If the EMG signal contained too much noise because of body hair, the body hair was removed. Ag-Cl bipolar EMG electrodes (Norotrode 20 TM, Myotronics-Noromed, Inc., WA, USA) were attached
to the muscle belly in a direction parallel to the muscle fibers.After attaching the base electrode to the fibular head,the surface EMG equipment was connected. With the subjects relaxed, after confirming that the noise level was below 1μV in an EMG noise test, EMG recording was started.