Water-Inertia-Based Dynamic Stability Training for Balance and Postural Control in Healthy Young Women

September 4, 2026 updated by: Yuanyan Huang

Effects of Water-Inertia-Based Dynamic Stability Training on Dynamic Balance and Single-Leg Postural Control in Healthy Young Women: A Randomized Controlled Trial

This randomized controlled study evaluated the effects of a 10-week dynamic stability training program using a mobile water load compared with a mass-matched stable load in healthy young women. Thirty participants were randomly assigned to either water-inertia-based unstable-load training or stable-load training. Both groups completed the same supervised exercises three times per week, using vests with the same total external mass; the main difference between groups was whether the load inside the vest was mobile or stable. Outcomes were assessed before training, after 5 weeks, and after 10 weeks. The study evaluated dynamic balance, postural sway during single-leg stance, and other physical-performance outcomes to determine whether mobile water loading produced different training adaptations from stable loading.

Study Overview

Status

Status

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

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

This study was designed to examine whether dynamic stability training performed with a mobile water-based external load produces different physical and postural adaptations from the same training performed with a mass-matched stable external load in healthy young women. The study used a randomized, parallel-group design.

Healthy female university students aged 19-25 years who had not participated in resistance training during the previous 12 months were recruited. After baseline assessment, 30 eligible participants were randomly assigned in a 1:1 ratio to an unstable-load training group or a stable-load training group.

Both groups completed the same supervised dynamic stability training program three times per week for 10 weeks, for a total of 30 training sessions. Each session lasted approximately 50 minutes. The exercise content, training frequency, session duration, set-repetition structure, rest intervals, vest mass, and any additional prescribed exercise loads were matched between groups. During the main training block, participants completed three sets of each exercise, with 12 repetitions per set during weeks 1-5 and 15 repetitions per set during weeks 6-10.

The unstable-load group trained while wearing an Aqua Vest containing a total external load of 5 kg, consisting of approximately 4 kg of water and a 1-kg vest. Because the water pouches were partially filled, the internal water could move during exercise and change the distribution of the external load. The stable-load group wore a mass-matched weighted vest containing approximately 4 kg of steel rods and a 1-kg vest. The steel rods were arranged to approximate the spatial distribution of the water pouches. Thus, the primary experimental difference between groups was the mobility of the external load rather than total vest mass or prescribed exercise content.

Assessments were conducted at baseline, after 5 weeks of training, and after 10 weeks of training. Dynamic postural control was evaluated using the Y-Balance Test. Participants completed reaching tasks in the anterior, posteromedial, and posterolateral directions while standing on one limb. The maximum valid reach distance in each direction was retained and normalized to limb length, and a composite score was also calculated.

Postural sway was evaluated during single-leg stance using force-platform-derived center-of-pressure measures under eyes-open and eyes-closed conditions. Eyes-open trials lasted 30 seconds and eyes-closed trials lasted 20 seconds. Center-of-pressure outcomes included total path distance and direction-specific root-mean-square displacement in the anteroposterior and mediolateral directions.

The broader study protocol also included lower-extremity physical-performance assessments. The registration record is intended to describe the original study protocol and design; individual publications arising from the study may focus on specific subsets of the collected outcomes.

The purpose of the comparison was to determine whether introducing load mobility through a water-filled vest, while keeping the prescribed exercise program and external mass closely matched, resulted in different adaptations from training with a stable weighted vest.

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 (Actual)

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.
30

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 Locations

  • South Korea
      • Busan, South Korea
        • Busan University of Foreign Studies

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

  • Adult

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria:

  • Female undergraduate students aged 19 to 25 years.
  • Generally healthy at the time of enrollment.
  • No surgery within the previous 6 months.
  • No congenital, neurological, vestibular, or musculoskeletal disorder affecting the foot, pelvis, or spine.
  • No participation in resistance training during the previous 12 months. Able and willing to participate in the 10-week supervised exercise intervention and study assessments.
  • Provided written informed consent to participate.

Exclusion Criteria:

  • Did not meet any of the inclusion criteria.
  • Participated in resistance training or functional training outside the study intervention during the 10-week study period.
  • Developed a health condition, injury, or other circumstance during the study that prevented safe participation in the prescribed exercise program or outcome assessments.

