Neuromuscular Plasticity Laboratory, Institute of Exercise Physiology and Rehabilitation Science, University of Central Florida, Orlando, Florida, United States of America.
Applied Neuromuscular Physiology Laboratory, Oklahoma State University, Stillwater, Oklahoma, United States of America.
PLoS One. 2022 Jan 11;17(1):e0262553. doi: 10.1371/journal.pone.0262553. eCollection 2022.
Echo intensity (EI) is a novel tool for assessing muscle quality. EI has traditionally been reported as the mean of the pixel histogram, with 0 and 255 arbitrary units (A.U.) representing excellent and poor muscle quality, respectively. Recent work conducted in youth and younger and older adults suggested that analyzing specific EI bands, rather than the mean, may provide unique insights into the effectiveness of exercise and rehabilitation interventions. As our previous work showed deterioration of muscle quality after knee joint immobilization, we sought to investigate whether the increase in EI following disuse was limited to specific EI bands. Thirteen females (age = 21 yrs) underwent two weeks of left knee immobilization and ambulated via crutches. B-mode ultrasonography was utilized to obtain images of the immobilized vastus lateralis. The percentage of the total number of pixels within bands of 0-50, 51-100, 101-150, 151-200, and 201-255 A.U. was examined before and after immobilization. We also sought to determine if further subdividing the histogram into 25 A.U. bands (i.e., 0-25, 26-50, etc.) would be a more sensitive methodological approach. Immobilization resulted in a decrease in the percentage of pixels within the 0-50 A.U. band (-3.11 ± 3.98%), but an increase in the 101-150 A.U. (2.94 ± 2.64%) and 151-200 A.U. (0.93 ± 1.42%) bands. Analyses of variance on the change scores indicated that these differences were large and significant (%EI0-50 vs. %EI101-150: p < .001, d = 1.243); %EI0-50 vs. %EI151-200: p = .043, d = 0.831). The effect size for the %EI51-100 versus %EI101-150 comparison was medium/large (d = 0.762), but not statistically significant (p = .085). Further analysis of the 25 A.U. bands indicated that the percentage of pixels within the 25-50 A.U. band decreased (-2.97 ± 3.64%), whereas the 101-125 (1.62 ± 1.47%) and 126-150 A.U. (1.18 ± 1.07%) bands increased. Comparison of the 50 A.U. and 25 A.U. band methods found that 25 A.U. bands offer little additional insight. Though studies are needed to ascertain the factors that may influence specific bands, changes in EI during muscle disuse are not homogeneous across the pixel histogram. We encourage investigators to think critically about the robustness of data obtained from EI histograms, rather than simply reporting the EImean value, in muscle quality research.
回声强度（EI）是一种评估肌肉质量的新工具。EI 传统上被报告为像素直方图的平均值，其中 0 和 255 任意单位（A.U.）分别代表优秀和较差的肌肉质量。最近在年轻人和较年轻及老年人中进行的研究表明，分析特定的 EI 波段，而不是平均值，可能会提供有关运动和康复干预效果的独特见解。由于我们之前的工作表明膝关节固定后肌肉质量恶化，我们试图研究在失用后 EI 的增加是否仅限于特定的 EI 波段。13 名女性（年龄=21 岁）接受了两周的左膝关节固定，并通过拐杖步行。B 型超声用于获得固定股外侧肌的图像。在固定前后检查了 0-50、51-100、101-150、151-200 和 201-255 A.U. 内像素总数的百分比。我们还试图确定将直方图进一步细分为 25 A.U. 波段（即 0-25、26-50 等）是否是一种更敏感的方法。固定导致 0-50 A.U. 波段内的像素百分比下降（-3.11±3.98%），但 101-150 A.U.（2.94±2.64%）和 151-200 A.U.（0.93±1.42%）波段增加。对变化分数的方差分析表明，这些差异很大且显著（%EI0-50 与 %EI101-150：p<.001，d=1.243）；%EI0-50 与 %EI151-200：p=0.043，d=0.831）。%EI51-100 与 %EI101-150 比较的效应大小为中/大（d=0.762），但无统计学意义（p=0.085）。对 25 A.U. 波段的进一步分析表明，25-50 A.U. 波段内的像素百分比下降（-2.97±3.64%），而 101-125（1.62±1.47%）和 126-150 A.U.（1.18±1.07%）波段增加。比较 50 A.U. 和 25 A.U. 波段方法发现，25 A.U. 波段提供的见解很少。尽管需要进一步研究确定可能影响特定波段的因素，但肌肉失用期间 EI 的变化并非在像素直方图中均匀分布。我们鼓励研究人员批判性地思考从 EI 直方图中获得的数据的稳健性，而不是简单地报告 EImean 值，在肌肉质量研究中。
