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Trial registered on ANZCTR

Registration number

ACTRN12626001216303p

Ethics application status

Submitted, not yet approved

Date submitted

15/09/2026

Date registered

1/10/2026

Date last updated

1/10/2026

Date data sharing statement initially provided

1/10/2026

Type of registration

Prospectively registered

Titles & IDs

Public title

Assessing the Influence of Age on Fluid Consumption Post Exercise Induced Dehydration In Healthy People aged 12 and over

Scientific title

Assessing the Influence of Age on Water and Non-Nutritive Sweetened Fluid Consumption Post Exercise Induced Dehydration

Additional trial identifiers [1]

Nil

Universal Trial Number (UTN)

Trial acronym

Related trial records

Health condition

Health condition(s) studied:

Dehydration

Condition category

Condition code

Diet and Nutrition

Other diet and nutrition disorders

Intervention/exposure

Study type

Interventional

Description of the intervention or exposure

The study uses a randomised cross-over design. Participants have their hydration status confirmed with a variety of hydration assessments: blood plasma osmolality (direct and indirect), urine osmolality, saliva osmolality, urine specific gravity, BUN-Creatinine ratio, and urine colour. Nude body mass is recorded, and baseline physiological measures of core temperature, heart rate and blood pressure are measured. Participants are moved into a climate-controlled chamber (40 degrees C, 10% RH) to complete self-selected bouts of exercise on a cycle ergometer until they lose 2% of their starting body mass. Exercise intensity is self-selected, with a minimum intensity prescribed of 90 BPM. Participants are then moved into a thermoneutral environment for 120 minutes. The primary outcome is fluid consumed during the 120-minute rehydration period; the fluid provided is randomised to be either water or water with an added non-nutritive sweetener. At the end of the 120 minutes, hydration assessments are repeated. We are intested to observe if there is an effect of age on fluid consumption during a dehydrated state. All sessions are face-to-face at the Thermal Ergonomics Laboratory (The University of Sydney). The experimental sessions will last 5 hours in total, with two sessions and one familiarity session (one hour), totalling 11 hours. There will be at least 72 hours between each trial.

Adherence will be recorded via session completion rates by a member of the research team; dropouts will be reported to the PI.
The study is overseen by Professor Ollie Jay (Principal Investigator). Dr Grant Lynch and Dr Tim English are researchers on the project, and Jake McCahon is the student researcher (PhD Candidate) responsible for data collection. All researchers are members of The Heat and Health Research Centre and have experience within the field of thermoregulation and human physiology.

Intervention code [1]

Treatment: Other

Description of the comparator or control

Participants serve as their own control as they repeat each experimental trial, for example a participant will complete one trial with water and one trial with the non-nutritive sweetener.

Control group

Active

Outcomes

Primary outcome [1]

Quantity of fluid consumed

Timepoint [1]

Post 120-minute rehydration period

Secondary outcome [1]

Onset of fluid consumption

Timepoint [1]

Measured during the 120 minute rehydration period

Eligibility

Key inclusion criteria

Between the ages of 12 and 14, and over the age of 18, have a body mass index equal to or less than 35kg/m2, are nonsmokers, are medically fit, and speak English to provide informed consent. They are able to understand the demands of the protocol, have had any questions answered, and have voluntarily signed the participant consent form prior to any study procedures

Minimum age

12 Years

Maximum age

No limit

Sex

Both males and females

Healthy volunteers

Yes

Key exclusion criteria

Exclusions include the following:

• BMI above 35kg/m2 or below 18.5kg/m2
• People aged between 14 and 18 years of age
• Current smoker
• Musculoskeletal limitations that result in an inability to perform the exercise protocol.
• Inability to provide informed consent.
• History of active or recently treated cancer (not including non-melanoma skin cancers), cardiovascular disease, diabetes, renal disease, endocrine abnormalities, anaemia, abnormal thyroid function or metabolic syndrome.
• Uncontrolled hypertension/hypotension, significant cognitive impairment, psychiatric disorders, peripheral neuropathy or electrolyte disorders.

• Participants taking medication that alter thermoregulatory responses including the following:
o Anticholinergic agents, Beta Blockers, Alpha-agonists, Calcium Channel Blockers, Diuretics, SSRis, SNRis, Antipsychotics, Stimulants, Hormonal Agents (such as HRT), Thyroid medications, endocrine agents

• Participants taking medications that alter thirst response including the following:
o SGLT inhibitors, Lithium, opioids, ACE inhibitors

• Participants taking recreational or illicit substances such as:
o MDMA, cocaine, methamphetamine, cannabis

Study design

Purpose of the study

Treatment

Allocation to intervention

Randomised controlled trial

Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)

Central randomisation. The randomisation takes place by a person independent of the researcher collecting data, after participant enrolment and prior to the experimental session.

