The purpose of the study was to investigate how the timing of application of vibration to the arm muscles affects grip force. Eight healthy subjects performed similar tasks of lifting and holding an object without any vibration (NV) and with vibration applied to the extrinsic wrist and finger muscles at different times during the task: 1) applied immediately prior to the task performance (AFV) and 2) during the task performance (DFV). Peak grip force, static grip force, and acceleration of the object were recorded. Vibration applied to the muscles during the task performance did not affect grip force generation. However, when vibration was applied prior to the task performance, a significant increase in grip force was observed. We suggest that the differences in magnitudes of grip force between the conditions are associated with the availability of information from muscle spindles and/or joint and tactile afferents. It appears that vibration applied during the task performance affects only muscles spindles, while a five-minute vibration applied prior to the lift of the object affects both muscle spindles and joint and tactile afferents. The results of the study provide additional information on the availability of afferent information in the control of grip force.