Audrey Asselin

Pre-exercise hyperhydration-induced bodyweight gain does not alter prolonged treadmill running time-trial performance in warm ambient conditions.

This study compared the effect of pre-exercise hyperhydration (PEH) and pre-exercise euhydration (PEE) upon treadmill running time-trial (TT) performance in the heat. Six highly trained runners or triathletes underwent two 18 km TT runs (~28 °C, 25%–30% RH) on a motorized treadmill, in a randomized, crossover fashion, while being euhydrated or after hyperhydration with 26 mL/kg bodyweight (BW) of a 130 mmol/L sodium solution. Subjects then ran four successive 4.5 km blocks alternating between 2.5 km at 1% and 2 km at 6% gradient, while drinking a total of 7 mL/kg BW of a 6% sports drink solution (Gatorade, USA). PEH increased BW by 1.00 ± 0.34 kg (P < 0.01) and, compared with PEE, reduced BW loss from 3.1% ± 0.3% (EUH) to 1.4% ± 0.4% (HYP) (P < 0.01) during exercise. Running TT time did not differ between groups (PEH: 85.6 ± 11.6 min; PEE: 85.3 ± 9.6 min, P = 0.82). Heart rate (5 ± 1 beats/min) and rectal (0.3 ± 0.1 °C) and body (0.2 ± 0.1 °C) temperatures of PEE were higher than those of PEH (P < 0.05). There was no significant difference in abdominal discomfort and perceived exertion or heat stress between groups. Our results suggest that pre-exercise sodium-induced hyperhydration of a magnitude of 1 L does not alter 80–90 min running TT performance under warm conditions in highly-trained runners drinking ~500 mL sports drink during exercise.

Intestinal temperature does not reflect rectal temperature during prolonged, intense running with cold fluid ingestion.

It is generally assumed that intestinal temperature (Tint), as measured with a telemetric pill, agrees relatively well with rectal temperature (Trec) during exercise. However, whether Tint reflects Trec during prolonged, intense and continuous exercise when cold fluids are consumed is unknown. Therefore, we compared Trec and Tint during a half-marathon during which cold water was ingested to prevent bodyweight (BW) losses >2%. Nine endurance athletes (age 30  ±  5 years) underwent a 21.1 km running time-trial (TT) in the heat (~30 °C and 44% RH) while BW losses were maintained to ~1% with continuous cold (4 °C) water provision. Tint and Trec were monitored throughout the TT. Hypohydration level, TT time and fluid intake were 1.2  ±  0.4% BW, 93.2  ±  9.9 min and 2143  ±  264 ml, respectively. Trec was systematically higher than Tint by 0.25 °C (95% CI: 0.14-0.37 °C). Tint and Trec showed an excellent relative (r = 0.90, p < 0.01), but poor absolute agreement as reflected by a 95% limit of agreement of ±1.07 °C and a standard error of measurement of ±0.39 °C. In conclusion, Tint does not mirror Trec during prolonged, intense running with cold fluid ingestion and, therefore, these measures should not be used interchangeably under this scenario.

Measurement of sodium concentration in sweat samples: comparison of 5 analytical techniques

Sweat sodium concentration (SSC) can be determined using different analytical techniques (ATs), which may have implications for athletes and scientists. This study compared the SSC measured with 5 ATs: ion chromatography (IChr), flame photometry (FP), direct (DISE) and indirect (IISE) ion-selective electrode, and ion conductivity (IC). Seventy sweat samples collected from 14 athletes were analyzed with 5 instruments: the 883 Basic IC Plus (IChr, reference instrument), AAnalyst 200 (FP), Cobas 6000 (IISE), Sweat-Chek (IC), and B-722 Laqua Twin (DISE). Instruments showed excellent relative (intraclass correlation coefficient (ICC) ≥ 0.999) and absolute (coefficient of variation (CV) ≤ 2.6%) reliability. Relative validity was also excellent between ATs (ICC ≥ 0.961). In regards to the inter-AT absolute validity, compared with IChr, standard error of the estimates were similar among ATs (2.8-3.8 mmol/L), but CV was lowest with DISE (3.9%), intermediate with IISE (7.6%), and FP (6.9%) and highest with IC (12.3%). In conclusion, SSC varies depending on the AT used to analyze samples. Therefore, results obtained from different ATs are scarcely comparable and should not be used interchangeably. Nevertheless, taking into account the normal variability in SSC (∼±12%), the imprecision of the recommendations deriving from FP, IISE, IC, and DISE should have trivial health and physiological consequences under most exercise circumstances.

