Acute Physiological and Perceptual Responses to Decreasing-Distance Versus Constant-Distance HIIT in Elite Male Speed Skaters.

Yang, Z, Peng, F, Lin, J, Zeng, Y, Su, Y, Shi, Y, and Li, W. Acute physiological and perceptual responses to decreasing-distance versus constant-distance HIIT in elite male speed skaters. J Strength Cond Res XX(X): 000-000, 2026-This study investigated the acute effects of a decreasing-distance high-intensity interval training (D-HIIT) strategy vs. a constant-distance HIIT (C-HIIT) protocol on endurance performance, physiological responses, and rating of perceived exertion (RPE) in elite speed skaters. Eighteen Tier-4 male speed skaters were randomized into D-HIIT (1,600, 1,200, 1,200, and 800 m) or C-HIIT (4 × 1,200 m) groups, matched for total distance (4,800 m). Velocity drop rate (VDR), heart rate (HR), blood lactate (BLa), and RPE were monitored. D-HIIT resulted in a significantly shorter total time (381.89 ± 3.55 seconds vs. 393.11 ± 2.93 seconds, p < 0.001) and lower VDR (2.10 ± 0.27% vs. 3.72 ± 0.24%; p < 0.001). D-HIIT also elicited higher peak BLa in the final bout (11.81 ± 0.29 vs. 9.31 ± 0.29 mmol·L -1 , p < 0.001), while terminal RPE was lower than that in C-HIIT (17.22 ± 0.67 vs. 18.22 ± 1.13, p < 0.05). D-HIIT was associated with faster completion, lower velocity drop, higher HR and BLa responses, and lower terminal RPE than C-HIIT under matched external distance. Because RPE did not show a significant Group × Bout interaction, the perceptual findings should be interpreted cautiously. Decreasing-distance high-intensity interval training may be considered as an acute session format for imposing a high physiological stimulus while maintaining manageable perceived exertion, but its mechanisms and long-term training effects require further investigation.