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: Other
  • 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: Water-Inertia-Based Unstable-Load Training
Participants assigned to this arm completed a supervised 10-week dynamic stability training program three times per week while wearing an Aqua Vest with a total external load of 5 kg, consisting of approximately 4 kg of water and a 1-kg vest. The partially filled water pouches allowed internal water movement during exercise, creating a mobile external load. Exercise content, session duration, set-repetition structure, rest intervals, and any additional prescribed exercise loads were matched to the stable-load training arm.
Behavioral: Water-Inertia-Based Dynamic Stability Training
Participants completed a supervised dynamic stability training program three times per week for 10 weeks (30 sessions), with each session lasting approximately 50 minutes. During training, participants wore a vest providing a total external load of 5 kg, consisting of approximately 4 kg of water in partially filled pouches and a 1-kg vest. Internal water movement allowed the external load distribution to change during exercise. Exercises were performed for three sets, with 12 repetitions per set during weeks 1-5 and 15 repetitions per set during weeks 6-10, with 30 seconds of rest between sets. Exercise content and any additional prescribed implement loads were matched to the stable-load intervention.
Other Names:
  • Unstable-Load Training (ULT)
  • Aqua Vest Training
Active Comparator: Stable-Load Training
Participants assigned to this arm completed the same supervised 10-week dynamic stability training program three times per week while wearing a mass-matched stable weighted vest with a total external load of 5 kg, consisting of approximately 4 kg of steel rods and a 1-kg vest. The steel rods were arranged to approximate the spatial loading configuration of the water pouches. Exercise content, session duration, set-repetition structure, rest intervals, and any additional prescribed exercise loads were matched to the unstable-load training arm.
Behavioral: Stable-Load Dynamic Stability Training
Participants completed the same supervised dynamic stability training program three times per week for 10 weeks (30 sessions), with each session lasting approximately 50 minutes. During training, participants wore a stable weighted vest providing a total external load of 5 kg, consisting of approximately 4 kg of steel rods and a 1-kg vest. The steel rods were arranged to approximate the spatial loading configuration of the water pouches used in the water-inertia intervention. Exercises were performed for three sets, with 12 repetitions per set during weeks 1-5 and 15 repetitions per set during weeks 6-10, with 30 seconds of rest between sets. Exercise content and any additional prescribed implement loads were matched between groups.
Other Names:
  • Stable-Load Training (SLT)
  • Weighted Vest Training

