Sympathetic Stress and Whole Body Vibration Reflex

Study Overview
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Brief Summary
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Whole body vibration (WBV) is a therapeutic modality in the form of exercise on a vibrating platform with an amplitude of 2-4 mm at a frequency of 25-50 Hz, which is used with increased popularity in sports medicine and rehabilitation due to its beneficial effects on muscle strength, balance, postural control, bone formation, and circulation. Beneficial effects on muscle strength and athletic performance have been reported. Spinal reflexes explain these beneficial neuromuscular effects. However, the neuronal circuit and receptors of the reflex response have not been defined precisely. A group of researchers propose that the reflex system underlying the neuromuscular effects of WBV is the Tonic vibration reflex (TVR), whose receptor is the muscle spindle; other researchers claim that the reflex latency induced by WBV is 4-5 ms longer than the TVR latency, so it is a bone myoregulation reflex whose receptor is osteocytes. The muscle spindle has sympathetic innervation. It has been reported that in case of increased sympathetic activity, muscle spindle sensitivity may increase and short-latency stretch reflex may be facilitated. The variation of muscle spindle activity with sympathetic activity may provide an opportunity to define the nature of the reflex response during WBV. Muscle spindles are more sensitive to vibrations around 100 Hz. This study has two hypotheses: According to the first hypothesis, WBV activates muscle spindles and the reflex latency induced by WBV is the same as TVR latency, and the latency does not change with increased sympathetic activity. According to the alternative hypothesis, WBV activates osteocytes, and WBV-induced reflex latency is longer than TVR latency. With increased sympathetic activity, the WBV reflex becomes dominant and the WBV-induced reflex latency becomes shorter. The aim of this research is to determine which of these two hypotheses is valid.

Detailed Description
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22 healthy males between the ages of 20 and 45 will be recruited for this study. All subjects will receive pre-study informed consent. All experimental procedures were designed with the Helsinki declaration in mind and approved by the local ethics committee. In all subjects, whole body vibration(WBV) and isolated tendon vibration will be applied before, after, and during sympathetic activation maneuvers. Reflex responses induced by WBV and isolated tendon vibration will be recorded by surface electromyography (EMG) from the right soleus muscle. Latency calculation will be made using the Cumulative averaging method. Mental arithmetic task and cold stress test will be applied as sympathetic activation maneuver. For the mental arithmetic task, the subject is asked to mentally subtract a two-digit number from a four-digit number and respond within five seconds. This arithmetic calculation is repeated for different numbers. This test is continued for two minutes. For the cold stimulation test, subjects are asked to dip their right hand into 2-4 degrees cold water up to the elbow and hold it in the water for two minutes. At this time, either WBV or tendon vibration will be applied. After a ten-minute break, a cold stimulation test will be applied to the left hand and the subject will be asked to do mental arithmetic calculations simultaneously. Meanwhile, other vibrations will be used. The sympathetic response will be evaluated by heart rate and sympathetic skin response. Whole body vibration will be applied to the right leg while subjects are sitting with their knee, hip, and ankle joints in a 90-degree position. The left leg will rest on a vibration-isolated platform. During this position, he will be asked not to voluntarily contract the calf muscle. The vibration will be applied with the PowerPlate® Pro5 WBV (London UK) device. The vibration amplitude will be 2.2 mm. The vibration frequency will be 30, 35, 40, and 45 Hz. Each vibration frequency will be applied for 30 seconds. A 5-second rest period will be applied between 30-second vibrations. Piezo-electric accelerometer (LIS344ALH, full-scale of ± 6 g, linear accelerometer, ECOPACK®, Mansfield, TX, USA) will be fixed on the WBV device platform for reflex latency calculation. For tonic vibration 100, 135, 150, and 180 Hz vibrations will be applied to the Achilles tendon. 30 seconds of vibration will be applied at each frequency. A direct current (DC) motor vibrator will be used to apply this vibration (Bosch™, amplitude 2 mm, motor speed 5000-20000 / min). A piezo-electric accelerometer (LIS344ALH, full-scale of ± 6 g, linear accelerometer, ECOPACK®, Mansfield, TX, USA) will be placed on the skin of the Achilles tendon to calculate the tonic vibration reflex latency. Superficial EMG recordings will be taken from the right soleus muscle with the bipolar technique. A pair of self-adhesive Ag/AgCl (KENDALL® Coviden, Massachusetts, USA) electrodes will be attached to the skin. The electrodes on the soleus will be positioned according to the SENIAM protocol. The ground electrode will have adhered to the right lateral malleolus. Before the electrodes are attached to the skin, if there are hairs on the skin, they will be shaved and the oil layer on the skin will be cleaned with alcohol cotton. In order to increase the moisture of the skin, ECG gel will be applied to the skin area where the electrode will be attached. Superficial EMG recordings will be taken with a PowerLab ® (ADInstrument ADInstruments, Oxford, UK) data recorder with a sample rate of 40 kHz. EMG recordings will be analyzed offline with LabChart7 Pro® version 7.3.8 (ADInstrument, Oxford, UK). The acceleration measurement data will be recorded with the PowerLab (ADInstrument London) data logger simultaneously with the EMG recording. Acceleration recording will be made with a sample rate of 40 kHz. Simultaneously, heart rate and sympathetic skin response will be captured with a Biopac (Biopac System Inc CA) data recorder at a rate of 20 kHz.

Official Title
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Effect of Sympathetic Stress on Whole Body Vibration Reflex

Conditions
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Vibration; Exposure, Muscle Physiology

Intervention / Treatment
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* Procedure: Vibration


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Being healthy Being a young adult (20-45 years old) Volunteer Male Exclusion Criteria: Scar, dermatitis, etc. in the skin tissue where EMG electrodes will be placed Kidney stone history Fracture in the lower extremity, history of orthopedic surgery Heart disease, Hypertension Dizziness Metabolic bone diseases, including osteoporosis History of bone occupying lesion, neoplasia, osteomyelitis Degenerative, inflammatory diseases of the joints of the lower extremities Lower extremity thrombophlebitis Lower extremity motor loss, sensory loss, muscle atrophy Cold allergy Subjects who cannot tolerate whole-body vibration

Ages Eligible for Study
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Minimum Age: 20 Years
Maximum Age: 45 Years

Sexes Eligible for Study
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Male

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Vibration group<br>Vibration (WBV, and tendon vibration) and sympathetic activation maneuvers will be applied to participants | Procedure: Vibration<br>* whole-body vibration, and tendon vibrations will be applied to the human body<br>* Other names: sympathetic activation maneuver;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Whole-body vibration (WBV) induced reflex latency | Latency of the soleus reflex response induced by WBV. Its unit is milliseconds | during intervention, an average of 3 minute | 
| Tendon vibration induced reflex latency | Vibration will be applied to the achilles tendon. The soleus reflex latency induced by the tendon vibration will be measured. Its unit is milliseconds | during intervention, an average of 3 minute | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Heart rate variability | Heart rate variability will be measured to determine sympathetic activity. Low-frequency (LF) and high-frequency (HF) were considered to reflect sympathetic and parasympathetic activity, respectively. The autonomic balance was obtained by the ratio between the sympathetic and parasympathetic areas (LF/HF); wherein ratios >1, <1, and 1 were indicative of sympatheticotonia, vagotonia, and sympathovagal balance, respectively. | during intervention, an average of 2 hours | 
| Sympathetic skin response | Sympathetic skin response will be measured to determine sympathetic activity.Unit is milliVolt | during intervention, an average of 2 hours | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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tonic vibration reflex, vibration, whole body vibration, sympathetic activation