The Effects of Increased Water Intake on Muscle Function, Physical Performance, and Endocrine Regulation in Low-Drinking Older Adults (HydraAge)

November 5, 2026 updated by: Rúben Francisco, Polytechnic University of Santarém

The Effects of Increased Water Intake on Muscle Function, Physical Performance, and Endocrine Regulation in Low-Drinking Older Adults: A Randomized Controlled Trial

Population aging represents one of the major demographic transformations of the 21st century. However, increased longevity has not been accompanied by preserved functional independence. Falls are currently the leading cause of injury-related mortality and a major contributor to hospitalization, disability, and institutionalization among older adults. Even subtle deficits in muscle strength, balance, and mobility can significantly increase fall risk, triggering a cycle of functional decline and frailty.

Emerging evidence suggests that hydration status may represent a modifiable determinant of neuromuscular function. Many older adults live in a state of chronically low water intake, a condition associated with subtle yet persistent alterations in endocrine regulation and body water distribution. Total body water is distributed between extracellular and intracellular compartments, the latter being particularly relevant to muscle quality. Observational studies demonstrate that higher intracellular water levels are associated with greater strength, faster gait speed, better overall functional performance, and lower fall risk. In parallel, low water intake is associated with elevated arginine vasopressin (AVP) concentrations, a hormone with systemic effects that may contribute to metabolic stress and potential impairment of muscle function.

Despite water being the most accessible and low-cost health intervention, no randomized controlled trials have examined whether increasing daily water intake can improve fall-related functional performance in older adults with habitual low intake.

The HYDRAGE study aims to address this gap through a randomized controlled trial evaluating the effects of increasing daily water intake in adults aged ≥50 years with habitual intake ≤35 ml/kg/day. Participants will be allocated to either a control group (maintaining habitual intake) or an experimental group (≥45 ml/kg/day) for 7 days. The primary objective is to assess the effect of increased water intake on neuromuscular strength, specifically isokinetic knee extension and handgrip strength, as key determinants of fall risk. Secondary objectives include evaluating fall-related functional performance (SPPB and TUG), endocrine regulation (AVP), hydration biomarkers (urine and saliva osmolality and urine specific gravity, assessed using an osmometer), body water distribution (ECW/ICW ratio and phase angle, assessed by bioelectrical impedance analysis), physical activity levels, and psychological state.

We hypothesize that increasing daily water intake will improve fall-related functional performance, with these effects being partially explained by improvements in intracellular hydration and reductions in AVP-mediated endocrine stress.

By prioritizing clinically meaningful functional outcomes while integrating underlying physiological mechanisms, the project combines translational relevance with mechanistic depth. Because both the intervention and the functional assessments are simple, low-cost, and easily deployable across clinical and community settings, the study presents strong scalability potential as a strategy for fall prevention and healthy aging.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Detailed Description

Population aging is one of the most significant public health transformations of the 21st century [1]. However, increased longevity has not been accompanied by preserved independence. Falls have emerged as the leading cause of injury-related mortality and a major driver of hospitalization, disability, and institutionalization among older adults [2]. A recent national study [3] revealed that 34.9% of all fall incidents occurred in individuals aged 85 and older. Additionally, the incidence of falls among adults aged 50-60 years was 19%, increasing to 28% in those aged 70 and above [3]. Beyond the immediate trauma, falls often initiate a cascade of functional decline, fear of movement, reduced physical activity, and progressive frailty [4]. At the core of fall susceptibility lies the age-related decline in neuromuscular function, balance control, and lower-limb strength, i.e., biological hallmarks of aging that compromise functional autonomy [5]. In particular, lower-limb muscle strength and power and handgrip strength decline progressively with age and have consistently been associated with increased fall risk [6, 7]. Lower-limb strength is essential to support body weight, maintain postural stability, and recover from perturbations, whereas handgrip strength may function as a protective "second line of defense," enabling older adults to grasp support surfaces and attenuate the impact of a fall. The low levels of physical activity exacerbate the decline typically observed in older adults, further diminishing muscle function and functional independence [5]. Emerging evidence, however, highlights hydration as an overlooked determinant of functionality and muscle performance in the elderly [8]. Paradoxically, despite tightly regulated homeostatic mechanisms, many individuals live in a state of chronic low water intake (LWI) [9]. Older adults are uniquely predisposed to this state due to impaired thirst perception [10], renal changes [11], polypharmacy [12], and mobility restrictions [12]. Importantly, even subtle impairments in neuromuscular function or balance may substantially increase fall risk in this population. Additionally, total body water (TBW) is divided into extracellular water (ECW) and intracellular water (ICW), with ICW being closely tied to muscle quality: older adults with higher ICW, even when lean mass is comparable, exhibit superior strength, functionality, gait speed, and a lower risk of falls [13, 14].

