Grasping and manipulating objects require versatile control of grip forces. Central nervous system injury or disease can result in the loss of sensory and motor functions in the upper extremities, resulting in reduced hand functionality.
Objective assessment is needed to monitor and quantify patient’s progress during the therapy, and to validate the effects of the treatment. In clinical practice, dynamometers are used to measure maximal voluntary grip force; however, simple dynamometers cannot provide information about submaximal force control. For measurement of motor control capability in submaximal forces, force tracking tasks are suitable.
The HandForce prestige™ device is designed to combine measurement of maximal grip force control and hand force tracking tasks in one system. The device is equipped with two grasp measuring units, which are similar to objects used in daily activities, allowing the assessment of functional gripping forces. Unit 1 has a shape of a cylinder and is used to measure cylindrical grip (power grip), and can measure forces up to 300 N. Unit 2 is made up of two metal parts which shape into a thin plate at the front end and is used to measure lateral grip (precision grip). Unit 2 has a range of 0 to 150 N.
The patient’s maximal grip force and force tracking data are automatically stored after each task is performed. The performance of the tracking is quantified by calculating relative tracking error between the target signal and the measured response. The HandForce system has four different tracking signals: sinusoidal, sinusoidal with linear varying frequency, traingular and rectangular shaped signals. The tracking task requires of the patient to track the target signal on the screen as closely as possible by applying appropriate force to grip measuring unit.
The system also allows graphical representation of all measured data. The selected data are presented for the last ten measurements. The HandForce system also enables patient’s data to be transferred as text file (txt) to the PC via USB mass storage device.