RESUMEN
BACKGROUND: Simple and reliable methods to evaluate muscle mass in older people are lacking. AIM: To evaluate ultrasound as a measure of RF muscle mass and quality in healthy subjects of different ages and gender, assessing its concordance with dual energy X-ray densitometry (DEXA) and association with muscle strength and walking capacity. METHODS: We selected 54 adults of both genders, aged 20-55 years and 51 adults older than 60 years. Ultrasound images of the RF were obtained at the mid-thigh to measure its thickness and ultrasonographic density using a GE Logiq e equipment. Body composition was assessed by DEXA. Quadriceps isometric strength and 12 minutes' walk were also measured and gender specific t scores for older adults were calculated using the values obtained in adults. RESULTS: RF ultrasound measurements correlated significantly with lean body mass assessed by DEXA (Double energy X-ray absorptiometry). The concordance between both measures was also adequate. Older people had lower muscle mass and worse ultrasound parameters than adults. Older males with a t score for quadriceps strength of -2 or less, had a significantly higher RF grayscale density. Older males with a 12 minutes' walk t score of -2 or less and old males and females with a walking speed of 1m/s or less had a lower RF thickness. DISCUSSION: There is a good concordance between RF ultrasound and DEXA. CONCLUSIONS: Assessment of RF using ultrasound appears to be a reliable and accurate method to evaluate muscle mass in older people.