Exploratory study on the impacts of handle vibration on the hand and forearm

This study investigated the immediate impacts of short-term handle vibration on hand functions, upper limb discomfort, and forearm muscle responses during hand grip test and task performance of seven healthy young adults. The task was to grip the handlebar for 5 minutes with 50% perceived strength under two conditions: with handle vibration (HV) and without handle vibration (NHV). Activities of forearm muscles namely flexor carpi radialis (FCR), flexor of the fingers (FF), flexor carpi ulnaris (FCU), and extensor digitorum (ED) were recorded using surface electromyography (EMG), while post-task hand tests for finger dexterity, strength, and sensibility were also measured. These finger functions as well as muscle responses did not differ significantly between HV and NHV. The lacking effects might be associated to the inconsistencies on grip force during task, perhaps participants let go of the handle during the latter part. Meanwhile, perceived discomfort on the shoulder was significantly higher after HV than NHV and activity of FCR, FF, and ED during maximal grip test were significantly different (p < 0.05) as well. Specifically, muscle activities were lower by 12-15% after HV than NHV, indicating that HV might have influenced the ability to grip hardly. In conclusion, maximal grip test and discomfort rating can be a predictive parameter to determine the instantaneous effects of handle vibration.