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

Summary: 
      Whole-body vibration (WBV) has beneficial neuromuscular effects on muscle strength increase.
      Supraspinal, spinal, and peripheral mechanisms have been proposed to explain these beneficial
      effects. The most commonly proposed explanatory mechanism is spinal segmental reflexes.
      However, the neuronal circuit and receptors of the reflex response have not been defined
      precisely. A group of researchers found that the reflex system is the Tonic vibration reflex
      (TVR) under the neuromuscular effects of WBV; Other researchers claim that WBV activates a
      different spinal reflex than TVR. Tonic vibration reflex is a polysynaptic reflex that occurs
      as a result of muscle spindle activation, in which more than 100 Hz vibrations are applied to
      the belly or tendon of the muscle. A group of researchers argues that WBV activates the
      spinal reflex response, but this reflex response is different from TVR. According to them,
      WBV-induced reflex (WBV-IR) response latency is longer than TVR latency. WBV activates TVR at
      very attenuated amplitude; WBV activates a different spinal reflex with longer latency at
      medium and high amplitude vibration. They reported that although the H-reflex, T-reflex, and
      TVR latency was longer in the spastic soleus muscle than normotonic soleus muscle, where the
      muscle spindle and Ia afferent pathway were hyperactive. However, the WBV-IR latency was
      similar in both spastic and normotonic soleus muscle. According to our hypothesis, the reflex
      system activated by WBV changes depending on vibration frequency: if the high-frequency
      (100-150 Hz) WBV is applied, the tonic vibration reflex is activated; if the low-frequency
      (30-40 Hz) WBV is applied, the bone myoregulation reflex is activated. The purpose of this
      research is to test this hypothesis.
    

Detailed description: 
      Seven healthy recreationally active males between the ages of 26 and 35 volunteered to
      participate in this study. All subjects received pre-study informed consent. All experimental
      procedures were designed with the Helsinki declaration in mind and approved by the local
      ethics committee. All subjects performed a familiarization trial to acclimate subjects to the
      WBV stimulus. WBV-IR and TVR latency of soleus muscle were then measured in the quiet
      standing position. The vibrations (WBV or tendon) sequence were applied randomly to negate
      any order/time effect. The subject rested for five minutes between the WBV and tendon
      vibration. The WBV application was delivered using a PowerPlate Pro5 device (PowerPlate
      International, Amsterdam, The Netherlands). First, 30 Hz, low amplitude (1 mm) vibration with
      a duration of 30 seconds was applied to each subject for familiarization purposes. After
      three minutes of rest, low-amplitude (1 mm) WBV testing was performed in random order in
      quiet standing positions. In a WBV set, three different vibration frequencies (30, 35, and 40
      Hz), each lasting for 30 s with 3-s rest intervals, were delivered. The local vibration was
      applied to the mid-point of the right Achilles tendon by using a custom-made vibrator. The
      head of the tendon vibrator was in light contact with the underlying skin. Tendon vibrations
      were applied by the same researcher. Three different vibration frequencies (100, 135, and 150
      Hz) were delivered, lasting for 30 s with 3-s rest intervals. A local vibration was applied
      to the right heel using the same custom-made vibrator. Tendon vibrations were applied by the
      same researcher. Three different vibration frequencies (100, 135, and 150 Hz) were delivered,
      lasting for 30 s with 3-s rest intervals.

      The surface electromyography (SEMG) recorded from the soleus and acceleration data were
      collected simultaneously using data acquisition and analysis system (PowerLab ® software,
      ADInstruments, Oxford, UK). Disposable self-adhesive bipolar Ag/AgCl (Covidien Kendall,
      Dublin, Ireland) surface electrodes were placed on the right soleus belly 4 cm apart. The
      skin overlying the muscle was shaved, light abrasion was applied, and the skin was cleaned
      with alcohol to reduce the skin resistance. To determine TVR latency, a light (2.9 g)
      piezoelectric accelerometer (LIS344ALH, ECOPACK®, Mansfield, TX, USA) was firmly fixed using
      adhesive tape on the skin overlying the right Achilles tendon. To determine WBV-IR latency,
      an identical accelerometer was firmly mounted on the WBV platform. The acceleration and SEMG
      signals were recorded at a sampling frequency of 20 kHz. Accelerometer recordings were
      filtered with a high-pass filter set at 5 Hz. SEMG data obtained during WBV were bandpass
      filtered at 80-500 Hz to reduce vibration-induced movement artifacts and then full-wave
      rectified. Similarly, SEMG data obtained during tendon vibration were bandpass filtered at
      160-500 Hz and then full-wave rectified. WBV-IR and TVR latencies were then calculated by
      using the cumulative average method.

      An electronic reflex hammer (Elcon, Germany) was used to determine T-reflex latency. All
      latencies were normalized to the body height of each participant.

      Latency was expressed as milliseconds (ms).
    

Intervention name(s): vibration
Intervention type(s): Procedure
Intervention description(s): whole-body vibration, heel and soleus tendon vibrations were applied to the human body
Intervention model: Single Group Assignment
Intervention model description: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: muscle strength; vibration; tonic vibration reflex