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Trial registered on ANZCTR


Registration number
ACTRN12621000711819
Ethics application status
Approved
Date submitted
3/05/2021
Date registered
8/06/2021
Date last updated
26/08/2024
Date data sharing statement initially provided
8/06/2021
Type of registration
Prospectively registered

Titles & IDs
Public title
What is the effect of glycerol-, sodium- or glycerol + sodium hyperhydration on physiological and gastrointestinal outcomes during endurance running in the heat?
Scientific title
What is the effect of glycerol-, sodium- or glycerol + sodium hyperhydration on physiological and gastrointestinal outcomes during endurance running in the heat?
Secondary ID [1] 304097 0
None
Universal Trial Number (UTN)
Trial acronym
N/A
Linked study record
N/A

Health condition
Health condition(s) or problem(s) studied:
Dehydration 321766 0
Condition category
Condition code
Diet and Nutrition 319504 319504 0 0
Other diet and nutrition disorders

Intervention/exposure
Study type
Interventional
Description of intervention(s) / exposure
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).
Intervention code [1] 320425 0
Prevention
Intervention code [2] 320717 0
Treatment: Other
Comparator / control treatment
The control condition in this study will require participants to ingest the large bolus of fluid with no nutritional supplement added. The same dosage and timing of fluid ingestion will be used for the control trial as for the intervention trials. The fluid will be artificially sweetened water to match for the sweet taste that glycerol has when orally ingested. Opaque dissolvable tablets filled with an inert substance will be ingested in the same quantity as the sodium trials (i.e., 8 tablets in the sodium trial = 8 tablets in the control trial) in order to blind the participants.
Control group
Placebo

Outcomes
Primary outcome [1] 327370 0
Fluid retention: calculated as the total amount of fluid ingested minus the total amount of urine produced.
Timepoint [1] 327370 0
Fluid retention will be calculated at minute 180 of the trial.
Secondary outcome [1] 394841 0
Gastrointestinal symptoms will be measured using a questionnaire devised from a modified VAS. Participants will rate the severity of upper and lower gastrointestinal symptoms from 0-10. This is a composite secondary outcome.
Timepoint [1] 394841 0
Gastrointestinal symptoms will be continuously monitored throughout the trial at baseline (min 0), min 20, 40, 60, 80, 100, 120, 140, 160, 180.

Eligibility
Key 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.
Minimum age
18 Years
Maximum age
45 Years
Sex
Males
Can healthy volunteers participate?
Yes
Key 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.

Study design
Purpose of the study
Prevention
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Allocation is not concealed.
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Computerised sequence generation.
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?
The people receiving the treatment/s


Intervention assignment
Crossover
Other design features
Phase
Not Applicable
Type of endpoint/s
Efficacy
Statistical methods / analysis
A sample size estimate has been performed using power analysis and sample size software (Power Analysis and Sample Size Software Version 16, Kaysville, Utah, United States) using fluid retention (fluid ingested minus urine output; mL) as the primary outcome variable. The sample size estimate was completed according to an analysis conducted using a three period by three treatment cross-over design using single-factor repeated measures methodology. A sample of 16 participants, measured at three time points, achieves 80% power to detect differences among the means using a Geisser-Greenhouse Corrected F Test with significance accepted at 0.05. According to a recently published study with a similar design to the proposed study, the standard deviation for fluid retention across participants at the same time is assumed to be 225 mL. The pattern of the covariance matrix is to have all correlations equal with a correlation of 0.70 between the first and second time point measurements. The standard deviation of the hypothesised means is 47.14.
Statistical analyses were completed using Stata v17.0 (StataCorp LLC, Texas, United States). Descriptive data are presented as mean ± standard deviation (SD). Linear mixed models were used to analyse data with treatment and time as fixed effects and participant as a random effect. Where significant time, condition or interaction effects were detected, post-hoc comparisons were made using the Benjamini-Hochberg procedure. Mean differences and 95% confidence intervals (CIs) are reported were significant differences between conditions were observed. Statistical significance was accepted at p < 0.05.

Recruitment
Recruitment status
Completed
Date of first participant enrolment
Anticipated
17/06/2022
Actual
17/06/2022
Date of last participant enrolment
Anticipated
1/09/2023
Actual
1/11/2023
Date of last data collection
Anticipated
30/09/2023
Actual
12/12/2023
Sample size
Target
16
Accrual to date
Final
17
Recruitment in Australia
Recruitment state(s)
VIC
Recruitment postcode(s) [1] 37813 0
3000 - Melbourne

Funding & Sponsors
Funding source category [1] 308481 0
University
Name [1] 308481 0
Deakin Unviersity
Country [1] 308481 0
Australia
Primary sponsor type
University
Name
Deakin University
Address
221 Burwood Highway, Burwood, VIC, 3125
Country
Australia
Secondary sponsor category [1] 309325 0
None
Name [1] 309325 0
Address [1] 309325 0
Country [1] 309325 0

Ethics approval
Ethics application status
Approved
Ethics committee name [1] 308434 0
Deakin University Human Research Ethics Committee
Ethics committee address [1] 308434 0
221 Burwood Highway, Burwood, VIC, 3125
Ethics committee country [1] 308434 0
Australia
Date submitted for ethics approval [1] 308434 0
14/04/2021
Approval date [1] 308434 0
03/06/2022
Ethics approval number [1] 308434 0

Summary
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.
Trial website
Trial related presentations / publications
Public notes

Contacts
Principal investigator
Name 110698 0
Dr Amelia Carr
Address 110698 0
Deakin University, Faculty of Health, School of Exercise and Nutrition Sciences, Centre for Sport Research, 221 Burwood Highway, Burwood, VIC, 3125
Country 110698 0
Australia
Phone 110698 0
+61 3 9251 7309
Fax 110698 0
Email 110698 0
[email protected]
Contact person for public queries
Name 110699 0
William Jardine
Address 110699 0
Deakin University, Faculty of Health, School of Exercise and Nutrition Sciences, Centre for Sport Research, 221 Burwood Highway, Burwood, VIC, 3125
Country 110699 0
Australia
Phone 110699 0
+61 429489126
Fax 110699 0
Email 110699 0
[email protected]
Contact person for scientific queries
Name 110700 0
William Jardine
Address 110700 0
Deakin University, Faculty of Health, School of Exercise and Nutrition Sciences, Centre for Sport Research, 221 Burwood Highway, Burwood, VIC, 3125
Country 110700 0
Australia
Phone 110700 0
+61 429489126
Fax 110700 0
Email 110700 0
[email protected]

Data sharing statement
Will individual participant data (IPD) for this trial be available (including data dictionaries)?
Yes
What data in particular will be shared?
All of the individual participant data collected during the trial, after de-identification.
When will data be available (start and end dates)?
Immediately following publication and ending 5 years following main results publication.
Available to whom?
Researchers wishing to access it.
Available for what types of analyses?
Any purpose.
How or where can data be obtained?
Access subject to approvals by the principal investigator or the contact person for public queries:

Principal Investigator: [email protected]
Contact person for public queries: [email protected]


What supporting documents are/will be available?

No Supporting Document Provided



Results publications and other study-related documents

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