Difference Between Starting Foot Exercise with Intrinsic and Extrinsic Muscles on Selected Foot ‎Muscle Morphology

Flat foot deformity is one of the most prevalent musculoskeletal malalignments among adolescents. It is not obvious whether starting the exercises on each of the muscles of intrinsic or extrinsic has an effect on the morphologic characteristics of the other muscle groups or not. Hence, the purpose of this study was to compare the effects of starting flat foot corrective exercises with intrinsic or extrinsic exercises on the morphologic characteristics of the Abductor hallucis and tibialis posterior muscles in adolescents afflicted by flat foot deformity.

Twenty-five boy adolescent were randomly divided into intrinsic (n=10, 10.8±0.78 years, 138.8. ±7.22cm, 40.7±9.49 kg) and extrinsic (n=12, 11±0.85 years, 143.1±6.14 cm, 42.25±9.05kg) groups (three boy left the study). For the 6 weeks, the intrinsic group performed intrinsic exercises and the extrinsic group performed extrinsic exercises. After 6 weeks the muscle thickness and cross-section area of abductor hallucis (the selected muscles for intrinsic group) and tibialis posterior (the selected muscles for extrinsic group) muscles were measured by ultrasound system. For measuring the flat foot navicular drop test was used and included criteria was score more than 0.8 in dominant foot. Kolmogorov-Smirnov fitness test and Repeated Measures ANOVA were used to analyze the data. A level of P≤0.05 was considered significant.

The data shows that starting the corrective program with extrinsic exercises has destructive effects on the intrinsic foot muscle morphology. In the extrinsic group, interaction effect was significant (p=0.034) that means extrinsic exercises has disadvantage effect on abductor hallucic thickness.

as can be seen, probably starting flat foot exercises with extrinsic muscle can decrease thickness and cross section area of intrinsic foot muscle namely abductor hallucic. These effect can be result from neurophysiological principle of muscle recruitment. So it is better to start flat foot corrective exercises deformity with intrinsic foot muscle activation and strengthening and after up-regulation of intrinsic muscles, add extrinsic exercises to them.