Load Dependent Modulation of Spinal Excitability: Linking H-Reflex Supression and Whole Body Vibration Induced Reflex Latency

Study Results

Results pending

The study team has not published outcome measurements, participant flow, or safety data for this trial yet. Check back later for updates.

Basic Information

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Recruitment Status

RECRUITING

Clinical Phase

NA

Total Enrollment

15 participants

Study Classification

INTERVENTIONAL

Study Start Date

2025-11-21

Study Completion Date

2025-12-30

Brief Summary

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This study examines how different standing postures and whole-body vibration conditions affect spinal reflex activity. Participants will stand in various positions-with and without vibration of two amplitudes-and H-reflex responses from the soleus muscle will be recorded. Additionally, vibration-induced reflex latency will be assessed across multiple vibration frequencies.

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Detailed Description

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Participants will engage in a structured set of experimental tasks designed to evaluate the effects of postural mechanical loading, and whole-body vibration.

The protocol includes four primary standing conditions:

Quiet bipedal stance,

Single-leg stance on the left side,

Bipedal stance during whole-body vibration (WBV), and

Single-leg stance on the left side during WBV.

During all WBV conditions, two vibration amplitudes-2.2 mm and 1.2 mm-will be applied sequentially to assess amplitude-dependent modulation of reflex responses.

Throughout each condition, H-reflex recordings from the soleus muscle will be collected to quantify changes in spinal reflex excitability under varying postural and vibratory loads. In addition to these measurements, vibration-induced reflex latency will be evaluated by delivering vibratory stimuli at multiple frequencies (30, 32, 34, and 36 Hz) within the same experimental protocol. This approach allows for a comprehensive analysis of how both posture and vibratory parameters influence neuromuscular reflex pathways.

The investigators conducted an a priori power analysis for a repeated-measures ANOVA (within-subjects design) to determine the required sample size. The analysis was based on a medium expected effect size, specified as partial eta squared (ηₚ²) = 0.06, which corresponds to an effect size of f = 0.25. The investigators set the alpha error probability at 0.05 and the desired statistical power (1-β) at 0.80. The design included one group with five repeated measurements, assuming a correlation of 0.70 among repeated measures. Under these conditions, the critical F value was 2.5652405, with 4 numerator degrees of freedom and 48 denominator degrees of freedom. The power analysis indicated that a total sample size of 13 participants is required. The required sample size was calculated using G\*Power version 3.1.9.4 (Franz Faul, University of Kiel, Germany).

Conditions

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Vibration H-reflex

Study Design

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Allocation Method

NA

Intervention Model

SINGLE_GROUP

Primary Study Purpose

BASIC_SCIENCE

Blinding Strategy

NONE

Study Groups

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Healthy participants

Participants will complete a series of experimental tasks involving postural mechanical and vibrational loading. The protocol consists of quiet standing on both feet, single-leg standing on the left side, standing during whole-body vibration (WBV), and single-leg standing on the left side during WBV. Vibration amplitudes of 2.2 mm and 1.2 mm will be applied in each condition. H-reflex measurements will be recorded from the soleus muscle throughout all tasks to evaluate alterations in spinal reflex excitability. Vibration induced reflex latency will be also measured with different vibration frequencies (30-32-34-36) also measured in the same protocol.

Group Type EXPERIMENTAL

Whole Body Vibration

Intervention Type OTHER

Whole Body Vibration (WBV) is a neuromuscular training modality in which patients stand, sit, or exercise on a platform that delivers mechanical oscillations (30-36 Hz, 1-2 mm amplitude). While WBV is applied H-Reflex tests are done.

Interventions

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Whole Body Vibration

Whole Body Vibration (WBV) is a neuromuscular training modality in which patients stand, sit, or exercise on a platform that delivers mechanical oscillations (30-36 Hz, 1-2 mm amplitude). While WBV is applied H-Reflex tests are done.

Intervention Type OTHER

Eligibility Criteria

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Inclusion Criteria

* Healthy adults between 25 and 50 years of age
* Individuals willing to participate and able to provide informed consent
* Individuals who can stand independently for at least 10 minutes
* Participants with no known neurological, orthopedic, or balance impairments