*2.1.2. Inhibitory act on muscle contraction*

When skeletal muscle during a maximum contraction receives vibration stimulation, the muscle's action potential on EMG, nerve activity, and muscle output are reduced (Bongiovanni 1989, Kouzaki 2000, Stephen 2003, Konishi 2009). The inhibitory effect of muscle contraction is dependent on the conditions of vibration stimulation: the effect is greater if the frequency of the vibration stimulation is low, or if its amplitude is large (Desmedt 1978).

In recent reports, when stroke patients with a spastic upper limb received vibration stimulation on the limb, their upper limb function was shown to improve with a suppression of muscle tone (Noma 2012, Caliandro 2012).

In patients who underwent ACL reconstructive surgery or those with osteoarthritis, vibration stimulation to their quadriceps femoris muscle brought about neither an increase in neural activity as evaluated by integrated EMG nor a decrease in muscle output as evaluated by peak torque (Konishi 2002, Rice 2011). It is thought that this outcome was due to a failure in Ia afferent feedback, including dysfunction of the gamma-loop.
