Dynamic Stability, Postural Control
Conditions
Keywords
water-inertia loading, unstable-load training, healthy young women, dynamic stability training, dynamic balance, postural control, Y-Balance Test, center of pressure, single-leg stance
Brief summary
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.
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.
Interventions
BEHAVIORALWater-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.
BEHAVIORALStable-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.
Sponsors
Yuanyan Huang
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
OTHER
Masking
SINGLE (Outcomes Assessor)
Eligibility
Sex/Gender
FEMALE
Age
19 Years to 25 Years
Healthy volunteers
Yes
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.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Normalized Anterior Reach Distance on the Y-Balance Test | 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. |
| Normalized Posteromedial Reach Distance on the Y-Balance Test | 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. |
| Normalized Posterolateral Reach Distance on the Y-Balance Test | 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. |
| Y-Balance Test Composite Score | 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. |
| Center-of-Pressure Total Distance During Eyes-Open Single-Leg Stance | 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. |
| Anteroposterior CoP RMS During Eyes-Open Single-Leg Stance | 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. |
| Mediolateral CoP RMS During Eyes-Open Single-Leg Stance | 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. |
| Center-of-Pressure Total Distance During Eyes-Closed Single-Leg Stance | 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. |
| Anteroposterior CoP RMS During Eyes-Closed Single-Leg Stance | 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. |
| Mediolateral CoP RMS During Eyes-Closed Single-Leg Stance | 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. |
| Knee Extension Peak Torque Relative to Body Weight at 60°/s | 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. |
| Knee Flexion Peak Torque Relative to Body Weight at 60°/s | 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. |
| Ankle Inversion Peak Torque Relative to Body Weight at 60°/s | 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. |
| Ankle Eversion Peak Torque Relative to Body Weight at 60°/s | 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. |
| Ankle Inversion Peak Torque Relative to Body Weight at 120°/s | 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. |
| Ankle Eversion Peak Torque Relative to Body Weight at 120°/s | 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. |
Countries
South Korea
Outcome results
None listed