Pre- and mid-cooling with ice slurry ingestion: Effects on recovery over 48 h following high-intensity intermittent exercise under temperate conditions.

High-intensity intermittent exercise (HIIE) can elicit substantial thermal and physiological strain even in temperate environments. We examined whether pre-mid cooling using ice slurry ingestion would attenuate thermal strain and enhance physiological and performance recovery over 48h following HIIE under temperate conditions. Seventeen male team-sport athletes completed two HIIEs (four 22.5-min treadmill running quarters (Q1-4) at 4-20 km h-1 interspersed with overground sprints) in a randomized crossover design. Temperate (TEMP; 28°C) or ice slurry (ICE; -1°C) beverages were ingested pre- and mid-HIIE. A 10-s single cycling sprint (SS), repeated cycling sprints (10 × 6 s), root mean square of successive R-R intervals, muscle soreness, and muscle, cardiac, and inflammatory stress biomarkers were measured at pre- and over 48 h post-HIIE. Rectal temperature (Trec) remained lower in ICE from post-ingestion until pre-Q1 (- 0.1 to - 0.3°C; P < 0.01-0.05; d = 0.5-1.1). At Q1, Trec was not significantly different between conditions (P = 0.053; d = 0.51). Trec was similar between conditions in the later quarters (P > 0.1; d ≤ 0.35). Peak SS power (change from baseline) improved in TEMP at 48 h (- 0.7 ± 7.8%; P = 0.001; d = 1.20) but not in ICE (- 4.8 ± 8.9%, P = 1.0; d = 0.02). MP significantly improved at 48 h in both conditions compared to post-exercise (P = 0.037), reaching 1.4 ± 8.1% in TEMP (d = 0.80) and -1.04 ± 7.1% in ICE (d = 0.15), with no between-condition difference (P = 0.072). Muscle soreness score was greater in TEMP (4.5 ± 0.8) than ICE (3.7 ± 1.1) at 24 h (P = 0.033; d = 0.57). Pre-and mid-exercise ice slurry ingestion may attenuate perceived muscle soreness; however, it may delay cycling power recovery following HIIE. Its use as a cooling strategy therefore warrants caution when performance recovery is a priority.