Employees are wearing large bulky cotton gloves during the operation which create resistance to finger movement. In addition, poorly fitting cloth gloves require more force production by the fingers and hands to overcome decreases in friction and tactile sensitivity. Make sure gloves fit properly, offer minimal resistance to finger movement, and do not decrease the tactile sensitivity. Gloves should be made of a material which increases the coefficient of friction between the hand and the load surface. This will reduce the hand and finger force required to perform a particular repetitive task.
Impact wrenches are heavy and have only a single handle for activation and control.
The tool appears to have a metal case with a low coefficient of friction. The employee is more apt to use only one hand when operating the tool if it has a handle with only one hand position. This increases the chance of fatigue and injury in the support arm and increases the amount of instability over a tool which has support mechanisms for two handed use. In addition, one handed use and a handle with a low coefficient of friction increases the amount of finger force required to maintain control of the tool. Either purchase tools, or retrofit existing tools, with handles which have a high coefficient of friction to facilitate tool control without exertion of extreme finger force.