These findings suggest that water distribution is not merely a reflection of health status but a modifiable determinant of neuromuscular integrity and fall susceptibility [13, 14]. Yet, despite water being the most accessible, low-cost, and universally available health intervention, randomized trials examining whether increasing daily water intake can improve functional performance, reduce fall risk, and improve body water distribution in older adults are virtually nonexistent [15]. Beyond structural hydration compartments, endocrine regulation represents an additional pathway linking LWI to functional decline. The state of underhydration is characterized by persistently elevated arginine vasopressin (AVP) concentrations [9]. Although this state maintains TBW and plasma osmolality within narrow ranges [9], it may do so at a physiological cost.

Chronic AVP elevation has been associated with conditions such as kidney stones [16], insulin resistance [16], inflammation [17], mood changes [18], and skeletal muscle atrophy [18], all of which are closely linked to chronic diseases [16]. Specifically, AVP plays a central role in this discussion. Beyond its antidiuretic function, elevated circulating AVP has been shown to promote hyperglycemia, stimulate hepatic gluconeogenesis, and increase plasma glucagon concentration [19]. Individuals with type 2 diabetes consistently exhibit higher plasma AVP concentrations, supporting a plausible mechanistic link between chronic LWI and metabolic dysregulation [19]. In addition, activation of the renin angiotensin-aldosterone system in response to LWI or sustained water loss can impair insulin signaling via elevated aldosterone concentrations [20], while chronic alterations in cellular hydration status may directly affect cellular metabolism in ways that favor insulin resistance [21].

Furthermore, LWI may indirectly influence metabolic health by modulating dietary glycemic load, as water consumption with meals can attenuate postprandial glycemic responses [22]. Thus, it must be concluded that beyond musculoskeletal function, chronic LWI has been consistently associated with systemic metabolic disturbances that may further accelerate functional decline. To date, no trial has examined whether improving hydration could preserve muscle strength and power, improve the balance of water distribution across compartments, enhance physical activity levels, or improve the pathological elevation of AVP in older adults. The HYDRAGE study was therefore designed to address this critical gap.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
78

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Contact Backup

Study Locations

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

50 years to 85 years (Adult, Older Adult)

Accepts Healthy Volunteers

Yes

Genders Eligible for Study

All

Description

Inclusion Criteria:

  1. Age ≥50 years.
  2. Habitual low water intake (≤35 ml/kg/day), confirmed through dietary assessment.
  3. Community-dwelling and able to attend study visits at the SPRINT laboratories.
  4. Independent ambulation (without an assistive device).
  5. Stable clinical condition for at least three months before enrollment.
  6. Auto reported adequate cognitive function to provide informed consent and comply with study procedures.
  7. Willingness to maintain habitual physical activity and dietary patterns (except for prescribed water intake modification)

Exclusion Criteria:

  1. Clinically unstable cardiovascular disease.

  2. Clinically unstable renal disease.

  3. Clinically unstable metabolic or endocrine disease.

  4. Clinically unstable type 2 diabetes.

  5. Any medical condition requiring fluid restriction.

  6. Known history of recurrent hyponatremia.

  7. Chronic use of medications known to substantially affect fluid and electrolyte balance, including:- Loop diuretics;

    • Thiazide diuretics;
    • Desmopressin;
    • Sodium-glucose cotransporter-2 (SGLT2) inhibitors.

