Hotspot determination and motor threshold determination (15 minutes): The target with the greatest motor evoke potential (MEP) peak-to-peak amplitude will be defined as the hotspot which is the most responsive location on the motor cortex. After determining the hotspot, the motor threshold (MT) will be assessed over the hotspot. We define the resting MT as the minimal TMS output necessary to produce MEPs with a peak-to-peak amplitude >50 microvolts in at least 3 out of 5 consecutive trials. EMG signal will be recorded using surface electromyography (EMG) electrodes attached over bilateral biceps based. All data will be collected by a custom EMG amplifier and data acquisition system and stored by LabVIEW program (National Instruments, Austin, TX) for offline analysis.