In Normal Gait And Related Pelvic Muscle Activity

PurposeThe pelvic rotation of different walking speeds or steps has been studiedin order to clarify its contribution to the stride length. Moreover, the mechanismof pelvic rotation has been discussed to further investigate the role of hipmuscles activity.Material and Method20healthy young male subjects were asked to walk on a treadmill at5different velocities (1.0,2.0,3.0,4.0,5.0km/h), with normal or big step. Stridelength, amplitudes of pelvis, thorax and spinal rotations, timing relationships,and the contribution of pelvis rotation to stride length were calculated. Muscleactivity of Internal and External Oblique, Adductor Magnus, Adductor Longus,Gluteus Maximus, Gluteus Medius was recorded. Pelvic acceleration,estimated force of thorax, the legs were also calculated.Results(1) Contribution of pelvic rotation to stride lengthWith normal step, the pelvic rotation amplitude was firstly decreased andincreased from3km/h onwards, changing from out-of-phase to in-phase withthe upper leg. With big steps it was larger, and in-phase with the upper leg.The contribution of pelvic rotation to stride length was relatively small. It wasnegative at low speed with normal step, switching to positive at3km/h. Withbig step, it was always larger, and positive.(2) muscle activity in pelvic transverse rotationThere were four acceleration peaks of pelvic rotation in the gait cycle.The first negative peak had the largest impact on the leg-pelvis relative phase.The change of pelvic acceleration pattern with different speeds or steps wasmostly happened during double stance phase (about0-10%): when subjectswalked at lower speed, with normal step, pelvis continuously accelerated to right after left heel, while accelerated to left before left heel contact whenwalked with big step or with normal steps at high speed. The obvious muslceactivity only occurred at the first positive peak. However, it could be the“side-effect” of the activity of Gluteus Maximus, Gluteus Medius to keep thebody balance at the toe-off.ConclusionsThe contribution of pelvis rotation to stride length was small but important,and may be bigger in pathology, or in walking on an irregular surface. Themechanism of pelvic could not mostly explained by the activity of hip muscles.Passive mechanisms such as force of legs or thorax may play a moreimportant role in driving pelvic roation.