THE EFFECT OF HIGH DOSE CREATINE SUPPLEMENTATION ON THERMOREGULATORY ADAPTATION DURING A STANDARD HEAT ACCLIMATION PROTOCOL

Anecdotal reports suggest creatine monohydrate (CrM) causes dehydration and impaired heat tolerance. Empirical evidence of acute CrM supplementation suggests safety, but effects of long-term heat exposure with CrM remains unknown. PURPOSE: To examine heat tolerance after high dose-CrM supplementation during heat acclimation, and to examine thermoregulatory/cardiovascular responses and performance under heat stress after heat acclimation (HA). METHODS: Participants selected for CrM supplementation (n = 9; CrM, 21 ± 2 y, 49.3 ± 7 ml/kg-1/min-1) were pair matched with a control (n = 9; CON, 23 ± 3 y, 49.5 ± 8 ml/kg-1/min-1) (8 M, 10F). Participants performed the Israeli Defense Force Heat Tolerance Test (IDF HTT) (HTT1) and ran at 65% velocity of VO2max (vVO2max) until core temperature of 39.5 °C (HTT2) on subsequent days to assess heat tolerance before (PreHTT) and after (PostHTT) a traditional heat acclimation protocol (HA). CrM supplemented 32 g of CrM and .5 g/kg/bm of carbohydrate during HA and both Post HTT1 and HTT2. CON consumed no supplement. Repeated measures ANOVA, paired t-tests, independent t-tests, and a mixed factor ANOVA were used to compare variables: α = .05 RESULTS: There were no significant differences in rectal temperature for area under the curve during the IDF HTT (CrM pre 4578 ± 48, post 4565 ± 39) (CON pre 4540 ± 51, post 4521 ± 65). Peak heart rate was significantly lower for CrM (pre 147.6 ± 22.8, post 137.6 ± 20.6 bpm, p = 0.008) but not CON (pre 150.1 ± 19.7, post 137.1 ± 17.9, p = 0.055). Change in plasma volume during HTT1 decreased in CrM Post HTT1(pre 45.6 ± 34.8, post -0.8 ± 52.0 mL, p = 0.003) compared to CON (pre 72.7 ± 47.0, post 37.6 ± 51.0 mL, p = 0.683). CrM significantly increased time of exercise during run to 39.5 °C (pre 24.60 ± 4.64, post 28.47 ± 6.10 min, p = 0.036) compared to CON (pre 30.41 ± 3.77, post 33.01 ± 6.58 min, p = 0.24). CONCLUSION: High dose CrM was not detrimental to heat acclimation and improved run time to 39.5 °C. The recommendation not to use CrM during repeated thermal stress should be reconsidered. Potential benefits of CrM to fluid balance and other metabolic mechanisms during repeated exercise-heat stress should be further explored.