Sympathetic Stress and Whole Body Vibration Reflex
Condition: Vibration; Exposure; Muscle Physiology
Study type: Interventional

Summary: 
      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: 
      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.
    

Intervention name(s): Vibration
Intervention type(s): Procedure
Intervention description(s): whole-body vibration, and tendon vibrations will be applied to the human body
Other intervention name(s): whole body vibration; tendon vibration; sympathetic activation maneuver
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: tonic vibration reflex; vibration; whole body vibration; sympathetic activation