超音波エコー強度とMuscle Quality

超音波エコーの強度（輝度）が筋力と心血管機能に関連するという健常高齢男性を対象にした研究を紹介します。

Eduardo Lusa Cadore, et al: Echo intensity is associated with skeletal muscle power and cardiovascular performance in elderly men. Experimental Gerontology, http://dx.doi.org/10.1016/j.exger.2012.04.002 Available online 14 April 2012

超音波エコーで大腿直筋の強度（輝度）と大腿四頭筋の厚さを評価しました。大腿四頭筋筋力と最大酸素摂取量なども評価して、これらの関連を調査しました。その結果、超音波エコーの強度（輝度）と筋力・心血管機能に有意な負の相関を認めました。筋力と心血管機能には有意な正の相関を認めました。

これより超音波エコーの強度（輝度）でMuscle Quality（筋肉の質）を容易に評価できる可能性があるという結論です。強度（輝度）変化の原因として、筋肉内の脂肪浸潤や結合組織の量の違いが考えられています。

超音波エコーはサルコペニアの診断時、筋肉量の評価に有用と考えていました。しかし、筋肉量だけでなくMuscle Quality（筋肉の質）も強度（輝度）で評価できるとなると、より有用な検査機器となりますね。コストや簡便性を考えると他の検査機器より優れているかもしれません。

Abstract

The purpose of the present study was to investigate the relationship between echo intensity, neuromuscular and cardiorespiratory performance in elderly. Third-one healthy elderly men (65.5 ± 5.0) participated in this study. Echo intensity of rectus femoris and quadriceps femoris muscle thickness were determined by ultrasound images. Lower-body isometric and isokinetic peak torque (60, 180 and 360°^.s-1), as well as rate of force development were evaluated as strength parameters. In addition, torque per unit of muscle mass was evaluated by the quotient between isometric peak torque of the knee extensors and the quadriceps femoris muscle thickness. The peak oxygen uptake (VO_2peak), maximum aerobic workload (W_máx), absolute (VT₁ and VT₂) ventilatory thresholds, as well as workloads at VT₁ and VT₂ (W_VT1 and W_VT2) were evaluated during a maximal incremental test on a cycle ergometer. There were significant negative correlations between the individual values of echo intensity with the corresponding individual values of isometric and isokinetic peak torque (60, 180 and 360°^.s-1) (r = − 0.48 to r = − 0.64; P < 0.05), as well as with W_VT1 (r = − 0.46) and W_VT2 (r = − 0.50) (P < 0.05). In addition, significant positive correlations were observed between torque per unit of muscle mass and cardiovascular parameters (r = 0.52 to r = 0.60; P < 0.001). The present results suggests that the echo intensity analysis using computer-aided gray-scale analysis is a low cost, easily accessible, and safe method to evaluate the muscle quality, and may contribute to the research of neuromuscular and cardiovascular performance in elderly.