The authors determined, through a meta-analytic approach, whether glycerol-induced hyperhydration (GIH) enhances fluid retention and increases endurance performance (EP) significantly more than water-induced hyperhydration (WIH). Collectively, studies administered 23.9 ± 2.7 mL of fuid/kg body weight (BW) with 1.1 ± 0.2 g glycerol/kg BW, and hyperhydration was measured 136 ± 15 min after its onset. Compared with WIH, GIH increased fluid retention by 7.7 ± 2.8 mL/kg BW (P < 0.01; pooled effect size [PES]: 1.64 ± 0.80, P < 0.01, N = 14). The use of GIH was associated with an improvement in EP of 2.62% ± 1.60% (P = 0.047; PES: 0.35 ± 0.13, P = 0.014, N = 4). Unarguably, GIH significantly enhances fluid retention better than WIH. Because of the dearth of data, the effect of GIH on EP must be further investigated before more definitive conclusions can be drawn as to its ergogenic property.
Goulet is with the McGill Nutrition and Food Science Centre, McGill University Health Centre, Royal Victoria Hospital, Montréal, Québec, Canada H3A 1A1. Aubertin-Leheudre and Dionne are with the Research Centre on Aging, Geriatric Institute, Plante and Dionne, the Dept. of Physiology and Biophysics, and Dionne, also the Faculty of Physical Education and Sports, University of Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4.