Anterior thigh composition measured using ultrasound imaging to quantify relative thickness of muscle and non-contractile tissue: a potential biomarker for musculoskeletal health.

This study aimed to use ultrasound imaging to provide objective data on the effects of ageing and gender on relative thickness of quadriceps muscle and non-contractile tissue thickness (subcutaneous fat, SF, combined with perimuscular fascia). In 136 healthy males and females (aged 18-90 years n = 63 aged 18-35 years; n = 73 aged 65-90) images of the anterior thigh (dominant) were taken in relaxed supine using B-mode ultrasound imaging. Thickness of muscle, SF and perimuscular fascia were measured, and percentage thickness of total anterior thigh thickness calculated. Independent t-tests compared groups. Correlation between tissue thickness and BMI was examined using Pearson's coefficient. Muscle thickness was: 39  ±  8 mm in young males, 29  ±  6 mm in females, 25  ±  4 mm in older males and 20  ±  5 mm in females. Percentage muscle to thigh thickness was greater in young participants (p = 0.001). Percentage SF and fascia was 17  ±  6% in young and 26  ±  8% in older males, 32  ±  7% in young and 44  ±  7% in older females. BMI was similar for age and correlated moderately with non-contractile tissue (r = 0.54; p < 0.001) and poorly with muscle (r = -0.01; p = 0.93). In conclusion, this novel application of ultrasound imaging as a simple and rapid means of assessing thigh composition (relative thickness of muscle and non-contractile tissue) may help inform health status, e.g. in older people at risk of frailty and loss of mobility, and aid monitoring effects of weight loss or gain, deconditioning and exercise.