Functional assessments of foot strength: a comparative and repeatability study

Abstract

BackgroundEvaluating the strength of the small muscles of the foot may be useful in a variety of clinical applications but is challenging from a methodology standpoint. Previous efforts have focused primarily on the functional movement of toe flexion, but clear methodology guidelines are lacking. A novel foot doming test has also been proposed, but not fully evaluated. The purposes of the present study were to assess the repeatability and comparability of several functional foot strength assessment techniques.MethodsForty healthy volunteers were evaluated across two testing days, with a two-week doming motion practice period between them. Seven different measurements were taken using a custom toe flexion dynamometer (seated), custom doming dynamometer (standing), and a pressure mat (standing). Measurements from the doming dynamometer were evaluated for reliability (ICCs) and a learning effect (paired t-tests), while measurements from the toe flexion dynamometer and pressure mat were evaluated for reliability and comparability (correlations). Electromyography was also used to descriptively assess the extent of muscle isolation in all measurements.ResultsDoming showed excellent within-session reliability (ICCs > 0.944), but a clear learning effect was present, with strength (p < 0.001) and muscle activity increasing between sessions. Both intrinsic and extrinsic muscles were engaged during this test. All toe flexion tests also showed excellent reliability (ICCs > 0.945). Seated toe flexion tests using the dynamometer were moderately correlated to standing toe flexion tests on a pressure mat (r > 0.54); however, there were some differences in muscle activity. The former may better isolate the toe flexors, while the latter appeared to be more functional for many pathologies. On the pressure mat, reciprocal motion appeared to display slightly greater forces and reliability than isolated toe flexion.ConclusionsThis study further refines potential methodology for foot strength testing. These devices and protocols can be duplicated in the clinic to evaluate and monitor rehabilitation progress in clinical populations associated with foot muscle weakness.

Early-Stage Diabetic Neuropathy Reduces Foot Strength and Intrinsic but Not Extrinsic Foot Muscle Size

“…A doming test (DOM) was used to evaluate the muscles controlling the medial longitudinal arch (MLA) while a toe flexion test was used to simultaneously evaluate great toe flexion (GTF) and lateral toe flexion (LTF) strengths. All tests were performed based on previously published methodology [31,34,35]. Briefly, the DOM was performed on a custom-built apparatus.…”

“…The strength of the smaller foot muscles has not been evaluated. A few previous studies by our group and others have proposed functional strength testing protocols for evaluating distal foot strength [31][32][33][34][35], but these have not yet been applied to DPN. Foot strength testing in combination with US imaging may provide insight into the manner in which DPN affects atrophy and weakness [12].…”

Auswirkungen des Trainings der intrinsischen Fußmuskulatur bei Patienten*innen mit Sprunggelenkinstabilität – ein narrativer Review

“…Es ist anzumerken, dass ein Training der intrinsischen Fußmuskulatur nicht isoliert möglich ist. Untersuchungen zeigten zwar beispielsweise eine starke Muskelaktivität des M. abductor hallucis während der SFE, jedoch konnte dabei auch eine erhöhte Aktivität der Fibularisgruppe und des M. tibialis anterior nachgewiesen werden [30]. Diese Ergebnisse verdeutlichen das synergistische Zusammenwirken der extrinsischen und intrinsischen Muskulatur als Stabilisatoren der Fußgewölbe sowie der Sprunggelenke.…”

“…Zum einen ist dies ein weiteres Argument für ein Training der intrinsischen Fußmuskulatur, da hierüber die funktionelle Kette der unteren Extremität aktiviert wird. Zum anderen sollte jedoch beachtet werden, dass die extrinsische Muskulatur möglicherweise schwache, intrinsische Muskeln überkompensieren könnte [30].…”

Fat Is Consistently Present within the Plantar Muscular Space of the Human Foot—An Anatomical Study

“…The active, passive and neural subsystems form the components of the foot core system (FCS) and contribute to maintaining foot function [1]. The foot's intrinsic muscles are gaining increasing attention in injury prevention [2][3][4], as well as for musculoskeletal assessment [5,6] and rehabilitation [3,7,8] of lower limb disorders.…”