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The authors investigated the effect on the oscillation of the twelfth thoracic and the second sacral vertebrae of healthy individuals during level walking when accommodative foot orthoses are used. Three-dimensional motion analysis was performed on eight healthy young male adults, fitted bilaterally with separated-arms foot orthoses while performing gait trials. Six spherical retroreflective skin-mounted markers were placed at specific anatomical points. Each participant performed six consecutive gait cycles at self-selected speed under three experimental conditions: barefoot, shod, and shod with insoles. Kinematic variables were then calculated, and repeated measures one-way analysis of variance and Tukey-Kramer multiple comparison tests were performed to characterize the differences observed among the test conditions. Statistically significant differences were found for the range of motion, the range of velocity, the maximum position and the maximum velocity instants of the thoracic vertebra, and for the range of motion and the maximum velocity instant of the sacrum. From these differences, the maximum position and the maximum velocity instants of the thoracic vertebra and the maximum velocity instant of the sacrum are attributed to the use of the orthoses. In addition, the increment of the damping ratio of both vertebrae, associated with the dissipation effect of the orthoses, was clear. These results indicate that there are some immediate effects of the tested foot orthoses on the oscillation pattern of the lower spine of the examined group. These insoles might contribute to motion-related low back pain prevention or relief; however, the actual mechanism remains unclear, so additional investigation is needed.

The authors investigated how normal subjects respond, in terms of the motion of their lower limbs, pelvis, and trunk, during level walking when fitted with mass-produced separated medial and lateral arms insoles. Three-dimensional gait analysis was performed on eight healthy male adults, fitted bilaterally with the tested orthosis. Eighteen spherical retroreflective skin-mounted markers were placed at specific anatomical points. Each participant performed six consecutive gait cycles at self-selected speed under three experimental conditions barefoot, shod, and shod with insoles. Kinematic variables were then calculated and one-way analysis of variance and Tukey-Kramer multiple comparisons tests were performed to characterize the differences observed among the test conditions. When the separated-arms insoles were used, the kinematics of the lower limb joints, pelvis, and trunk at the sagittal plane were not significantly affected, with the exception of the ankle joint. At the frontal plane, significant differences were found for both the hip joint and trunk, whereas at the transverse plane, significant differences were found for the ankle-foot complex only. The ankle-foot motion at the frontal plane and the hip joint motion at the transverse plane were not analyzed because of a high level of noise. All subjects but one exhibited consistently lower gait cycle and stance phase duration and increased stride length, walking speed, and cadence when changing from the shod to the insole condition. Our results indicate that there are immediate effects of the separated-arms foot orthoses to the walking pattern of the examined group. However, the way these insoles affect the lower limbs, pelvis, and trunk regarding relief of pain and fatigue remains unclear.