a bipolar electrode configuration, and inter-electrode spacing was consistent between channels and between subjects (4.8 cm) as limited by the collar to collar dis tance. Although this spacing was larger than usual, it was deemed adequate in order to study global muscle behav ior under the electrode sites, and allowed for the elec trodes to be placed over the muscle groups of interest without recording excessive crosstalk from synergist or antagonist muscles. Two reference electrodes were used, as required by the design of the data recorder. The neck and low back channels used a common reference elec trode at the T7 spinous process, and the shoulder and forearm channels used a common reference at the medial epicondyle of the humerus. Fig. 1demonstrates this elec trode configuration, and the portable data acquisition system. Electrodes were applied a minimum of 10min prior to the initiation of data collection, allowing time for the electrode-tissue impedance to stabilize to an accept able level (Parker and Scott, 1969). The data acquisition system had a pass-band of 10-800Hz, and a sampling rate of 1024Hz per channel, in accordance with the International Society of Electrophysiology and Kinesiol ogy (ISEK) standards on the acquisition of myoelectric signal data (ISEK, 2000). The analog-to-digital conver sion (A/D) was done using an 8 bit fixed point processor, and was programmed in TMS 320 Assembler language. As the resolution of the A/D was not ideal, the channel gains were optimized for the study of low level activity, and were then optimized for each individual, in order to utilize the full range of A/D values for each stored vari able. The system was programmed to sample each chan nel in bursts of 64 points, and to perform a fast Fourier
a bipolar electrode configuration, and inter-electrode spacing was consistent between channels and between subjects (4.8 cm) as limited by the collar to collar dis tance. Although this spacing was larger than usual, it was deemed adequate in order to study global muscle behav ior under the electrode sites, and allowed for the elec trodes to be placed over the muscle groups of interest without recording excessive crosstalk from synergist or antagonist muscles. Two reference electrodes were used, as required by the design of the data recorder. The neck and low back channels used a common reference elec trode at the T7 spinous process, and the shoulder and forearm channels used a common reference at the medial epicondyle of the humerus. Fig. 1demonstrates this elec trode configuration, and the portable data acquisition system. Electrodes were applied a minimum of 10min prior to the initiation of data collection, allowing time for the electrode-tissue impedance to stabilize to an accept able level (Parker and Scott, 1969). The data acquisition system had a pass-band of 10-800Hz, and a sampling rate of 1024Hz per channel, in accordance with the International Society of Electrophysiology and Kinesiol ogy (ISEK) standards on the acquisition of myoelectric signal data (ISEK, 2000). The analog-to-digital conver sion (A/D) was done using an 8 bit fixed point processor, and was programmed in TMS 320 Assembler language. As the resolution of the A/D was not ideal, the channel gains were optimized for the study of low level activity, and were then optimized for each individual, in order to utilize the full range of A/D values for each stored vari able. The system was programmed to sample each chan nel in bursts of 64 points, and to perform a fast Fourier
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