Practical application of a mixed active and passive heat acclimation protocol in elite male Olympic team sport athletes.

To investigate effectiveness and retention of heat acclimation (HA) integrated within an elite rugby sevens team training program, 12 elite male rugby sevens athletes undertook 10 days of mixed active/passive HA across 2 weeks of normal training. Physiological and performance variables were assessed using a sport-specific, repeated high-intensity heat-response test pre-HA; after 5 days (mid-HA) and 10 days (post-HA); and 16 days post-HA (decay). Resting, submaximal, and end-exercise core temperatures were lower at mid-HA (≤-0.26 °C; d ≥ -0.47), post-HA (≤-0.30 °C; d ≥ -0.72), and decay (≤-0.29 °C; d ≥ -0.56), compared to pre-HA. Sweat rate was greater at post-HA compared to pre-HA (0.3 ± 0.3 L·h-1; d = 0.63). Submaximal heart rate (HR) was lower at mid- (-9 ± 4 bpm; d = -0.68) and post-HA (-11 ± 4 bpm; d = -0.90) compared to pre-HA. Mean and peak 6 s power output improved at mid-HA (83 ± 52 W; 112 ± 67 W; d ≥ 0.47) and post-HA (125 ± 62 W; 172 ± 85 W; d ≥ 0.72) compared to pre-HA. Improvements in HR and performance persisted at decay (d ≥ 0.66). The initial 5 days of mixed-methods HA elicited many typical HA adaptations, with an additional 5 days eliciting further thermoregulatory, sudomotor, and performance improvements. Adaptations were well retained after 16 days of normal training, without any further heat stimulus. The trial was retrospectively registered with the Australian New Zealand Clinical Trials Registry (ACTRN12622000732785).

The relationship between physiological and performance variables during a hot/humid international rugby sevens tournament.

To characterise physiological responses to competing in an international rugby sevens tournament played in hot/humid conditions, core temperature (Tc) and Tc predictors were collected from 11 elite men's rugby sevens athletes competing in the Oceania sevens tournament in Suva, Fiji. Tc, body mass change, sweat electrolytes, playing minutes, total running distance, high speed running distance (HSD), psychrometric wet bulb temperature and exertional heat illness symptoms were collected pre, during and post games. Linear mixed-models were used to assess the effect of Tc predictors on post-game Tc, along with differences in Tc across measurement periods. Compared to baseline on both tournament days, mean Tc was higher during all between game (recovery) measures (all d >1.30, p <0.01). On both tournament days, eight athletes reached a post-game Tc >39.0°C, with several athletes reaching >39.0°C during warm-ups. Mean post-game Tc was related to playing minutes, total running distance, HSD, and post warm-up Tc (all p < 0.01). The Tc during warm-ups and games regularly exceeded those demonstrated to be detrimental to repeated sprint performance (> 39°C). Warm-up Tc represents the easiest predictor of post-game Tc to control via time/intensity modulation and the use of appropriate pre- and per-cooling strategies. Practitioners should be prepared to modulate warm-ups and other heat preparation strategies based on likely environmental conditions during hot/humid tournaments.