In a recent study published within the journal Nutrients, researchers in the US evaluated the impacts of various carbohydrate (CHO) and sodium (Na) content in sports drinks (SD) and oral rehydration solutions (ORS) for post-exercise rehydration.
Study: Post-Exercise Rehydration in Athletes: Effects of Sodium and Carbohydrate in Industrial Hydration Beverages. Image Credit: GaudiLab / Shutterstock
Inadequate fluid intake during sports may cause dehydration, impair performance, and increase the probability of warmth sickness. Proper rehydration is critical between training sessions and tournaments, especially during temporary recuperation periods. Rehydration involves stomach emptying, intestinal fluid absorption, and fluid retention to replenish bodily fluid compartments. Studies have indicated that individuals must devour 125% to 150% of their lost volume to rehydrate after exercise. Rehydration beverages, similar to sports drinks, contain carbohydrates and sodium. The impact of various sodium and carbohydrate content on rehydration beverages is unclear and requires further research.
In regards to the study
In the current randomized, double-blinded, and placebo-controlled clinical trial, researchers compared beverages with varied CHO and Na content inside sports drinks consumed for rehydration following exercise amongst athletes. The researchers hypothesized that higher sodium and lower carbohydrate content would promote the best rehydration.
The study aimed to evaluate the completeness of rehydration after 3.5 hours of beverage administration. The researchers compared water (W) as a placebo to an oral-rehydrating solution (45.0 mmol/L sodium and a pair of.5% carbohydrates) and an everyday sports drink (18.0 mmol/L sodium and 6.0% carbohydrates). The team expected that rehydrating the ORS and SD would surpass the W.
The study included physically fit male individuals aged between 18 and 30 years who engaged frequently in moderate-strong exercise. Females weren’t included to evade the potential confounding influence of estrogen levels on the retention of water, which can influence rehydration comparisons within the testing duration. The study participants were healthy, without metabolic, cardiovascular, renal, or endocrine illness or malfunction, and followed a uniform weight-reduction plan. The height oxygen intake was 50 mL/kg/minute.
Participants exercised during a 90-minute session consisting of three 25-minute periods of intermittent-intensity exercise performed indoors after a 2.0-minute warm-up. Sweat samples were collected throughout the second 25-minute phase of activity, and sodium concentration was determined to estimate whole-body sodium loss during exercise. No fluids were administered throughout the exercise-dehydration interval to attain a 2.5% to three.0% drop in body mass.
Participants were weighed and rested for 45 minutes before consuming a beverage volume equal to 100% of body mass loss. Beverages were consumed in six aliquots over 1.0 hours after the study. The study used urine samples to guage fluid retention and the amount of beverages provided to participants for rehydration. The mass of urine voided at minutes 30, 60, 135, and 210 following beverage administration was used to guage fluid retention. After collecting urine, body mass was assessed at 60 and 210 minutes.
A transportable sodium analyzer was used to check sodium levels in sweat. Sodium consumption during post-exercise rehydration was determined by multiplying the sodium content of the beverage by the quantity of fluid swallowed. The drinks were purple-colored, grape-flavored, and served in opaque cups.
Subjects were provided similar meals for twenty-four hours and questioned about physical exertion and nutrition before each experiment to determine a consistent weight-reduction plan with equivalent calorie and salt intake. Exercise was performed on treadmills, stationary bikes, and elliptical machines; the usage sequence varied across individuals but was consistent across all trials. Every 25-minute phase included specific intervals of jogging (7.0 mph), running (10 mph), and walking (3.0 mph) or exercising with elliptical machines or cycles with equivalent intensity. A pilot study was conducted to guage how sodium balance influenced rehydration completion.
In total, 20 individuals participated in three trials performed over 3.5 hours. The ORS and SD had similar and better %FR at 3.5 hours, with the ORS having increased suppression of urine production in the primary 60 minutes in comparison with the W. By 3.5 hours, the ORS and SD promoted greater rehydration than the W, however the pattern of rehydration early in recovery favored the ORS.
The water placebo showed more excretion of urine on the 30-minute timepoint than the SD trial, and at 60 minutes, it promoted more significant fluid loss in comparison with ORS and SD. By 135 minutes, W induced greater fluid loss in comparison with the ORS. The statistically significant interactions observed between 30- and 60-minute collections for SD versus the oral-rehydrating solution indicated that the ORS suppressed urine secretion to a greater extent than SD.
In comparison with pre-exercise levels, there was a statistically significant reduction in body mass post-exercise. Non-significant differences were observed between the treatments for body mass in absolute terms. Nonetheless, significant body mass alterations were observed between 60 and 210 minutes post-treatment, indicating that higher sodium may profit hydration maintenance. The variation coefficient for the mean sodium content in sweat was 10%, indicating that improving sodium balance improves rehydration.
Overall, the study findings showed that beverages with higher sodium and lower cholesterol content promoted higher rehydration completeness. The ORS and sports drinks rehydrated the athletes to a greater extent than the placebo. The ORS was 32% more practical than the water placebo, indicating that carbohydrates may offset the consequences of lower sodium content. The ORS also promoted a more rapid recovery, as rapidly absorbed beverages with sodium and glucose osmolytes kept plasma osmolality higher and reduced urine excretion.