| Purpose. The purpose of this study was to determine the effects of glycerol ingestion on fluid balance and cardiovascular hemodynamics at rest and during exercise at high altitude.; Methods. Twelve male subjects (mean age ± SD = 32.8 ± 7.5 yr) volunteered for this study. Each subject completed 4 trials in a randomized design: (a) 6% carbohydrate/electrolyte (CHO) at 5,000 ft, (b) 5% glycerol + CHO (GLY) at 5,000 ft, (c) CHO at 12,000 ft, and (d) GLY at 12,000 ft. Subjects consumed 30 ml/kg LBM of each drink in 5 equal volumes at minutes 0, 30, 60, 90 and 120. At min 150, resting heart rate (HR), cardiac output (Q), plasma volume change (ΔPV) and stroke volume (SV) were obtained. Also at min 150, total free water clearance (CH2O) and osmolar clearance (COSM) were calculated. Exercise HR, Q, ΔPV and SV were obtained while the subject cycled at a workload corresponding to 50% of their 5,000 ft ventilatory threshold (VT).; Results. There were no significant differences between GLY and CHO for HR, Q, ΔPV or SV (p > .05). There were significant differences between GLY and CHO on CH2O and COSM (p < .001). The means for the drink main effects on CH2O were 33.9 ± 12.92 ml/min and 10.11 ± 9.16 ml/min for CHO and GLY, respectively. For COSM, the means for the drink main effects were 18.25 ± 4.08 ml/min and 27.93 ± 5.49 ml/min for CHO and GLY, respectively. No significant interactions were found. In addition, there was a fluid retention of 646.7 ± 294.1 ml during the GLY trials, compared to only 11 ml for CHO. Also, there was a lack of acute mountain sickness (AMS) symptoms corresponding to the fluid retention.; Conclusions. The results confirm that GLY is superior to CHO in reducing CH2O, regardless of altitude. We were able to demonstrate a hyperhydration without symptoms of acute mountain sickness (AMS), following glycerol ingestion at 12,000 ft. Several previous studies have reported associations between fluid retention and AMS. The inconsistencies between our results and previous research warrant further investigation. |
