What is the effect of glycerol-, sodium- or glycerol + sodium hyperhydration on physiological and gastrointestinal outcomes during endurance running in the heat?

Status

Completed

Phases

Unknown

Study type

Interventional

Source

ANZCTR

Registry ID

ACTRN12621000711819

Acronym

N/A

Enrollment

Registered

2021-06-08

Start date

2022-06-17

Completion date

2023-11-01

Last updated

2024-09-02

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

None listed

Brief summary

Exercise performance is impaired in hot conditions compared with temperate conditions. During exercise in such thermally stressful conditions, fluid loss through sweat production to liberate heat from the body is accelerated, which can adversely impact cardiovascular and thermoregulatory function and ultimately hinder exercise performance. To increase the total fluid pool available for sweat production, ingestion of nutritional aids such as glycerol and sodium prior to exercise may increase total body water above normal body water levels (i.e., euhydration) prior to exercise, which is known as hyperhydration. This topic requires further investigation to determine if hyperhydration is a viable preparation strategy for endurance running in hot conditions. The hypothesis for this study is that the combined ingestion of glycerol and sodium will result in a significantly greater fluid retention than that of glycerol or sodium ingested separately.

Interventions

Participants ingest 1 of 4 nutritional supplements with a large bolus of fluid (25 millilitres per kilogram of body mass) before completing 90 min of treadmill exercise in hot conditions. The 4 nutritional interventions are: - glycerol (1.2 grams per kilogram of body mass) - sodium (7.5 grams per litre of fluid ingested) - glycerol + sodium (1.2 grams per kilogram of body mass + 7.5 grams per litre of fluid ingested) - control (this will be the large bolus of fluid without any nutritional supplement). The sodium will be orally consumed using opaque coloured, dissolvable tablets to protect from the salty taste. Glycerol will be orally mixed in with the large bolus of fluid. The fluid bolus will be artificially sweetened water (using a sugar-free additive) made according to the manufacturers instructions. All bolus' will be ingested under supervision by the research team in order to monitor adherence. The wash-out period between trials will be at least seven days. Each intervention will be orally ingested once only in 4 equal portions over a 60 minute period (i.e., minute 0, 20, 40 and 60).

Study design

Allocation

Randomised controlled trial

Intervention model

Crossover

Primary purpose

Prevention

Masking

Blinded (masking used) (Subject)

Eligibility

Sex/Gender

Male

Age

18 Years to 45 Years

Healthy volunteers

Yes

Inclusion criteria

The inclusion criteria for this study is: Trained males or females, aged 18-45 years. To be classified as ‘trained’, participants must be completing running-based training equal to or greater than 3 times per week and equal to or greater than 5 hours per week as per published criteria for participants completing exercise-based studies. Naturally menstruating females will need to be classified as ‘eumenorrheic’ (i.e., having 9 or more menstrual cycles in the last 12 months and having a menstrual cycle that ranges between 21 and 35 days in length). For oral contraceptive users. Females using an oral contraceptive will need to have been using the same oral contraceptive for the previous three months.

Exclusion criteria

Exclusion criteria also includes any abnormal renal function, use of diuretics or creatine in the previous eight weeks as these factors can affect the body’s fluid retention capability. Participants that have previously suffered from heat illness and those that have an impairment that affects thermoregulation will also be excluded. Participants will be excluded if they answer ‘Yes’ to any of the first six questions in stage one of the attached Exercise and Sport Science Australia (ESSA) pre-screening tool. Participants will also complete stage 2 of the ESSA pre-screening tool, those that have multiple (equal to or greater than 2) risk factors, will be asked to seek medical advice before participating in this project. Participants must not have sustained a lower limb injury in the last six months and have no current injury that will impact their ability to complete the exercise protocol in the study. Participants will also be excluded if they have a history of migraines, chronic headaches, liver disease as it is recommended that these populations avoid glycerol ingestion. Participants who are allergic to the nutritional aids to be used in the study (e.g., glycerol and/or sodium chloride) will also be excluded.

Outcome results