Work

Mixed pre-cooling improves thermal strain but not running performance in female endurance athletes exercising in the heat across the menstrual cycle

Year: 2025

Type: article

Abstract: This study investigated the effect of mixed pre-cooling (cooling vest and ice-slurry) on thermal and cardiovascular strain and performance in unacclimatized females exercising in the heat during menstrual cycle (MC) Phase-1 (low estrogen and progesterone) and Phase-4 (moderate estrogen and high progesterone). In a randomized crossover design, 11 runners completed two trials in each MC Phase: mixed pre-cooling (wearing a cooling vest around the torso for 30 min and ingesting 7.5 g.kg−1 of body mass of ice slurry), and control (equivalent slurry volume at ~20°C without a cooling vest), prior to a 10-km running time trial (TT) in 34°C and 60% relative humidity. Rectal temperature (Tre), heart rate (HR), and perceptual responses were measured throughout the TT. Linear mixed models were fitted to estimate intervention and MC phase effects. Mixed pre-cooling had no effect on HR (1.06 [−0.83, 2.95] beats.min−1; p = 0.272) or TT completion time (−0.23 [−1.32, 0.86] min; p = 0.677) versus control. Tre (−0.21 [−0.34, −0.07] °C; p = 0.003) and thermal sensation (−0.61 [−0.78, −0.44] au; p < 0.001) were significantly lower with mixed pre-cooling compared to control. Rise in Tre (−0.1 [−0.3, 0.0] °C) and thermal sensation were attenuated in MC phase-4 (−0.57 [−0.81, −0.34] au; all p < 0.05). Mixed pre-cooling was effective at attenuating the rise in Tre for a similar work rate, particularly in MC phase-4, where females may experience greater heat thermosensation. However, the magnitude of attenuated Tre does not improve 10-km running performance in the heat, suggesting additional cooling and/or heat mitigation strategies may be required to improve performance.

Source: Temperature

DOI: 10.1080/23328940.2025.2465023