Electromyography (EMG) has been proposed as a method for determining muscle effort in repetitive upper limb tasks, which are often related to cumulative trauma disorders. EMG activity of the finger flexor musculature was investigated during a repetitive hand gripping task having 5 different cycle durations (2 to 6 s), various percentage of work time (and rest) within the work cycle (20% to 80%), and 3 different grip force levels. Thirty healthy adult participants each performed 27 randomly ordered 30-s repetitive hand gripping trials as well as 3 isometric contractions, which were used to normalize data from the hand gripping trials. There was a significant decrease in mean EMG as the duration of the work-rest cycle time increased. At each force level, EMG increased as the percentage of work time within the work-rest cycle increased, but to a greater extent at the highest force level. The results of this study suggest that overall muscle effort, and perhaps muscle fatigue, can be reduced most effectively by modifying the force requirements of the repetitive task. Other variables, such as the percentage of work time within a cycle and overall work cycle time have less effect on the EMG activity level. The results of this study have implications for developing strategies to reduce muscle fatigue during repetitive hand gripping tasks in an effort to reduce the effects of cumulative trauma disorders.

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Work rate and relative exercise intensity are basic considerations in developing optimal exercise training prescriptions in cardiopulmonary rehabilitation. Velocity and energy cost of walking are directly related to work rate and indirectly related to exercise intensity. This article describes two methods of measuring walking velocity and estimating oxygen uptake. The validity and accuracy of the methods are discussed. We believe both methods are clinically useful. Because one method uses a specially instrumented speedometer cane, technical information concerning its design and construction is also included.

A computerized method for assessing standing posture was described and evaluated. As experimentally determined, the precision of the method was to the nearest millimeter. The accuracy (measurement error) of the system was 1.0% for the X direction, 3% for the Y direction, and 2.6% for the Z direction. Using 32 subjects the intraday and interday reliability was good. The validity of the method was satisfactory for acquiring measurements of the spinal column.

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