Cross-sectional Areas Of Selected Foot Muscles Following An 8-week Footwear Transition Program In People With Plantar Fasciitis

Plantar fasciitis (PF), a common painful foot condition, is often treated with inserts and supportive shoes. This can lead to muscle atrophy and high recurrence rates. Transitioning to minimal shoes may strengthen foot muscles, reduce plantar fascia strain and prevent the recurrence of PF. PURPOSE: To compare changes in intrinsic foot muscle size from baseline to post-8-week footwear transition (minimal shoe (MS) and conventional shoe (CON)) in individuals with PF. METHODS: This is an ongoing clinical trial where 41 (of 120) individuals (52.33 ± 7.70 yrs., 39F/2M, 23 MS, 18 CON) with PF have completed their 8-week footwear transition, including a slow progression to their normal daily step count. The cross-sectional areas (CSA) of 4 intrinsic and 3 extrinsic muscles (see Table below) were measured by digitization of ultrasound images by a blinded assessor. These CSAs were compared between the MS and CON groups at baseline and post-transition. Given the preliminary nature of these data, relative changes (%) and effect sizes (ES) were used for comparison. RESULTS: While the % changes and ES are small, the majority of the muscles increased in size in the MS group. These increases are smaller than those that have been reported with MS use in healthy individuals. This is likely due to the injured state of the foot and lower daily step counts in this PF group compared to other studies. The majority of muscles in the CON group decreased in size which is consistent with previous reports of muscle weakening when support is added to the foot. CONCLUSION: These preliminary data suggest that MS may promote foot muscle strengthening while adding support to the foot may promote muscle weakening in those with PF. This will be further examined at the 3-month post-transition follow-up and within a larger sample as the study proceeds. Research reported in this abstract was supported by the National Institute for Aging of the National Institutes of Health under award number R01AG071646. - MINIMAL SHOES CONVENTIONAL SHOES Baseline 3 Months Follow-Up Changes % Effect size Baseline 3 Months Follow-Up Changes % Effect size Abductor hallucis brevis 1.85±0.47 1.88±0.48 +1% .06 1.81±0.49 1.75±0.59 -%4 .11 Flexor digitorum Brevis 1.59±0.30 1.59±0.33 0% .01 1.52±0.26 1.60±0.31 +%5 .28 Quadratus Plantae 1.09±0.30 1.13±0.38 +3% .11 1.05±0.30 0.89±0.31 -%17 .53 Abductor Digiti Minimi 0.67±0.28 0.69±0.25 +3% .07 0.70±0.41 0.69±0.25 -%2 .03 Tibialis Posterior 3.85±1.03 4.16±1.24 +8% .27 3.27±0.63 3.25±0.62 -%1 .03 Flexor Hallucis Longus 2.15±0.64 2.17±0.89 +1% .03 2.49±0.84 2.33±0.88 -%7 .18 Flexor Digitorum Longus 1.27±0.47 1.39±0.67 +9% .21 1.34±0.38 1.28±0.37 -%4 .16 Supported by: Research reported in this abstract was supported by the National Institute for Aging of the National Institutes of Health under award number R01AG071646.