Abstract
The silent period is an inhibitory period, which is induced by stimulating the continuous contractive muscle. The variation of the silent period is provided by facilitatory condition of central nervous system. This study is the preliminary research of facilitatory condition of central nervous system during some sports activity. The study was performed on the soleus muscles of healthy non-athletes (20 lower extremities of 8 healthy males and 2 females, mean age 25.2±2.72; range 22-32 years and mean height 169.6±8.60; range 152-182 cm). The silent period was recorded as follows: subjects were in supine position with the hip and knee joints of the recorded side flexed at 45 degrees, and with the ankle joint kept 0 degree. Isometric contraction levels were 25, 50, 75 and 100% of maximal effort. Electrical stimulation (intensity: supra-maximal, duration: 0.2 ms; frequency: 0.5 Hz) was administered to popliteal fossa of tibial nerve. Recording electrode was placed on the soleus muscle and the reference electrode on the ipsilateral Achilles tendon, and samplings were repeated 20 times.
The results indicated that silent period was the shortest during 75% of maximal effort. Similar to the results of upper extremity, it was considered that the cortical inhibition was mostly released during sub-maximal effort level; in other words, central nervous system was mostly facilitated during sub-maximal effort.
