Can ten days of heat acclimation training improve temperate-condition rowing performance in national-level rowers?

This study investigated whether heat acclimation (HA) could improve rowing performance in temperate conditions in national-level rowers. Using a parallel-group design, eleven rowers (3 female, 8 male, age: 21±3 years, height: 182.3±6.8cm, mass: 79.2±9.0kg, [Formula: see text]: 61.4±5.1ml·kg·min-1) completed either a HA intervention (HEAT, n = 5) or acted as controls (CON, n = 6). The intervention replaced usual cross-training sessions and consisted of an hour of submaximal cycling or rowing ergometry in either 34±0°C for HEAT or 14±1°C for CON daily over two five-day blocks (10 sessions total), separated by 72h. Participants performed the '10+4' test that consists of 10-min submaximal rowing and a 4-min time-trial (TT) in temperate conditions (20±0°C) before and after the intervention. Heat acclimation following the 10-session intervention was evidenced by large significant (p<0.05) decreases in maximum tympanic temperature (d = -1.68) and rate of perceived exertion (RPE) (d = -2.26), and a large significant increase in sweat loss (d = 0.91). Large non-significant (p>0.05) decreases were seen in average tympanic temperature (d = -3.08) and average heart rate (d = -1.53) in HEAT from session 2 to session 10 of the intervention. Furthermore, a large significant increase was seen in plasma volume (d = 3.74), with large significant decreases in haemoglobin concentration (d = -1.78) and hematocrit (d = -12.9). Following the intervention, large non-significant increases in respiratory exchange ratio (d = 0.87) and blood lactate (d = 1.40) as well as a large non-significant decrease in RPE (d = -1.23) were seen in HEAT during the 10-min submaximal rowing. A large significant decrease in peak heart rate (d = -2.27), as well as a large non-significant decrease in relative [Formula: see text] (d = -0.90) and large non-significant increases in respiratory exchange ratio (d = 1.18), blood lactate concentration (d = 1.25) and power output (d = 0.96) were seen in HEAT during the 4-min TT. This study suggests that a 10-session HA intervention may elicit HA in national-level rowers, with potential to improve 4-min TT performance in temperate conditions.

Hot water immersion; potential to improve intermittent running performance and perception of in-game running ability in semi-professional Australian Rules Footballers?

This study investigated whether hot water immersion (HWI) could heat acclimate athletes and improve intermittent running performance and perception of in-game running ability, during a competitive Australian Rules Football (ARF) season. Fifteen male semi-professional ARF athletes (Mean (SD); age: 22 (3) years, height: 182.3 (6.5) cm, mass: 80.5 (5.1) kg) completed either HWI (HEAT, N = 8, 13 (2) sessions, 322 (69) min exposure, 39.5 (0.3) °C) or acted as a control (CON, N = 7, no water immersion) over 6-weeks. Athletes completed a 30-15 Intermittent Fitness Test pre and post-intervention to assess intermittent running performance (VIFT), with perception of in-game running ability measured. Heat acclimation was determined via change in resting plasma volume, as well as physiological and perceptual responses during HWI. HEAT elicited large PV expansion (mean ± 90% CI: d = 1.03 ± 0.73), large decreases in heart rate (d = -0.89 ± 0.70), thermal sensation (d = -2.30 ± 1.15) and tympanic temperature (d = -1.18 ± 0.77). Large improvements in VIFT were seen in HEAT (d = 1.67 ± 0.93), with HEAT showing a greater improvement in VIFT when compared to CON (d = 0.81 ± 0.88). HEAT also showed greater belief that in-game running ability improved post-intervention (d = 2.15 ± 1.09) compared to CON. A 6-week HWI intervention can elicit heat acclimation, improve perception of in-game running ability, and potentially improve VIFT in semi-professional ARF athletes.

Does Short-Duration Heat Exposure at a Matched Cardiovascular Intensity Improve Intermittent-Running Performance in a Cool Environment?

PURPOSE: To investigate whether a 5-d cycling training block in the heat (35°C) in Australian Rules footballers was superior to exercising at the same relative intensity in cool conditions (15°C) for improving intermittent-running performance in a cool environment (<18°C). METHODS: Using a parallel-group design, 12 semiprofessional football players performed 5 d of cycling exercise (70% heart-rate reserve [HRR] for 45 min [5 × 50-min sessions in total]) in a hot (HEAT, 35°C ± 1°C, 56% ± 9% RH) or cool environment (COOL, 15°C ± 3°C, 81% ± 10% RH). A 30-15 Intermittent Fitness Test to assess intermittent running performance (VIFT) was conducted in a cool environment (17°C ± 2°C, 58 ± 5% RH) before and twice after (1 and 3 d) the intervention. RESULTS: There was a likely small increase in VIFT in each group (HEAT, 0.5 ± 0.3 km/h, 1.5 ± 0.8 × smallest worthwhile change [SWC]; COOL, 0.4 ± 0.4 km/h, 1.6 ± 1.2 × SWC) 3 d postintervention, with no difference in change between the groups (0.5% ± 1.9%, 0.4 ± 1.4 × SWC). Cycle power output during the intervention was almost certainly lower in the HEAT group (HEAT 1.8 ± 0.2 W/kg vs COOL 2.5 ± 0.3 W/kg, -21.7 ± 3.2 × SWC, 100/0/0). CONCLUSIONS: When cardiovascularexercise intensity is matched (ie, 70% HRR) between environmental conditions, there is no additional performance benefit from short-duration moderate-intensity heat exposure (5 × 50 min) for semiprofessional footballers exercising in cool conditions. However, the similar positive adaptations may occur in HEAT with 30% lower mechanical load, which may be of interest for load management during intense training or rehabilitation phases.