Relationship Between Foot Muscle Strength And Muscle Morphology In The Elderly

Objective: Foot muscle strength acts important function in human postural control.Foot muscle cross-sectional area and thickness performed good correlation with foot intrinsic muscle strength in young adults.Human muscle mass and strength reduce with aging.To our knowledge,no study was conducted to determine the reliability of test on muscle strength and relationship between foot intrinsic muscle strength and its size in older population.Therefore,the purpose of current study is to assess the reliability of foot muscle strength test,and to evaluate the relationship between foot muscle strength and its size in older population.Methods: A total of 55 participants aged 60-75 were recruited in the study.Portable dynamometer was used to evaluate foot muscle strength at four conditions,named first toe flexion test(FT1),2nd-3rd toe flexion test(FT2-3),2nd-5th toe flexion test(FT2-5)and doming test.Portable musculoskeletal ultrasound device was used to measure the cross-sectional area and thickness of five foot intrinsic muscles,including Flexor Digitorum Brevis(FDB),Abductor Hallucis(Ab H),Flexor Hallucis Brevi(FHB),Quadratus Plantae(QP),and Abductor Digiti Minimi(ABDM).Intra-class correlation coefficients(ICCs)were used to evaluate the reliability of foot intrinsic muscle strength tests in current population.Pearson’s correlation coefficients were used to evaluate the correlation between foot muscle strength and size.Results: All foot muscle strength tests showed excellent Intra-tester reliability(ICC: 0.793-0.920).Meanwhile,good Inter-tester reliability was found in doming test,FT2-3 and FT2-5 tests(ICC: 0.809-0.861).Significant correlation was found FT2-3 test and FDB cross-sectional area(r = 0.359,p = 0.004),QP thickness(r = 0.273,p = 0.033),and QP cross-sectional area(r = 0.287,p = 0.025).FT2-5 test was significantly correlated with QP cross-sectional area(r = 0.319,p = 0.012),QP thickness(r = 0.258,p = 0.045),FDB cross-sectional area(r = 0.297,p = 0.020),and ABDM thickness(r =-0.296,p = 0.020).Conclusions: Finding in current study suggested that toes grip test and doming test are reliable tests to evaluate foot muscle strength in elder population.The grip strength of the lateral foot is significantly correlated with its morphology,but the grip strength of the medial foot muscle and doming force are not correlated with its morphology in elderly.Furthermore,the finding recommends that researchers should cautiously use foot intrinsic muscle size as surrogate on measurement of foot intrinsic muscle function in elders.