Acute physiological and functional effects of repetitive shocks on the hand–arm system: a pilot study on healthy subjects

Objectives. Exposure to hand-transmitted shocks is a widespread phenomenon in the workplace. Separate risk assessments for shocks do not exist in current international hand–arm vibration regulations, leading to potential underestimation of associated health risks. Methods. In a pilot study approach, eight healthy males were exposed to sets of 3 × 5 min of repetitive shocks and 1 × 5 min of random vibration, controlled at a weighted vibration total value of 10 m/s². Baseline and post-exposure measurements of vibration perception thresholds, finger skin temperature, maximal grip/pinch force and the Purdue pegboard test were conducted. Muscle activity was monitored continuously by surface electromyography. Results. Shock exposures evoked a temporary increase of vibration perception thresholds with high examination frequencies. A decrease of skin temperature was hinted for shocks of 1 and 20 s^–1. Electromyographical findings indicated an additional load on two forearm muscles during shock transmission. Maximum grip force and manual dexterity were not affected, and pinch force only partially reduced after the exposures. Conclusion. Physiological effects from shock exposure conform to those described for hand–arm vibration exposure in principle, although some divergence can be hypothesized. Randomized designs are required to conclusively assess the need of occupational health concepts specifically for hand-transmitted shocks.