 During tactile stimulation, the investigator will place hisher middle 2 or 3 fingers on the lumbar multifidus at L5-S1 between the 2 electrodes before the verbal instruction is given. The investigator will then give the same verbal instruction and ask the participant to perform the contralateral-arm-lift task while maintaining finger contact on the multifidus muscle during muscle activation. EMG testing will start after the verbal instruction is completed. 