  8. Cognitive impairment preventing the provision of informed consent.

  9. Musculoskeletal or neurological conditions that preclude participation in physical performance assessments.

  10. Major surgery within the previous six months.

  11. Current alcohol or substance abuse.

  12. Participation in another clinical trial within the previous three months.

  13. Any other condition considered by the investigators to compromise participant safety, study compliance, or interpretation of the study results.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Basic Science
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Single

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: Increased Water Intake

Participants will maintain their habitual total water intake and usual dietary and physical activity patterns throughout the 7-day study period. Participants will not receive the hydration tools or behavioral support provided to the experimental group.
Other: Water

Participants will be assigned at random to either the experimental group (EG) or the control group (CG). Over the 7-day intervention period, the EG will be asked to increase total daily water intake (WI) to at least 45 mL·kg-¹·day-¹, while the CG will continue their usual water consumption, corresponding to ≤35 mL·kg-¹·day-¹. Total WI will account for water obtained from both beverages and food.

Participants allocated to the EG will be instructed to keep their usual dietary habits unchanged during the intervention so that the amount of water derived from food remains comparable to habitual intake. Accordingly, the intervention will involve an increase in fluid consumption only. The additional amount of water required to reach the target of ≥45 mL·kg-¹·day-¹ will be individually determined based on body mass and the estimated contribution of food to total WI. Vimeiro Original natural mineral water will be used as the additional source of fluid.
No Intervention: No intervention

Participants will maintain their habitual total water intake and usual dietary and physical activity patterns throughout the 7-day study period. No additional water, hydration tools, or behavioral support will be provided. Participants will complete daily food and fluid records to document their habitual intake during the intervention period.

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Absolute and Relative Ankle Plantar-Flexion Peak Force
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

Absolute peak force (N) and relative peak force (N·kg-¹) during a seated maximal voluntary isometric plantar-flexion contraction of the dominant limb. The highest force value recorded across four trials will be used for analysis.
Day 1 (baseline) and Day 7 (post-intervention)
Rate of Force Development During Isometric Ankle Plantar-Flexion
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

Rate of force development (RFD; N·s-¹) during maximal voluntary isometric plantar-flexion of the dominant limb, calculated over consecutive 50-ms intervals from contraction onset: 0-50, 50-100, 100-150, and 150-200 ms.
Day 1 (baseline) and Day 7 (post-intervention)
Rate of Force Development During Dynamic Ankle Plantar-Flexion
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

Rate of force development (N·s-¹) during a standing bilateral rapid calf-raise task, calculated as peak force (N) divided by time to peak force (s).
Day 1 (baseline) and Day 7 (post-intervention)
Explosive Isometric Ankle Plantar-Flexion Force
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

Explosive force, expressed as the percentage of peak force (%F) attained at 50, 100, 150, and 200 ms following contraction onset during maximal voluntary isometric plantar-flexion of the dominant limb.
Day 1 (baseline) and Day 7 (post-intervention)
Peak Force during the 5 repetition STS
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

Peak vertical ground reaction force (N) recorded during the concentric phase of each sit-to-stand repetition. The participant-level summary measure will be defined a priori.
Day 1 (baseline) and Day 7 (post-intervention)
Fatigue Index During the 30-Second Sit-to-Stand Test
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

Fatigue index calculated to quantify the decline in performance across successive sit-to-stand repetitions during the 30-s STS. The calculation method will be specified a priori.
Day 1 (baseline) and Day 7 (post-intervention)
Mean Power During the 30-Second Sit-to-Stand Test
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

Mean lower-limb muscle power during the 30-s STS, estimated using a previously validated equation.
Day 1 (baseline) and Day 7 (post-intervention)

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Time to Complete the First Five Sit-to-Stand Repetitions
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

