This study investigated the validity and reliability of fixed strain gauge measurements of isometric quadriceps force in patients with chronic obstructive pulmonary disease (COPD). A total cohort of 138 patients with COPD were assessed. To determine validity, maximal volitional quadriceps force was evaluated during isometric maximal voluntary contraction (MVC) manoeuvre via a fixed strain gauge dynamometer and compared to (a) potentiated non-volitional quadriceps force obtained via magnetic stimulation of the femoral nerve (twitch (Tw); n = 92) and (b) volitional computerized dynamometry (Biodex; n = 46) and analysed via correlation coefficients. Test–retest and absolute reliability were determined via calculations of intra-class correlation coefficients (ICCs), smallest real differences (SRDs) and standard errors of measurement (SEMs). For this, MVC recordings in each device were performed across two test sessions separated by a period of 7 days (n = 46). Strain gauge measures of MVC demonstrated very large correlation with Tw and Biodex results (r = 0.86 and 0.88, respectively, both p < 0.0001). ICC, SEM and SRD were numerically comparable between strain gauge and Biodex devices (ICC = 0.96 vs. 0.93; SEM = 8.50 vs. 10.54 N·m and SRD = 23.59 vs. 29.22 N·m, respectively). The results support that strain gauge measures of quadriceps force are valid and reliable in patients with COPD.
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机译：本研究调查了固定应变片测量的等长四头肌力量在慢性阻塞性肺疾病（COPD）患者中的有效性和可靠性。评估了总共138名COPD患者。为了确定有效性，在等距最大自愿收缩（MVC）操纵期间，通过固定应变计测力计评估了最大自愿股四头肌力量，并将其与（a）磁刺激股神经（抽搐（Tw））得到的增强的非自愿股四头肌力量进行比较； n = 92）和（b）自愿计算机测功（Biodex; n = 46），并通过相关系数进行分析。重测和绝对可靠性是通过计算组内相关系数（ICC），最小实差（SRD）和测量标准误差（SEM）来确定的。为此，每个设备中的MVC记录是在两个测试会话之间执行的，间隔为7天（n = 46）。 MVC的应变仪测量结果显示与Tw和Biodex结果非常相关（r分别为0.86和0.88，均p <0.0001）。在应变仪和Biodex设备之间，ICC，SEM和SRD在数值上可比（ICC = 0.96 vs. 0.93； SEM = 8.50 vs. 10.54 N·m，SRD = 23.59 vs. 29.22 N·m）。结果支持应变计测量股四头肌的力量在COPD患者中是有效和可靠的。
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