| Objective:We collected kinematic data of 12 C cup women in condition of wearing and not wearing sports bra and they walked at 6 km/h speed of three stride frequency. The kinematics of different breast supporting condition and the kinematic parameters of breast of different stride frequency were analyzed. To reveal the influence of different breast supporting condition on the human body movement and the effect of stride frequency’s change on breast movement, and to provide theoretical reference for the sports bra’s design and manufacture, and to advise consumers to choose bra.Methods:Using Qualisys Track Manager high-speed infrared motion capture system (10 cameras) to collect the kinematic data of the reflective markers,sampling frequency was 200 Hz. Stick point solutions adopted Helen-hayes model combined with five points on the breast (nipple (M1), the point upper nipple (MU), the point under nipple (MD), the point inside nipple (MI) and the point outside nipple (MO)), and relative coordinate transforming points were sternal angle point, thoracic point (equal altitude with sternal angle point) and the eighth thoracic point. Subjects randomly wore sports bra or with no bra walk 6 minutes at 6 km/h speed of three stride frequency, between each group they had a 6 min rest. Step frequency 1 was the natural frequency,step frequency 2 was step frequency 1’s 110%, step frequency 3 is the step frequency 1’s 90%. Statistical methods were two-factor variance analysis and multi-factor repetitive measure analysis of variance, the subsequent inspection was LSD method, significant level a= 0.05.Results:When wearing sports bra,the upper trunk angle was smaller compared to bare-breasted condition(p<0.05); the range of angles of trunk flexion and trunk torsion was smaller compared to bare-breasted condition while walking(p<0.05). The standard deviation of trunk flexion angle and trunk torsion angle of 10 gait cycles had significant difference(p<0.05), the standard deviation of trunk flexion angle when wearing sports bra was smaller compared to bare-breasted condition. The breast’s supporting condition had significant influence on range and standard deviation of displacement and velocity of different breast points in different directions, wearing sports bra induced a smaller range and standard deviation of breast points’ displacement and velocity(p<0.05), and the smallest displacement was in Y axis, the largest displacement was in X axis. Step frequency had significant influence on the range of upper trunk angle, trunk flexion angle and trunk torsion angle(p<0.05). The step frequency 3 has the biggest displacement range than the other two step frequency, the displacement of horizontal direction increased more than Z axis while the step frequency increasing. Different directions of the breast points’ displacement had significant differences and the displacement of Y axis is the largest and the X axis’is the smallest(p< 0.05). The velocity in Z axis of the step frequency 2 was bigger than step frequency 1 and step frequency 3.Conclusion:1. Sports bra changed breast’s shape,and had lifting and gathering effect. The displacement of breast in Y axis was the largest one of three directions and sports bra limited breast’s displacement and velocity.2.Different breast supporting condition have significant influence on the upper trunk angle, trunk flexion angle and trunk torsion angle. In bare-breasted condition, the upper trunk stretched more and the degrees of trunk flexion angle and trunk torsion angle became bigger, and walking without a sports bra reduced the stability of walking.3.Different step frequency changed the trunk flexion angle and trunk torsion angle, it affected the displacement of the breast in horizontal direction. The displacement of breast became larger when step frequency decreased. |
PDF Full Text Request