Time (s) required to complete the first five sit-to-stand repetitions during the 30-s STS test, measured from the onset of the first repetition until completion of the fifth repetition. Only participants completing at least five repetitions will be included in this analysis.
Day 1 (baseline) and Day 7 (post-intervention)
Functional Lower-Limb Performance
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

Number of completed repetitions during the 30-second sit-to-stand test (30-s STS), performed from a 43-cm armless chair.
Day 1 (baseline) and Day 7 (post-intervention)
Change in Handgrip strength
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

Handgrip strength will be assessed using a portable hand dynamometer (Jamar Plus+). Participants will perform three maximal voluntary isometric contractions with each hand alternately. A 60-second rest period will be provided between attempts. The highest recorded value will be used for analysis. The outcome will be expressed as the change in handgrip strength from baseline to the post-intervention assessment.
Day 1 (baseline) and Day 7 (post-intervention)
Change in Short Physical Performance Battery Score
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

Functional performance will be assessed using the Short Physical Performance Battery (SPPB), comprising static balance, 4-meter gait speed, and repeated chair stand tests. The SPPB score will be calculated according to the standardized scoring procedure. The outcome will be expressed as the change in SPPB score from baseline to the post-intervention assessment.
Day 1 (baseline) and Day 7 (post-intervention)
Change in Timed Up and Go Test Performance
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

The Timed Up and Go (TUG) test will assess functional mobility and fall risk. Participants will stand from a chair, walk 3 meters, turn around a reference point, return to the chair, and sit down. The time required to complete the test will be recorded. The outcome will be expressed as the change in TUG completion time from baseline to the post-intervention assessment.
Day 1 (baseline) and Day 7 (post-intervention)
Change in Serum Arginine Vasopressin Concentration
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

Serum arginine vasopressin (AVP), will be assessed as a biomarker of the physiological regulation of water balance. Venous blood samples will be collected in the morning after an overnight fast. Serum AVP concentration will be determined using a radioimmunoassay (RIA) according to the standardized procedures of the clinical laboratory. The outcome will be expressed as the change in serum AVP concentration from baseline to the post-intervention assessment.
Day 1 (baseline) and Day 7 (post-intervention)
Change in Fasting Serum Glucose Concentration
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

Fasting serum glucose concentration will be assessed as a biochemical marker of glucose metabolism. Venous blood samples will be collected in the morning following an overnight fast of 8-12 hours. Serum glucose concentration will be determined using the hexokinase-glucose-6-phosphate dehydrogenase enzymatic method according to the standardized procedures of the clinical laboratory. The outcome will be expressed as the change in fasting serum glucose concentration from baseline to the post-intervention assessment.
Day 1 (baseline) and Day 7 (post-intervention)
Change in Serum Cortisol Concentration
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

Serum basal cortisol concentration will be assessed as an endocrine biomarker. Venous blood samples will be collected in the morning following an overnight fast, with the time of blood collection recorded to account for the circadian variation in cortisol concentrations. Serum cortisol concentration will be determined using a chemiluminescence assay according to the standardized procedures of the clinical laboratory. The outcome will be expressed as the change in serum cortisol concentration from baseline to the post-intervention assessment.
Day 1 (baseline) and Day 7 (post-intervention)
Change in Fasting Serum Insulin Concentration
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

Fasting serum insulin concentration will be assessed as a biochemical marker of insulin metabolism. Venous blood samples will be collected in the morning following an overnight fast of 8-12 hours. Serum insulin concentration will be determined using a chemiluminescence immunoassay according to the standardized procedures of the clinical laboratory. The outcome will be expressed as the change in fasting serum insulin concentration from baseline to the post-intervention assessment.
Day 1 (baseline) and Day 7 (post-intervention)
Change in Homeostatic Model Assessment of Insulin Resistance (HOMA-IR)
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

