Heat acclimation does not attenuate hepcidin elevation after a single session of endurance exercise under hot condition

Abstract

Purpose We sought to determine the effects of heat acclimation on endurance exercise-induced hepcidin elevation under hot conditions. Methods Fifteen healthy men were divided into two groups: endurance training under hot conditions (HOT, 35 °C, n = 8) and endurance training under cool conditions (CON, 18 °C, n = 7). All subjects completed 10 days of endurance training (8 sessions in total), consisting of 60 min of continuous exercise at 50% of maximal oxygen uptake ( ) under their assigned environment condition. Subjects completed a heat stress exercise test (HST, 60 min exercise at 60% ) to evaluate the exercise-induced thermoregulatory and hepcidin responses under hot conditions (35 °C) before (pre-HST) and after (post-HST) the training period. Results Core temperature during exercise in the post-HST decreased significantly in the HOT group compared to pre-HST ( P = 0.004), but not in the CON group. The HOT and CON groups showed augmented exercise-induced plasma interleukin-6 (IL-6) elevation in the pre-HST ( P = 0.002). Both groups had significantly attenuated increases in exercise-induced IL-6 in the post-HST; however, the reduction of exercise-induced IL-6 elevation was not different significantly between both groups. Serum hepcidin concentrations increased significantly in the pre-HST and post-HST in both groups ( P = 0.001), no significant difference was observed between both groups during each test or over the study period. Conclusion 10 days of endurance training period under hot conditions improved thermoregulation, whereas exercise-induced hepcidin elevation under hot conditions was not attenuated following the training.

The Impact of Heat Acclimation on Gastrointestinal Function following Endurance Exercise in a Hot Environment

“…The present study is placed as a follow-up determination of previous research which reported the effect of HA on the hepcidin response following endurance exercise in a hot environment [ 23 ]. Thus, the subjects and experimental design were thus identical to that study [ 23 ].…”

“…The present study is placed as a follow-up determination of previous research which reported the effect of HA on the hepcidin response following endurance exercise in a hot environment [ 23 ]. Thus, the subjects and experimental design were thus identical to that study [ 23 ]. For determination of sample size, we referred to previous studies that demonstrated large effects of thermoregulatory adaptations (e.g., lower core temperature during endurance exercise in a hot environment) after HA [ 24 , 25 ].…”

“…During each HST, T rec , mean skin temperature (T sk ), heart rate (HR), thermal sensation (TS), and rate of perceived exertion (RPE) were continuously monitored. Before and immediately after each test, body weights were measured to calculate total sweat loss [ 23 ]. After test completion, each subject rested in a chair for 1 h in thermoneutral environment (23 °C, 50% RH).…”

“…Details procedures of the T sk and T rec measurements were reported in our previous study [ 23 ]. The T sk was measured at the chest, arm, thigh, and calf using probe thermometers (NK543 Nikkiso Co., Kanagawa, Japan); the mean skin temperature was calculated as follows following Ramanathan et al [ 26 ]: T sk = 0.3 × (chest + arm) + 0.2 × (thigh + calf).…”

“…The subjects scored their RPE [ 27 ] and TS [ 28 ] at the end of each HST. The sweat loss during the HST was calculated using the changes in body weight before and after exercise [ 23 ].…”