Madsen O R, Brot C
Department of Rheumatology, Copenhagen Municipal Hospital, Denmark.
Clin Rheumatol. 1996 Mar;15(2):154-60. doi: 10.1007/BF02230333.
The intra-session and inter-session reproducibility of knee extensor and flexor strength measurements were examined in 21 gonarthrotic subjects (ten women and eleven men). Using the Cybex 6000 dynamometer, isokinetic peak torque and total work at 30 and 120 degrees/second and isometric peak torque were measured three times on separate days within two weeks by the same examiner. The reproducibility of walking and stair climbing time measurements was also assessed. The concept of critical difference (i.e. the difference between two measurements which would be statistically significant when applied to a reference group in steady state) for the interpretation of muscle strength data obtained by monitoring individual patients is presented. Individual coefficients of variation (CV) were calculated for each muscle strength variable. Depending on the velocity and on whether peak torque or total work were measured, the median CV of intra-session and inter-session extensor strength measurements ranged from 1.5-4.9% and 7.4-10.1%, respectively. CVs for flexor strength measurements were significantly higher. Substantial variability of within subject variances were found, e.g. the 80% central range of CVs for extensor torque at 30 degrees/second was 2.5-29.5% (inter-session). Calculated from CVs, critical differences for inter-session measurements exceeded 30% for all muscle strength variables. Median CVs for walking and stair-climbing time were 7.0% and 4.9%, respectively. In conclusion, the large CVs and corresponding critical differences may be a major limitation in the use of muscle strength measurements in the individual gonarthrotic patient.
在21名膝关节病患者（10名女性和11名男性）中检查了膝关节伸肌和屈肌力量测量的组内和组间重复性。使用Cybex 6000测力计，由同一名检查者在两周内的不同日期对30度/秒和120度/秒时的等速峰值扭矩、总功以及等长峰值扭矩进行了三次测量。还评估了步行和爬楼梯时间测量的重复性。提出了用于解释通过监测个体患者获得的肌肉力量数据的临界差异概念（即当应用于稳态参考组时具有统计学意义的两次测量之间的差异）。计算了每个肌肉力量变量的个体变异系数（CV）。根据速度以及测量的是峰值扭矩还是总功，组内和组间伸肌力量测量的CV中位数分别为1.5%-4.9%和7.4%-10.1%。屈肌力量测量的CV显著更高。发现受试者内方差存在很大变异性，例如，30度/秒时伸肌扭矩的CV的80%中心范围为2.5%-29.5%（组间）。根据CV计算，所有肌肉力量变量的组间测量临界差异超过30%。步行和爬楼梯时间的CV中位数分别为7.0%和4.9%。总之，大的CV和相应的临界差异可能是个体膝关节病患者使用肌肉力量测量的主要限制。