Insulin resistance will be estimated using the Homeostatic Model Assessment of Insulin Resistance (HOMA-IR), calculated from fasting serum glucose and fasting serum insulin concentrations. HOMA-IR will be calculated as: fasting insulin (μU/mL) × fasting glucose (mmol/L) / 22.5. The outcome will be expressed as the change in HOMA-IR from baseline to the post-intervention assessment.
Day 1 (baseline) and Day 7 (post-intervention)
Change in serum osmolality
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

Serum, osmolality (mOsm/kg) will be measured using a freezing-point depression osmometer (Mod OSMO1, Advanced Instruments, Canada). All osmolality measurements will be performed in duplicate.
Day 1 (baseline) and Day 7 (post-intervention)
Change in saliva osmolality
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

Saliva osmolality (mOsm/kg) will be measured using a freezing-point depression osmometer (Mod OSMO1, Advanced Instruments, Canada). All osmolality measurements will be performed in duplicate. Unstimulated saliva samples will be collected with participants seated comfortably after resting quietly for 2 min, allowing saliva to accumulate passively in the mouth. Participants will then provide approximately 3-4 mL of saliva into Salivette collection tubes or until no additional saliva can be comfortably produced.
Day 1 (baseline) and Day 7 (post-intervention)
Change in urine osmolality
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

Urine osmolality (mOsm/kg) will be measured using a freezing-point depression osmometer (Mod OSMO1, Advanced Instruments, Canada). Urine samples will be collected in sterile urine collection cups at the specified assessment time point. Participants will be instructed to provide a midstream urine sample after discarding the initial urine stream. All osmolality measurements will be performed in duplicate.
Day 1 (baseline) and Day 7 (post-intervention)
Change in Urine Specific Gravity
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

Urine specific gravity (USG) will be assessed as a urinary marker of hydration status. A urine sample will be collected at the specified assessment time point, and USG will be determined using a digital refractometer (KERN ORM 1CO, KERN & Sohn GmbH, Germany). The outcome will be expressed as the change in urine specific gravity from baseline to the post-intervention assessment.
Day 1 (baseline) and Day 7 (post-intervention)
Change in Urine Color
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

Urine color will be assessed as a subjective urinary marker of hydration status. Urine color will be evaluated from a urine sample collected at the specified assessment time point using a standardized urine color scale. The outcome will be expressed as the change in urine color from baseline to the post-intervention assessment.
Day 1 (baseline) and Day 7 (post-intervention)
Change in Total Water Intake
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

Total water intake (WI), including water obtained from beverages and foods, will be assessed using three-day food diaries. A certified dietitian will provide standardized instructions regarding portion sizes and food and beverage recording. Food Processor Plus® software will be used to estimate daily total water intake. The outcome will be expressed as the change in average daily total water intake from the screening/baseline assessment to the intervention period.
Day 1 (baseline) and Day 7 (post-intervention)
Change in Body Mass Index
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

Body mass index (BMI) will be calculated as body mass in kilograms divided by height in meters squared (kg/m²). Body mass and height will be assessed under standardized conditions. The outcome will be expressed as the change in BMI from baseline to the post-intervention assessment.
Day 1 (baseline) and Day 7 (post-intervention)
Change in Total Body Water
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

Total body water (TBW) will be estimated using whole-body and segmental bioelectrical impedance analysis (BIA) using a phase-sensitive single-frequency analyzer (AKERN BIA 101/BIVA PRO; Akern Srl, Florence, Italy). Participants will rest in the supine position for 10 minutes before assessment. The outcome will be expressed as the change in estimated total body water from baseline to the post-intervention assessment.
Day 1 (baseline) and Day 7 (post-intervention)
Change in Intracellular Water
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

Intracellular water (ICW) will be estimated using whole-body and segmental bioelectrical impedance analysis. The outcome will be expressed as the change in estimated intracellular water from baseline to the post-intervention assessment.
Day 1 (baseline) and Day 7 (post-intervention)
Change in Extracellular Water
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

Extracellular water (ECW) will be estimated using whole-body and segmental bioelectrical impedance analysis. The outcome will be expressed as the change in estimated extracellular water from baseline to the post-intervention assessment.
Day 1 (baseline) and Day 7 (post-intervention)
Change in Extracellular-to-Intracellular Water Ratio
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

