Elizabeth Leal-Alfaro1, Brandon Stone2, J. Jay Dawes1

1Oklahoma State University, Stillwater, Oklahoma; 2High Performance Department, The Toronto Blue Jays Baseball Club, Dunedin, Florida

PURPOSE: The purpose of this study was to determine the physiological responses to a 5-day exposure/10-day heat acclimation protocol in elite level boxers. METHODS: Physiological performance data was recorded from thirteen (8 males, 5 females) elite level boxers who underwent a 10-day HA protocol. All sessions were conducted in an environmental chamber (32˚C and 70% RH), at the same time of day. HA sessions occurred on in an every other day fashion, such that odd days were HA sessions (interval based) and ‘even days’ were considered normal sport training (aerobic based) with no HA session conducted. Prior to each session, anthropometric measurements were collected (e.g. height and body mass) and an instrumentation for heart rate (HR) monitoring was utilized, followed by a dynamic warm-up and a HA session or rowing heat stress test (RHST). The RHST occurred 24-hours pre- and post-the first and last HA session. The RHST occurred as follows: 3 minute warm up at self-selected pace followed by 3 “bouts” of 3 minutes maintaining a pace of 10% below their critical power level reached during an initial 3minute all-out effort row. Each bout was separated by 1-minute rest period. Average peak (HRpeak) and relative HR (HRavg) and training load (TLoad) were recorded on a second by second basis, while power output (watts) and pace (meters:minute) were recorded. Each bout was average across 20 second intervals to ensure power output requirements were maintained. RESULTS: Both average heart rate (HRavg) (150.82 ± 9.44 bpm to 129.06 ± 8.00 bpm, p < 0.001) and relative average heart rate (HRrel) (76.06 ± 4.26% to 65.13 ± 4.08%, p < 0.01) were significantly lower from pre- to post-HST. Additionally, training load was also significantly lower from pre to post-heat stress test (31.56 ± 6.55AU to 26.13 ± 4.16AU, p = 0.001). Significant differences in body mass were observed throughout the HST (Session 1 through Session 5, p < 0.01). CONCLUSION: Elite level boxers exhibited improvements in average peak and relative HR (e.g., were lower) for the RHST post HST. There was also a decrease in training load from pre- to post-HST. These results suggest that a 5-day heat acclimation protocol distributed intermittently over a 10-day training period may elicit significant improvements in physiological responses to heat exposure among elite level boxers.

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