H-reflex, Spinal Reflexes, Posture, Weight-Bearing, Neuromuscular Physiology
Conditions
Keywords
Bone Myoregulation Reflex, Whole-Body Vibration, Electrophysiology, Soleus Muscle, Presynaptic Inhibition, Mechanoreceptors, Reflex Suppression
Brief summary
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.
Detailed description
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.
Interventions
PROCEDUREWhole-Body Vibration (WBV)
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.
Sponsors
Istanbul Physical Medicine Rehabilitation Training and Research Hospital
Study design
Allocation
NA
Intervention model
SINGLE_GROUP
Primary purpose
BASIC_SCIENCE
Masking
NONE
Intervention model description
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.
Eligibility
Sex/Gender
ALL
Age
20 Years to 45 Years
Healthy volunteers
Yes
Inclusion criteria
* Healthy adults aged 20 to 45 years * Able to stand independently for at least 10 minutes * No known neurological, orthopedic, or balance disorders * Willingness to participate and provide informed consent
Exclusion criteria
* History of spinal cord injury, peripheral neuropathy, or muscle disease * Recent lower limb surgery or musculoskeletal trauma * Current use of medications affecting neuromuscular function * Pregnancy * Any contraindications to exposure to mechanical vibration
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| H-reflex Amplitude | Day 1 (single-session, during each experimental condition) | 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. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Background EMG Activity | Day 1 (450 ms window prior to stimulation) | 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. |
Countries
Turkey (Türkiye)
Outcome results
None listed