Magnetic resonance imaging (MRI) is the gold standard for measuring muscle size. However, postural conditions for thigh musculature have not been standardized across studies, with some employing supine or prone positions and the thigh either placed on the examination table or suspended to avoid contact. In either case, the thigh is compressed or sagged by gravity, potentially affecting muscle size. This study aimed to examine the effects of postural conditions on thigh muscle size. Twenty Olympic‐style weightlifters and 20 untrained controls (10 men and 10 women in each group) underwent 3‐Tesla MRI in the supine and prone positions, with the thigh in compressed and suspended conditions to determine the maximal anatomical cross‐sectional area (ACSAmax) and muscle volume of 15 thigh muscle groups/individual muscles. Postural conditions changed the ACSAmax of the quadriceps (range of postural‐related changes: 1.0%–7.9%), hamstrings (0.8%–19.1%), and adductors (2.4%–19.2%). Regardless of measurement position, the total volume of thigh muscles decreased under compressed conditions (0.6%–3.8%). Quadriceps and adductors decreased in muscle volume under compressed conditions (0.9%–4.0% and 0.8%–6.6%), while hamstrings increased (1.4%–9.3%). Male weightlifters, who possessed the largest thigh muscle volume, showed greater postural‐related changes in the muscle volume of quadriceps, hamstrings, and adductors than the other subgroups. Therefore, postural conditions during MRI substantially change thigh muscle size, and the magnitude of the change depends on muscle size. Our results provide in vivo evidence of the compressive behavior of thigh muscles and a new technical perspective for assessing thigh muscle size.

中文翻译：

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磁共振成像期间姿势条件对大腿肌肉大小的影响


磁共振成像 （MRI） 是测量肌肉大小的黄金标准。然而，大腿肌肉组织的姿势条件在研究中尚未标准化，一些研究采用仰卧或俯卧姿势，大腿要么放在检查台上，要么悬空以避免接触。在任何一种情况下，大腿都会因重力而受到压迫或下垂，从而可能影响肌肉大小。本研究旨在检查姿势条件对大腿肌肉大小的影响。20 名奥林匹克式举重运动员和 20 名未经训练的对照组（每组 10 名男性和 10 名女性）在仰卧位和俯卧位接受了 3-特斯拉 MRI，大腿处于压缩和悬吊状态，以确定最大解剖横截面积 （ACSAmax） 和 15 个大腿肌肉群/单个肌肉的肌肉体积。姿势条件改变了股四头肌 （姿势相关变化的范围： 1.0%–7.9%） 、腘绳肌 （0.8%–19.1%） 和内收肌 （2.4%–19.2%） 的 ACSAmax。无论测量位置如何，在压缩条件下大腿肌肉的总体积都会减少 （0.6%–3.8%）。在压缩条件下，股四头肌和内收肌的肌肉体积减少 （0.9%–4.0% 和 0.8%–6.6%），而腘绳肌增加 （1.4%–9.3%）。拥有最大大腿肌肉体积的男性举重运动员表现出比其他亚组更大的股四头肌、腘绳肌和内收肌肌肉体积的姿势相关变化。因此，MRI 期间的姿势状况会显著改变大腿肌肉的大小，而变化的程度取决于肌肉大小。我们的结果为大腿肌肉的压缩行为提供了体内证据，并为评估大腿肌肉大小提供了新的技术视角。