Measuring the strength of individual foot muscles is very challenging; however, measuring muscle morphology has been shown to be associated with strength [1]. A reliable method of assessing foot muscle atrophy and hypertrophy would therefore be beneficial to researchers and clinicians. Real-time ultrasound (US) is a non-invasive, objective and inexpensive method of assessing muscle morphology and has been employed widely to quantify cross-sectional area (CSA) and linear dimensions of larger muscles (e.g. quadriceps, triceps surae). Few studies, however, have determined its ability to measure the small muscles of the foot and ankle. This study aimed to determine whether US is a reliable tool to measure the morphology of the toe flexor muscles.

The method was found to have good reliability (ICC=0.83-0.99) with LoA between 7.9-29.1% of the relative muscle size. Although published data is not available for all muscles tested, the LoA were within the ranges that we may expect for changes in muscle size due to ageing, disease or intervention. Ultrasound is therefore deemed a reliable method to measure morphology of the toe flexor muscles.