December Issue 2023

Secondly, author Mohammad Fayiz AbuMoh’d designed a randomized controlled trial to determine the influence of
isotonic sports drink ingestion during exercise on endurance capacity and aldosterone response.6 Participants included
twelve main endurance athletes separated into one of three experimental trials – ingesting a sports drink, water, and or
neither option. Each trial had participants run 3000m with an hour recovery and time to administer an exhaustion test as
a way of measuring differences in aldosterone responses before and after the run. The results indicated significant
differences in heart rate which was lower in participate who consumed the sports drink. Furthermore, lower levels of
aldosterone, blood glucose, and sodium were shown in the sports drink group. However, endurance capacity was
significantly greater with the sports drink group compared to water. Thus, isotonic sports drink provide optimal
endurance capacity and maintains aldosterone levels more effectively than hypertonic, hypotonic sports drinks and
water.6 Similarly, to examine the changes in central hydration during continuous exercise, Rowlands et al analyzed the
hydrating effects of hypertonic, isotonic, and hypotonic sports drinks containing carbohydrates and electrolytes
compared to non-carbohydrate-electrolyte drinks and regular water.3 The researchers conducted a meta-analysis
retrieving relevant literature on hypotonic, isotonic, and hypertonic solutions and water. Inclusion studies had to
compare the effect of how the solutions formulated to different osmolality by altering carbohydrate concentrations
and/or electrolyte concentrations. Drinks had to have been consumed orally in all trials with an ingestion rate of ≥ 1 mL
min-1. Hydration was evaluated with plasma volume change from stable resting baseline (central hydration = dPV) with >
1 during exercise samples. Exclusion criteria were studies that had uninterpretable treatment with regard to outcome
measures, subjects dehydrated prior to exercise, or ingested drinks contained protein.
The researchers systematically reviewed randomized crossover trials that
were either double blinded or single blinded. Recruitment included elite
cyclists, runners, triathletes, and recreational active adults. All studies
provided participants with a beverage prior to exercise between 100-813
mL. Thirteen trials supplied servings of about 100-407 mL at 15-min
intervals, six trials at 10 min intervals, six trials at 20 intervals, and two
trials at 30 min intervals. The studies had variables of heat index, average
drink ingestion rate, metabolic rate, total electrolyte, adjusted drink
osmolality, ingested drink osmolality, and total carbohydrate sectioned
into fructose, glucose, and sucrose g/vol. The results showed that metabolic
rate was associated with a lower dPV leading to a larger effect with isotonic
drinks. In addition, increasing the drink ingestion rate lowered the mean
dPV when hypertonic drinks were consumed from the second tertial
Timebin. However, ingesting hypotonic drinks had no impact on dPV early
in exercise. Lastly, the effect of adjusting carbohydrate composition for
intestinal osmolality on dPV was to increase the effect-size difference and
compatibility between each treatment solution. For every 100 mOsM kg-1
increase in ingested osmolality, dPV decreased by -1.1%. Therefore,
adjusting for the effect of carbohydrate digestion reduced dPV to -0.3%
with a 100 mOsM kg-1 increase. Overall, the data gathered from Rowlands
et al demonstrated that hypotonic carbohydrate drinks ingested during
continuous exercise was more likely to maintain central hydration (dPV)
compared to isotonic, hypertonic carbohydrate drinks and noncarbohydrate
drinks.3
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