What is their drive? Armswing in human walking

Abstract

Fig. 1. Mean resultant errors in HJC location between the Harrington and Davis method in the transverse plane. The error bars indicate ± one standard deviation. single group only. Gait data were collected using the modified Helen Hayes marker set. HJCs were generated according to the Davis and Harrington equations. The difference in hip joint centres between these methods was calculated in the pelvic coordinate system for each subject, using the x lateral, y anterior, z superior positions of the HJCs. Paired t-tests were used to compare the co-ordinates for each method. Finally, hip and knee angles in all three planes were calculated and compared using the different HJC methods. Results: Fig. 1 shows the mean difference in the transverse (xy) plane for the position of the HJC calculated by the Harrington equation, compared to the Davis equation for each group. All differences in x, y and z (not shown in figure) were statically significant except for the BMI and SS group in the x direction. Short stature was shown to be most affected by the Harrington calculation, with the HJC placed an average of 26 mm (±5 mm) posterior to the Davis HJC. Calculation of the average difference in joint angles throughout the gait cycle showed the largest variation in the SS group: For example, in the sagittal plane, a mean 8 ◦ difference in knee flexion was calculated for this group, compared to 1 ◦ for the normal group. Discussion and conclusions: For the normal adult group results from this study are comparative to those carried out previously [3]. For the new populations studied here, the differences in HJC location were even greater, with an associated change in the kinematic data. In at least one case of a patient with small stature, the thigh rotation was deemed as within the normal bands compared to the Davis method, but outside of normal according to the Harrington method. Results of this study suggest that the Harrington equation is preferable, particularly in patients of small stature and high BMI.