Comparison of Sodium Chloride Tablets-Induced, Sodium Chloride Solution-Induced, and Glycerol-Induced Hyperhydration on Fluid Balance Responses in Healthy Men

Abstract Savoie, FA, Asselin, A, and Goulet, EDB. Comparison of sodium chloride tablets–induced, sodium chloride solution–induced, and glycerol-induced hyperhydration on fluid balance responses in healthy men. J Strength Cond Res 30(10): 2880–2891, 2016—Sodium chloride solution–induced hyperhydration (NaCl-SolIH) is a powerful strategy to increase body water before exercise. However, NaCl-SolIH is associated with an unpleasant salty taste, potentially dissuading some athletes from using it and coaches from recommending it. Therefore, we evaluated the hyperhydrating potential of sodium chloride tablets–induced hyperhydration (NaCl-TabIH), which bypasses the palatability issue of NaCl-SolIH without sacrificing sodium chloride content, and compared it to NaCl-SolIH and glycerol-induced hyperhydration (GIH). Sixteen healthy males (age: 21 ± 2 years; fat-free mass (FFM): 65 ± 6 kg) underwent three, 3-hour long passive hyperhydration protocols during which they drank, over the first 60 minutes, 30-ml·kg−1 FFM of an artificially sweetened solution. During NaCl-TabIH, participants swallowed 7.5, 1 g each, sodium chloride tablets with every liter of solution. During NaCl-SolIH, an equal quantity of sodium chloride tablets was dissolved in each liter of solution. With GIH, the glycerol concentration was 46.7 g·L−1. Urine production, fluid retention, hemoglobin, hematocrit, plasma volume, and perceptual variables were monitored throughout the trials. Total fluid intake was 1948 ± 182 ml. After 3 hour, there were no significant differences among treatments for hemoglobin, hematocrit, and plasma volume changes. Fluid retention was significantly greater with NaCl-SolIH (1150 ± 287 ml) than NaCl-TabIH (905 ± 340 ml) or GIH (800 ± 211 ml), with no difference between NaCl-TabIH and GIH. No differences were found among treatments for perceptual variables. NaCl-TabIH and GIH are equally effective, but inferior than NaCl-SolIH. NaCl-TabIH represents an alternative to hyperhydration induced with glycerol, which is prohibited by the World Anti-Doping Agency.

Sodium-induced hyperhydration decreases urine output and improves fluid balance compared with glycerol- and water-induced hyperhydration

Before 2010, which is the year the World Anti-Doping Agency banned its use, glycerol was commonly used by athletes for hyperhydration purposes. Through its effect on osmoreceptors, we believe that sodium could prove a viable alternative to glycerol as a hyperhydrating agent. Therefore, this study compared the effects of sodium-induced hyperhydration (SIH), glycerol-induced hyperhydration (GIH) and water-induced hyperhydration (WIH) on fluid balance responses. Using a randomized, double-blind and counterbalanced protocol, 17 men (21 ± 3 years, 64 ± 6 kg fat-free mass (FFM)) underwent three 3-h hyperhydration protocols during which they ingested, over the first 60-min period, 30 mL/kg FFM of water with (i) an artificial sweetener (WIH); (ii) an artificial sweetener + 7.45 g/L of table salt (SIH); or (iii) an artificial sweetener + 1.4 g glycerol/kg FFM (GIH). Changes in body weight (BW), urine production, fluid retention, hemoglobin, hematocrit, plasma volume, and perceptual variables were monitored throughout the 3-h trials. After 3 h, SIH was associated with significantly (p < 0.05) lower hemoglobin, hematocrit (SIH: 43.1% ± 2.8%; GIH: 44.9% ± 2.4%), and urine production, as well as greater BW, fluid retention (SIH: 1144 ± 294 mL; GIH: 795 ± 337 mL), and plasma volume (SIH: 11.9% ± 12.0%; GIH: 4.0% ± 6.0%) gains, compared with GIH and WIH. No significant differences in heart rate or abdominal discomfort were observed between treatments. In conclusion, our results indicate that SIH is a superior hyperhydrating technique than, and proves to be a worthwhile alternative to, GIH.