Methods used to generate the sequence in which subjects will be randomised (sequence generation)

Computer-generated random sequence (Python Script)

Masking / blinding

Open (masking not used)

Who is / are masked / blinded?

Intervention assignment

Crossover

Other design features

Phase

Not Applicable

Type of endpoint/s

Statistical methods / analysis

Recruitment

Recruitment status

Not yet recruiting

Date of first participant enrolment

Anticipated

30/10/2026

Actual

Date of last participant enrolment

Anticipated

1/12/2027

Actual

Date of last data collection

Anticipated

15/12/2027

Actual

Sample size

Target

Accrual to date

Final

Recruitment in Australia

Recruitment state(s)

NSW

Funding & Sponsors

Funding source category [1]

Government body

Name [1]

National Health and Medical Research Council (NHMRC)

Address [1]

Country [1]

Australia

Primary sponsor type

University

Name

The University of Sydney

Address

Country

Australia

Secondary sponsor category [1]

None

Name [1]

Address [1]

Country [1]

Ethics approval

Ethics application status

Submitted, not yet approved

Ethics committee name [1]

The University of Sydney Human Research Ethics Committee

Ethics committee address [1]

https://www.sydney.edu.au/research/research-integrity-and-ethics.html

Ethics committee country [1]

Australia

Date submitted for ethics approval [1]

12/05/2026

Approval date [1]

Ethics approval number [1]

Summary

Brief summary

Thirst is the primary mechanism to maintain hydration status in people; a loss of body mass (sweating) should trigger fluid consumption. There is evidence to indicate that age may alter the effect of thirst on fluid consumption. Additionally, there is data to suggest that changing the fluid type with a non-nutritive sweetener may have an impact on thirst; it is unclear how age may impact this. As such, it is hypothesised that fluid consumption of both water and the non-nutritive sweetened beverage will be different between age groups. The study uses a randomised crossover design; participants will serve as their own control as they complete both experimental sessions.

Trial website

Trial related presentations / publications

Public notes

Contacts

Principal investigator

Name

Prof Ollie Jay

Address

Susan Wakil Health Building (D18), The University of Sydney, Western Avenue, Camperdown, NSW 2006, Australia

Country

Australia

Phone

+61 449116760

Fax

[email protected]

Contact person for public queries

Name

Jake McCahon

Address

Susan Wakil Health Building (D18), The University of Sydney, Western Avenue, Camperdown, NSW 2006, Australia

Country

Australia

Phone

+61 451311579

Fax

[email protected]

Contact person for scientific queries

Name

Jake McCahon

Address

Susan Wakil Health Building (D18), The University of Sydney, Western Avenue, Camperdown, NSW 2006, Australia

Country

Australia

Phone

+61 451311579

Fax

[email protected]

Data sharing statement

Will the study consider sharing individual participant data?

Yes

Will there be any conditions when requesting access to individual participant data?

Persons/groups eligible to request access:
• Researchers
Conditions for requesting access:
• Yes, conditions apply:
• Requires review on a case-by-case basis by the trial custodian, sponsor or data sharing committee
• Requires a scientifically sound proposal or protocol
• Requires approval by an ethics committee
• Requires a data sharing agreement between data requester and trial custodian or sponsor

What individual participant data might be shared?

• De-identified individual participant data:
• All outcomes data
• Published results
• Primary outcome(s)

What types of analyses could be done with individual participant data?

• Any type of analysis (i.e. no restrictions on data re-use)
• Systematic reviews and meta-analyses

When can requests for individual participant data be made (start and end dates)?

From:
After publication of main results
To:
Not yet decided

Where can requests to access individual participant data be made, or data be obtained directly?

• Email of trial custodian, sponsor or committee: Can be obtained by contacting a member of the publishing team.
Email address (s) to use is the following:
- [email protected] (Researcher performing data collection, analysis, writing)
- [email protected] (PI)

Are there extra considerations when requesting access to individual participant data?

What supporting documents are/will be available?

No Supporting Document Provided

Results publications and other study-related documents

Documents added manually

No documents have been uploaded by study researchers.

Documents added automatically

No additional documents have been identified.

Trial Review

Documents added manually

Documents added automatically