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This study aims to investigate how standing posture and mechanical loading affect reflex responses in the lower limb. Specifically, it focuses on the H-reflex-a type of spinal cord reflex-and how it changes during quiet standing and whole-body vibration. Ten healthy adult volunteers will participate. Researchers will record electrical responses from the calf muscle (soleus) while participants stand still or are exposed to gentle vibration. The goal is to better understand how the nervous system and skeletal system interact in regulating balance and movement.
This study investigates the neural mechanisms responsible for suppression of the H-reflex-a spinal monosynaptic reflex-during mechanical loading in the standing position. Previous research has shown that H-reflex amplitude decreases with increasing postural demand, such as during walking or standing compared to lying down. One hypothesis suggests that this suppression may be mediated not only by vestibular and cutaneous afferents, but also by a bone-derived reflex mechanism called the Bone Myoregulation Reflex (BMR).
In this study, 10 healthy adult volunteers will undergo H-reflex measurements while standing in various loading conditions, including quiet standing and during whole-body vibration (WBV). Participants will stand with one foot isolated from vibration while the other foot is on a vibrating platform. H-reflexes will be recorded from the soleus muscle using standard surface electromyography.
The primary aim is to determine whether BMR contributes to H-reflex suppression during loading. The findings may provide insight into the interaction between skeletal loading and spinal reflex modulation, with potential relevance to balance, gait, and rehabilitation science.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Postural Loading and Vibration Arm | Experimental | Participants in this arm will undergo a sequence of experimental conditions involving postural and mechanical loading. The protocol includes standing quietly on both feet, standing on one foot (right or left), and standing during whole-body vibration (WBV). H-reflex recordings will be obtained from the soleus muscle during each condition to assess changes in spinal reflex excitability. |
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| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Whole-Body Vibration (WBV) | Procedure | Participants will stand quietly in an upright position while whole-body vibration (WBV) is applied through a vibration platform. The vibration stimulus is delivered while the participant's left foot remains on the vibration surface and the right foot is elevated or isolated. H-reflex recordings are taken from the soleus muscle during the procedure to assess spinal reflex modulation due to mechanical loading. |
| Measure | Description | Time Frame |
|---|---|---|
| H-reflex Amplitude | The amplitude of the H-reflex recorded from the soleus muscle, evoked at 15% Mmax stimulation level, will be measured during each condition (quiet standing, one-leg stance, and whole-body vibration). The primary aim is to assess changes in spinal excitability due to mechanical loading. | Day 1 (single-session, during each experimental condition) |
| Measure | Description | Time Frame |
|---|---|---|
| Background EMG Activity | Background electromyographic activity of the soleus muscle will be evaluated over a 450 ms window prior to stimulation to ensure muscle quiescence and verify that changes in reflex amplitude are not due to background activity. | Day 1 (450 ms window prior to stimulation) |
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Inclusion Criteria:
Exclusion Criteria:
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| Name | Affiliation | Role |
|---|---|---|
| Selim Sezikli, MD | Istanbul Physical Medicine and Rehabilitation Training and Research Hospital | Principal Investigator |
| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Istanbul Physical Medicine and Rehabilitation Training and Research Hospital | Istanbul | Istanbul | Turkey (Türkiye) |
| PubMed Identifier | Type | Citation | Retractions |
|---|---|---|---|
| 42423762 | Derived | Ozkan IA, Alayoglu FO, Kalaoglu E, Dogan N, Yildiz N, Yurtseven M, Ones K, Karacan I, Turker KS. Load-dependent dissociation between H-reflex amplitude and background EMG activity during oscillatory loading: implications for the bone myoregulation reflex. Exp Brain Res. 2026 Jul 9;244(8):154. doi: 10.1007/s00221-026-07349-z. |
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Individual participant data will not be shared due to the small sample size and the nature of the study, which focuses on basic physiological measurements in healthy volunteers. No data repository is currently planned.
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Single-group crossover design in which each participant undergoes all experimental conditions in a fixed order, including quiet standing, weight-shifting, and whole-body vibration. Electrophysiological recordings are obtained during each condition.
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