Measuring the strength of individual foot muscles is very challenging; however, measuring muscle morphology has been shown to be associated with strength . 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.