Measuring and managing foot muscle weakness

Abstract

Foot muscle weakness is caused by disease, injury, inactivity and ageing, with disabling consequences. Exercise improves muscle weakness however, adherence to correct technique is challenging. Biofeedback may improve performance. Chapter One reviews the literature on small foot muscles, muscle function, measurement, causes and consequences of foot muscle weakness, and the role of exercise. Chapter Two is a systematic review on the relationship between foot pain, muscle strength and size. Eight studies were identified evaluating the relationship between foot pain and foot muscle strength or size, with a significant association between foot pain and muscle weakness when pain is of high intensity and weakness measured by toe flexion force. Chapter Three is a reliability study assessing size of abductor hallucis and medial belly flexor hallucis brevis muscles by ultrasound in 21 adults and identify their relationship with toe strength, foot morphology, balance. Intra-rater reliability was excellent. Significant associations were found between cross-sectional area of abductor hallucis with great toe flexion force, arch height sit and stand, truncated and full foot length, balance. Significant associations found between cross-sectional area of medial belly flexor hallucis brevis with Foot Posture Index, truncated and full foot length. After controlling for body size, cross-sectional area of abductor hallucis remained a significant correlate of great toe flexor strength. Chapter Four describes the development of the Archie biofeedback device. Device feasibility is evaluated in Chapter Five by repeat testing of 30 adults performing four foot exercises using Archie, with 89% of exercise and foot location variables collected consistently. Biofeedback significantly improved foot location for all exercises and 97% of participants reported biofeedback helped exercise performance. Archie appears to be a safe and feasible biofeedback device to assist participants perform exercise.