Reliability analyses and values of isometric shoulder flexion and trunk extension strengths stratified by body mass index.
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The main goal of this study was to investigate the reliability of muscle strength across different levels of obesity. A sample of 142 healthy subjects performed maximum voluntary isometric contractions for shoulder flexion and trunk extension on each of four days. Subjects were recruited into one of three groups, non-obese, overweight, or obese, based on body mass index (BMI). Reliability of the strength measurements within each session and across the four sessions was determined from the intraclass correlation coefficient, coefficient of repeatability, coefficient of variation, and standard error of measurement. For the shoulder flexion measures, the coefficient of variation was < 10% and intraclass correlation coefficient was > 0.75. The absolute reliability of trunk extension strength measurement was rejected due to a high variability across sessions. For both tasks, comparable strengths across the BMI groups were found.