Reproducibility of computer measurement of maximal isometric strength and electromyography in sedentary middle-aged women.

The objectives of this study were (i) to determine the reproducibility of computer measurements of isometric strength and related electromyography in several muscle groups in sedentary middle-aged women, (ii) to evaluate the effects of different digital signal averaging methods on the reproducibility, (iii) to determine the final test score to be preferred in terms of improved reproducibility of isometric strength measurements, and (iv) to evaluate potential advantages provided by the computer measurement. Fifteen subjects were measured three times within a 2-week period. The measurements consisted of recordings of maximal isometric strength and rate of force production during trunk extension and flexion, leg extension and dominant forearm flexion with simultaneous recordings of surface electromyography, except in the trunk flexors. The following four final test scores were determined for each trial: the maximum of the three scores, the mean of the two highest scores, the median of the three scores and the mean of the three scores. The scores for the strength measurement were generally more reproducible (coefficient of variation, CV, approximately 6% and intraclass correlation coefficient ICCC, approximately 0.90) than those of the other measurements (CV > 10%, ICCC 0.13-0.97). There was no obvious preference for any type of final test score or for the width of the averaging window in the computer analysis. For isometric strength the reproducibility of the computer measurements was comparable to that of the voltmeter assessments. Computer analysis seems to be a versatile method for determining parameters of neuromuscular performance with reasonable reproducibility.