A comparison of lower limb muscle activation pattern using voluntary response index between pronated and normal foot structures during forward jump landing

Publication date: Available online 21 July 2017
Source:Journal of Bodywork and Movement Therapies
Author(s): Hosein Kouhzad Mohammadi, Mohammad Mehravar, Khosro Khademi Kalantari, Sedighe Sadat Naimi, Alireza Akbarzadeh Baghban, Farshad Okhovatian, Asghar rezasoltani, Mohammad Ali Mohseni Bandpei, Navid Taheri
BackgroundPronated foot is one of the important factors contributing to the musculoskeletal problems of the lower extremities. It is known that in pronated foot, excessive mechanical load is applied to the lower limb structures which may result in altered biomechanics and muscle activation patterns. The aim of this study was to determine changes in the muscle activation pattern of the lower extremities in the pronated compared to normal foot individuals, using the voluntary response index (VRI).MethodsIn this cross sectional study, 15 asymptomatic pronated foot individuals (mean age 23.27 ± 3.28 years) and 15 normal subjects (mean age 23.40 ± 3.11 years) were recruited by simple non-random sampling. Electrical activities of gluteus medius (GM), vastus lateralis (VL), vastus medialis (VM), biceps femoris, semitendinosus (ST), and medial gastrocnemius (MG) muscles were recorded during a forward jump landing task. Voluntary response index (VRI) variables, included similarity index (SI) and magnitude (Mag) were also evaluated.ResultsMuscle activity of VM (p < 0.001) and ST (p = 0.010) were significantly higher but VL (p = 0.039) and MG (p = 0.001) were significantly lower in pronated foot, compared to normal subjects. Similarity index was found to be different (p < 0.001) between pronated foot and healthy individuals. No significant difference was found in terms of Mag between the two groups (p = 0.576).ConclusionThe altered pattern of lower limb muscle activation identified in the pronated foot during landing may be attributed to the different activation in VL, VM, MG and ST muscles. Adaptations to the biomechanical effects due to the pronated foot causing altered activation of VL, VM, MG, and ST muscles, resulting in an altered pattern of muscle activation. This change in activation pattern may harm the effectiveness of movement control processes; and might also predispose individuals with pronated foot to injuries. It seems that an altered motor strategy with the aim of minimizing biomechanical changes, predisposes individuals to injuries. However, further large scale studies are needed to support the findings of the present study.



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