Hyperhydrating with glycerol: effects on thermoregulation, hydration and athletic performance during specific exergonic exercise in a warm-humid environment

Abstract

We investigated the effects of hyperhydration with glycerol vs. water on athletic performance under hot-humid conditions (30% relative humidity and 36°C). During a 10-day acclimation period, 14 competitive male oarsmen performed 90 minutes of exercise at 260-W. On the eleventh day, athletes hydrated by consuming in 90 minutes a nutrient drink with or without glycerol. After hydration, athletes were tested three times with 250-400-W workloads in 30-W steps, at 15-min intervals. During the 250-400-W tests, athletes rehydrated with water (control and glycerol A groups) or with flavored glycerol solution (glycerol B group). Measurements of total extracellular body water (EBW) by bioelectric impedance analysis indicated a statistically significant increase in water retention (approximately 525 ml) and decreased lactate at aerobic threshold for the glycerol B group compared to the control and glycerol A groups following the exercise tests. The performance on the three 250-400-W tests was stable for glycerol B athletes but decreased for glycerol A and control groups. The 15-W difference observed at the aerobic threshold between glycerol B and control groups was estimated to translate into a 37-m competitive advantage during a 6-min Olympic rowing competition.

Physiological and performance effects of glycerol hyperhydration and rehydration

“…However, one of those seven did show a potentially practical, albeit non‐significant, performance improvement of 9% 10 . One further study showed improved power at the anaerobic threshold with pre‐exercise glycerol hyperhydration and additional glycerol during exercise, as discussed in the next section 55 . Importantly, none of the studies showed a decrement in endurance performance following glycerol hyperhydration.…”

“…Thirteen of the studies discussed in the previous section also investigated the effects of pre‐exercise glycerol hyperhydration on aspects of endurance exercise performance (Tables 2 and 3). Six of the 13 (including one with two series of experiments) showed significant improvements in endurance performance parameters, 7,8,13,16,53,56 while seven did not 10,17,18,20,21,54,55 . However, one of those seven did show a potentially practical, albeit non‐significant, performance improvement of 9% 10 .…”

“… †† Lyons et al., 6 Montner et al., 14 and Dini et al 55 . also gave glycerol during exercise following glycerol‐induced hyperhydration. …”

“…To date, only five studies have employed protocols that include glycerol in beverages consumed during exercise. One of these showed a benefit to anaerobic performance 55 while each of the other four showed one or more significant benefits to thermoregulatory or cardiovascular variables 6,14,57,58 …”

Adaptation to physical training in rats orally supplemented with glycerol

“…Most often, glycerol consumption is evaluated in acute exercise sessions, predominantly observing the hydration aspects (Dini et al 2007;Mehmet and Hüsrev 2011). Further, in a previous study, glycerol supplementation promoted increased use of circulating lipids in rats subjected to 6 weeks of training ).…”