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
Normalized Anterior Reach Distance on the Y-Balance Test
Time Frame: Baseline, Week 5, and Week 10
Dynamic postural control was assessed using the lower-quarter Y-Balance Test. Participants performed three valid anterior reach trials while maintaining single-leg stance. The maximum reach distance was retained and normalized to the corresponding limb length: normalized reach distance (%) = maximum reach distance / limb length × 100. Higher values indicate greater normalized reach performance.
Baseline, Week 5, and Week 10
Normalized Posteromedial Reach Distance on the Y-Balance Test
Time Frame: Baseline, Week 5, and Week 10
Participants performed three valid posteromedial reach trials during the lower-quarter Y-Balance Test. The maximum reach distance was retained and normalized to the corresponding limb length: normalized reach distance (%) = maximum reach distance / limb length × 100. Higher values indicate greater normalized reach performance.
Baseline, Week 5, and Week 10
Normalized Posterolateral Reach Distance on the Y-Balance Test
Time Frame: Baseline, Week 5, and Week 10
Participants performed three valid posterolateral reach trials during the lower-quarter Y-Balance Test. The maximum reach distance was retained and normalized to the corresponding limb length: normalized reach distance (%) = maximum reach distance / limb length × 100. Higher values indicate greater normalized reach performance.
Baseline, Week 5, and Week 10
Y-Balance Test Composite Score
Time Frame: Baseline, Week 5, and Week 10
The composite score was calculated from the maximum valid anterior, posteromedial, and posterolateral reach distances normalized to limb length: composite score (%) = (maximum anterior + maximum posteromedial + maximum posterolateral reach distance) / (3 × limb length) × 100. Higher values indicate greater overall Y-Balance Test performance.
Baseline, Week 5, and Week 10
Center-of-Pressure Total Distance During Eyes-Open Single-Leg Stance
Time Frame: Baseline, Week 5, and Week 10
Postural sway was assessed using a force platform during 30-second eyes-open single-leg stance. Total CoP distance (cm) represented the cumulative path length of the center-of-pressure trajectory during each valid trial. Three trial-specific values were averaged for analysis. Lower values represent a shorter CoP trajectory during the test condition.
Baseline, Week 5, and Week 10
Anteroposterior CoP RMS During Eyes-Open Single-Leg Stance
Time Frame: Baseline, Week 5, and Week 10
Anteroposterior root-mean-square (AP RMS) displacement of the center of pressure was calculated during 30-second eyes-open single-leg stance and expressed in centimeters. AP RMS represents the dispersion of CoP displacement about its mean position in the anteroposterior direction. Three trial-specific values were averaged for analysis.
Baseline, Week 5, and Week 10
Mediolateral CoP RMS During Eyes-Open Single-Leg Stance
Time Frame: Baseline, Week 5, and Week 10
Mediolateral root-mean-square (ML RMS) displacement of the center of pressure was calculated during 30-second eyes-open single-leg stance and expressed in centimeters. ML RMS represents the dispersion of CoP displacement about its mean position in the mediolateral direction. Three trial-specific values were averaged for analysis.
Baseline, Week 5, and Week 10
Center-of-Pressure Total Distance During Eyes-Closed Single-Leg Stance
Time Frame: Baseline, Week 5, and Week 10
Postural sway was assessed using a force platform during 20-second eyes-closed single-leg stance. Total CoP distance (cm) represented the cumulative path length of the center-of-pressure trajectory during each valid trial. Three trial-specific values were averaged for analysis. Lower values represent a shorter CoP trajectory during the test condition.
Baseline, Week 5, and Week 10
Anteroposterior CoP RMS During Eyes-Closed Single-Leg Stance
Time Frame: Baseline, Week 5, and Week 10
Anteroposterior root-mean-square (AP RMS) displacement of the center of pressure was calculated during 20-second eyes-closed single-leg stance and expressed in centimeters. AP RMS represents the dispersion of CoP displacement about its mean position in the anteroposterior direction. Three trial-specific values were averaged for analysis.
Baseline, Week 5, and Week 10
Mediolateral CoP RMS During Eyes-Closed Single-Leg Stance
Time Frame: Baseline, Week 5, and Week 10
Mediolateral root-mean-square (ML RMS) displacement of the center of pressure was calculated during 20-second eyes-closed single-leg stance and expressed in centimeters. ML RMS represents the dispersion of CoP displacement about its mean position in the mediolateral direction. Three trial-specific values were averaged for analysis.
Baseline, Week 5, and Week 10
Knee Extension Peak Torque Relative to Body Weight at 60°/s
Time Frame: Baseline, Week 5, and Week 10
Concentric knee extension strength was assessed using an isokinetic dynamometer at an angular velocity of 60°/s. Peak torque was normalized to body weight and expressed as a percentage of body weight (PT/BW, %). Higher values indicate greater knee extensor torque relative to body weight.
Baseline, Week 5, and Week 10
Knee Flexion Peak Torque Relative to Body Weight at 60°/s
Time Frame: Baseline, Week 5, and Week 10
Concentric knee flexion strength was assessed using an isokinetic dynamometer at an angular velocity of 60°/s. Peak torque was normalized to body weight and expressed as a percentage of body weight (PT/BW, %). Higher values indicate greater knee flexor torque relative to body weight.
Baseline, Week 5, and Week 10
Ankle Inversion Peak Torque Relative to Body Weight at 60°/s
Time Frame: Baseline, Week 5, and Week 10
Concentric ankle inversion strength was assessed using an isokinetic dynamometer at an angular velocity of 60°/s. Peak torque was normalized to body weight and expressed as a percentage of body weight (PT/BW, %). Higher values indicate greater inversion torque relative to body weight.
Baseline, Week 5, and Week 10
Ankle Eversion Peak Torque Relative to Body Weight at 60°/s
Time Frame: Baseline, Week 5, and Week 10
Concentric ankle eversion strength was assessed using an isokinetic dynamometer at an angular velocity of 60°/s. Peak torque was normalized to body weight and expressed as a percentage of body weight (PT/BW, %). Higher values indicate greater eversion torque relative to body weight.
Baseline, Week 5, and Week 10
Ankle Inversion Peak Torque Relative to Body Weight at 120°/s
Time Frame: Baseline, Week 5, and Week 10
Concentric ankle inversion strength was assessed using an isokinetic dynamometer at an angular velocity of 120°/s. Peak torque was normalized to body weight and expressed as a percentage of body weight (PT/BW, %). Higher values indicate greater inversion torque relative to body weight.
Baseline, Week 5, and Week 10
Ankle Eversion Peak Torque Relative to Body Weight at 120°/s
Time Frame: Baseline, Week 5, and Week 10
Concentric ankle eversion strength was assessed using an isokinetic dynamometer at an angular velocity of 120°/s. Peak torque was normalized to body weight and expressed as a percentage of body weight (PT/BW, %). Higher values indicate greater eversion torque relative to body weight.
Baseline, Week 5, and Week 10