The extracellular-to-intracellular water ratio (ECW/ICW) will be calculated from bioelectrical impedance-derived estimates of extracellular and intracellular water. The outcome will be expressed as the change in the ECW/ICW ratio from baseline to the post-intervention assessment.
Day 1 (baseline) and Day 7 (post-intervention)
Change in Bioelectrical Impedance Phase Angle
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

Whole-body and segmental phase angle (PhA) will be obtained from resistance and reactance measurements using a phase-sensitive single-frequency bioelectrical impedance analyzer. The outcome will be expressed as the change in phase angle from baseline to the post-intervention assessment.
Day 1 (baseline) and Day 7 (post-intervention)
Change in Resistance-to-Height Ratio
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

The resistance-to-height ratio (R/H) will be calculated from raw bioelectrical impedance resistance measurements normalized for participant height. The outcome will be expressed as the change in R/H from baseline to the post-intervention assessment.
Day 1 (baseline) and Day 7 (post-intervention)
Change in Reactance-to-Height Ratio
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

The reactance-to-height ratio (Xc/H) will be calculated from raw bioelectrical impedance reactance measurements normalized for participant height. The outcome will be expressed as the change in Xc/H from baseline to the post-intervention assessment.
Day 1 (baseline) and Day 7 (post-intervention)
Change in Impedance-to-Height Ratio
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

The Impedance-to-height ratio (Z/H) will be calculated from raw bioelectrical impedance reactance measurements normalized for participant height. The outcome will be expressed as the change in Z/H from baseline to the post-intervention assessment.
Day 1 (baseline) and Day 7 (post-intervention)
Change in Perceived Thirst
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

Perceived thirst will be assessed using a 10-cm visual analogue scale (VAS). Participants will indicate their subjective level of thirst by placing a mark along the scale according to their perceived sensation. The outcome will be expressed as the change in thirst VAS score from baseline to the post-intervention assessment.
Day 1 (baseline) and Day 7 (post-intervention)
Change in Profile of Mood States Score
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

Psychological state will be assessed using the Profile of Mood States (POMS), a 65-item self-administered questionnaire assessing six mood dimensions: tension-anxiety, depression-dejection, anger-hostility, fatigue-inertia, vigor-activity, and confusion-bewilderment. The outcome will be expressed as the change in POMS scores from baseline to the post-intervention assessment.
Day 1 (baseline) and Day 7 (post-intervention)
Change in Health-Related Quality of Life
Time Frame: Day 1 (baseline) and Day 7 (post-intervention)

Health-related quality of life will be assessed using the 36-Item Short Form Health Survey (SF-36). The questionnaire assesses eight domains of physical and mental health and provides physical and mental component summary scores. The outcome will be expressed as the change in SF-36 scores from baseline to the post-intervention assessment.
Day 1 (baseline) and Day 7 (post-intervention)

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Polytechnic University of Santarém

Collaborators

Collaborators

An organization other than the sponsor that provides support for a clinical study. This support may include activities related to funding, design, implementation, data analysis, or reporting.
National Health Institute Dr. Ricardo Jorge

Investigators

Investigators

A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator.
  • Principal Investigator: Rúben Francisco Francisco, PhD, Sport Physical Activity and Health Research & Innovation Center

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
January 1, 2027

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
April 30, 2027

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
July 31, 2028

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
October 18, 2026

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
October 18, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
October 23, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
November 12, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
November 5, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
November 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • HydrAge - SPRINT
  • 2025 (U.S. NIH Grant/Contract)
  • 2025.17619.PTDC (Other Grant/Funding Number: Fundação para a Ciência e Tecnologia)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

Individual participant data will not be made publicly available because of participant privacy and data protection considerations. The study data will be handled confidentially and access to identifiable information will be restricted to authorized members of the research team. De-identified data may be made available upon reasonable request, subject to approval by the research team, applicable ethical requirements, and institutional and data protection regulations.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

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