Computer-assisted hand-held dynamometer: low-cost instrument for muscle function assessment in rehabilitation medicine.

In rehabilitation medicine, muscle function is assessed during the physical examination of the patient. Although a simple hand-held instrument improves the assessment of static strength, it is rarely used in clinical practice, where dynamic measurements are preferred. A computer-assisted hand-held dynamometer (CAHNDY) has been developed that enables the clinician to measure dynamic muscle function in a standardised manner, using simple (i.e. portable and low-cost) apparatus. The CAHNDY comprises a force transducer and a movement transducer interfaced to a personal computer. In the study dynamic measurement protocols are used, based on a biomechanical analysis of daily activities. In this way, iso-functional profiles can be established, describing the kinematics of muscle function in its functional context. Using the iso-functional profiles as a basis for standardisation, the double feedback algorithm of the CAHNDY assists the tester in meeting this standard, during maximal muscle function testing. In a multi-centre trial, the CAHNDY is evaluated by physical therapists for knee extensor and flexor function. The CAHNDY enables iso-functional dynamic muscle function testing, although application is limited by the maximal strength of the tester. It is concluded that the CAHNDY is suitable for use in rehabilitation medicine.