Other Outcome Measures

Other Outcome Measures

For clinical trials, a planned measurement described in the protocol that is used to determine the effect of an intervention/treatment on participants. For observational studies, a measurement or observation that is used to describe patterns of diseases or traits, or associations with exposures, risk factors, or treatment. Types of outcome measures include primary outcome measure and secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Knee Extension Test Range of Motion at 60°/s
Time Frame: Baseline, Week 5, and Week 10
Range of motion recorded by the isokinetic dynamometer during the knee extension test performed at 60°/s, expressed in degrees. This measure represents the angular range recorded during the corresponding isokinetic testing condition.
Baseline, Week 5, and Week 10
Knee Flexion Test Range of Motion at 60°/s
Time Frame: Baseline, Week 5, and Week 10
Range of motion recorded by the isokinetic dynamometer during the knee flexion test performed at 60°/s, expressed in degrees.
Baseline, Week 5, and Week 10
Ankle Inversion Test Range of Motion at 60°/s
Time Frame: Baseline, Week 5, and Week 10
Range of motion recorded by the isokinetic dynamometer during the inversion test performed at 60°/s, expressed in degrees. This measure represents the angular range recorded during the corresponding isokinetic testing condition.
Baseline, Week 5, and Week 10
Ankle Eversion Test Range of Motion at 60°/s
Time Frame: Baseline, Week 5, and Week 10
Range of motion recorded by the isokinetic dynamometer during the eversion test performed at 60°/s, expressed in degrees. This measure represents the angular range recorded during the corresponding isokinetic testing condition.
Baseline, Week 5, and Week 10
Ankle Inversion Test Range of Motion at 120°/s
Time Frame: Baseline, Week 5, and Week 10
Range of motion recorded by the isokinetic dynamometer during the inversion test performed at 120°/s, expressed in degrees. This measure represents the angular range recorded during the corresponding isokinetic testing condition.
Baseline, Week 5, and Week 10
Ankle Eversion Test Range of Motion at 120°/s
Time Frame: Baseline, Week 5, and Week 10
Range of motion recorded by the isokinetic dynamometer during the eversion test performed at 120°/s, expressed in degrees. This measure represents the angular range recorded during the corresponding isokinetic testing condition.
Baseline, Week 5, and Week 10

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.
Yuanyan Huang

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 (Actual)

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.
July 5, 2024

Primary Completion (Actual)

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.
September 20, 2024

Study Completion (Actual)

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.
September 20, 2024

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).
September 4, 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.
September 4, 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.
September 10, 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.
September 10, 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.
September 4, 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.
September 1, 2026

More Information

Terms related to this study

Keywords

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.
  • 2024-0666-001
  • P01-202407-01-004 (Other Identifier: Public Institutional Bioethics Committee, Republic of Korea)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

De-identified individual participant data that support the findings of the study may be shared with qualified researchers upon reasonable request, subject to applicable ethical and data-protection requirements.

IPD Sharing Time Frame

Beginning after publication of the primary study results, with no predetermined end date.

IPD Sharing Access Criteria

De-identified individual participant data may be shared with qualified researchers upon reasonable request for scientifically appropriate purposes. Requests should include a brief research proposal and planned analyses and will be reviewed for ethical, privacy, and data-protection considerations. Approved data will be provided by the study investigator.

IPD Sharing Supporting Information Type

  • STUDY_PROTOCOL

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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