BACKGROUND Skeletal muscle function dysfunction has been reported in patients with cystic fibrosis (CF). Studies so far showed inconclusive data whether reduced exercise capacity is related to intrinsic muscle dysfunction in CF. METHODS Twenty patients with CF and 23 age-matched controls completed an incremental cardiopulmonary cycling test. Further, a Wingate anaerobic test to assess muscle power was performed. In addition, all participants completed an incremental knee-extension test with 31P magnetic resonance spectroscopy to assess muscle metabolism (inorganic phosphate (Pi) and phosphocreatinine (PCr) as well as intracellular pH). In the MRI, muscle cross-sectional area of the M. quadriceps (qCSA) was also measured. A subgroup of 15 participants (5 CF, 10 control) additionally completed a continuous high-intensity, high-frequency knee-extension exercise task during 31P magnetic resonance spectroscopy to assess muscle metabolism. RESULTS Patients with CF showed a reduced exercise capacity in the incremental cardiopulmonary cycling test (VO2peak: CF 77.8 ± 16.2%predicted (36.5 ± 7.4 ml/qCSA/min), control 100.6 ± 18.8%predicted (49.1 ± 11.4 ml/qCSA/min); p < 0.001), and deficits in anaerobic capacity reflected by the Wingate test (peak power: CF 537 ± 180 W, control 727 ± 186 W; mean power: CF 378 ± 127 W, control 486 ± 126 W; power drop CF 12 ± 5 W, control 8 ± 4 W. all: p < 0.001). In the knee-extension task, patients with CF achieved a significantly lower workload (p < 0.05). However, in a linear model analysing maximal work load of the incremental knee-extension task and results of the Wingate test, respectively, only muscle size and height, but not disease status (CF or not) contributed to explaining variance. In line with this finding, no differences were found in muscle metabolism reflected by intracellular pH and the ratio of Pi/PCr at submaximal stages and peak exercise measured through MRI spectroscopy. CONCLUSIONS The lower absolute muscle power in patients with CF compared to controls is exclusively explained by the reduced muscle size in this study. No evidence was found for an intrinsic skeletal muscle dysfunction due to primary alterations of muscle metabolism.

中文翻译：

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囊性纤维化患者的大小调整后的肌肉力量和肌肉代谢与健康对照相同-一项病例对照研究。

背景技术已经报道了患有囊性纤维化（CF）的患者的骨骼肌功能障碍。迄今为止的研究表明，缺乏运动能力是否与CF内在的肌肉功能障碍有关尚无定论。方法20名CF患者和23名年龄匹配的对照者完成了递增的心肺循环测试。此外，进行了Wingate厌氧测试以评估肌肉力量。此外，所有参与者均通过31P磁共振波谱仪完成了膝关节伸直试验，以评估肌肉代谢（无机磷酸盐（Pi）和磷酸肌酐（PCr）以及细胞内pH）。在MRI中，还测量了股四头肌的肌肉横截面积（qCSA）。一个由15名参与者组成的小组（5个CF，10个对照组）另外完成了连续的高强度训练，在31P磁共振波谱中进行高频膝关节伸展运动，以评估肌肉的新陈代谢。结果CF患者在递增的心肺循环测试中显示出运动能力下降（VO2peak：预测的CF 77.8±16.2％（36.5±7.4 ml / qCSA / min），对照的预测的100.6±18.8％（49.1±11.4 ml / qCSA / min ）; p <0.001），以及Wingate测试所反映的无氧能力不足（峰值功率：CF 537±180 W，控制727±186 W;平均功率：CF 378±127 W，控制486±126 W;功率下降CF 12±5 W，控制8±4 W.全部：p <0.001）。在膝关节伸展运动中，CF患者的工作量显着降低（p <0.05）。但是，在线性模型中，分别分析增量膝盖伸展任务的最大工作负荷和Wingate测试的结果，仅分析肌肉的大小和身高，但疾病状况（是否为CF）对解释差异没有帮助。与该发现一致，在细胞内pH和通过MRI光谱法测量的最大运动和峰值运动下，在细胞内pH和Pi / PCr的比率所反映的肌肉代谢中未发现差异。结论本研究中CF的绝对肌肉力量较对照组低，完全可以解释为肌肉尺寸减小。由于肌肉代谢的主要改变，没有发现内在的骨骼肌功能障碍的证据。结论本研究中CF的绝对肌肉力量较对照组低，完全可以解释为肌肉尺寸减小。由于肌肉代谢的主要改变，没有发现内在的骨骼肌功能障碍的证据。结论本研究中CF的绝对肌肉力量较对照组低，完全可以解释为肌肉尺寸减小。由于肌肉代谢的主要改变，没有发现内在的骨骼肌功能障碍的证据。