Background The knee adduction moment (KAM) during gait was reported to affect knee osteoarthritis (OA) , and therefore a gait style with decreased KAM is thought to be one way to prevent knee OA . The Nanba style walk (N-walk) is a walking style with the step of the leg and swing of the arm at the same time as small trunk rotation , and the body's center of gravity is directly moved close to the center of the pressure. This gait modification is assumed to decrease the lever arm of the KAM, so that the KAM would be decreased due to the N-walk.
Objectives The purpose of the study was to investigate the effect of the Nanba walk on KAM during gait in healthy adults as a preliminary study.
Methods 28 healthy adults consisting of 16 men and 12 women (21.7 ± 0.4 years old) participated. All participants including those in the pilot study were informed as to the nature of the study, and their informed consent was obtained as approved by the Ethics Committee of Seijoh University. A three-dimensional analysis system (Venus 3D; Nobby Tech, Tokyo, Japan) with a 10-camera and a force plate (AccuGait; AMTI, MA, USA) were used to obtain the kinematics and kinetic data by inverse dynamic methods and global optimization. KAMs were normalized to body mass and leg length (no unit). The 1st and 2nd peak KAMs during stance phase and the lever arm length of the KAM (frontal plane) at both peak KAMs were measured to compare with free gait and N-walk. N-walk gait speed was controlled within ± 5% of a free gait. Subjects were asked to walk along a 6-m walkway, and three successful trials were recorded. Average data were used in final analysis. The EMG of the gluteus medius muscle, which was reported to relate to KAM , was measured, and Integral EMGs (iEMG) of the first and second half of the stance phase after full-wave EMG rectification were used to compare the two gait styles.
Results The peak 1st and 2nd KAM of N-walk (4.9 ± 1.2 ×10–2 and 4.7 ± 1.5 ×10-2) were significantly decreased compared to the KAMs of free gait (5.6 ± 1.1 ×10–2 and 5.6 ± 1.6 ×10–2). The lever arm length at the peak 1st and 2nd KAM of N-walk (3.7 ± 1.1 and 3.3 ± 1.0 cm) were also significantly decreased compared to the lever arm length of free gait (3.9 ± 1.0 and 4.1 ± 1.0 cm). The iEMGs of gluteus medius muscle of the first and second half of the N-walk (2.8 ± 1.3 and 3.0 ± 1.4 Vs) were significantly increased compared to the iEMGs of the free gait (1.9 ± 0.9 and 2.1 ± 1.0 Vs, p<0.05).
Conclusions The 1st and 2nd peak of KAM with N-walk were significantly decreased compared to the KAMs of free gait due to the lever arm length of KAMs with increased gluteus medius muscle activity. N-walk is one of the traditional Japanese walking styles when wearing a kimono. This gait modification is assumed to one of the indications of a walking style to help prevent medial knee osteoarthritis.
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Acknowledgement This work was supported by JSPS KAKENHI Grant Number 15K12613.
Disclosure of Interest None declared