 min after each session. Results: HOT (CON and INT) resulted in significantly (P < 0.05) greater heat gain (Tre), HR, and RPE-O, whereas INT had significantly elevated [La] versus CON (HOT and COOL). HOT yielded significantly higher S-RPE versus COOL for CON (HOT = 5.6 +/- 2.1, COOL = 4.3 +/- 1.3) and INT (HOT = 7.0 +/- 1.9, COOL = 5.1 +/- 2.0). S-RPE was significantly higher for INT/HOT than CON/HOT. Conclusions: Heat gain and cardiac strain (Tre, HR) and [La]) were manipulated with environment and exercise type while holding total work constant. The added strain of HOT was reflected in elevated S-RPE for both CON and INT. S-RPE linkage with [La] was limited to HOT trials, indicating only a loose association. These data indicate that under the conditions of this study, S-RPE is similar to acute RPE in that no single mediator seems universally dominant.
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