Prolonged exercise in the heat provokes several physiological changes due to low glycogen stores and loss of water and electrolytes through sweat. However, it is unclear whether these changes cause an increase in liking of saltiness and, therefore, palatability of an oral rehydration solution (ORS). 

A recent study enrolled Twenty-seven recreationally active participants to complete sensory analysis of an ORS, a traditional sports drink (TS), and a flavored water placebo (PL) at rest and during 60 min (3 × 20-min bouts) of cycling exercise. The standards were 70% age-predicted maximum heart rate (HRmax) at 35.3 (± 1.4)°C and 41 (± 6)% relative humidity. It rated the drinks (using 20-mL beverage samples) before and after every 20 min of exercise based on the liking of sweetness, saltiness, thirst-quenching ability, and overall liking on a nine-point hedonic scale. It also assessed the Hydration status by changes in semi-nude body mass, saliva osmolality (SOsm), and saliva total protein concentration (SPC). 

The study found-

• After 60 min of exercise, participants lost 1.36 ± 0.39% (mean ± SD) of body mass with an increase in SOsm and SPC.
• At all time points, liking of sweetness, saltiness, thirst-quenching ability, and overall liking was higher for the TS and PL than the ORS.
• After 60 min of exercise, the ORS′s saltiness, liking, and thirst-quenching ability boosted than before exercise.
• Predictors of overall liking also changed with pre-exercise ratings mostly determined by liking of sweetness, saltiness, and thirst-quenching ability. In contrast, only liking of saltiness predicted overall liking post-exercise. 

This study explains a possible appearance of a hedonic shift during exercise in which the sense of saltiness becomes the most significant predictor of overall liking. 

Thus, these finding regards ORS as a valuable means of hydration during the latter stages of prolonged and/or intense exercise in the heat.

Kitson O, Rutherfurd-Markwick K, Foskett A, Lee JKW, Diako C, Wong M, Ali A. Sensory Perception of an Oral Rehydration Solution during Exercise in the Heat. Nutrients. 2021 Sep 23;13(10):3313. doi: 10.3390/nu13103313. PMID: 34684314; PMCID: PMC8537885.