Article

Transverse plane pelvis rotations during walking may be regarded as the "first
determinant of gait". This would assume that pelvis rotations increase step
length, and thereby reduce the vertical movements of the centre of mass-"the
pelvic step". We analysed the pelvic step using 20 healthy young male subjects,
walking on a treadmill at 1-5 km/h, with normal or big steps. Step length, pelvis
rotation amplitude, leg-pelvis relative phase, and the contribution of pelvis
rotation to step length were calculated. When speed increased in normal walking,
pelvis rotation changed from more out-of-phase to in-phase with the upper leg.
Consequently, the contribution of pelvis rotation to step length was negative at
lower speeds, switching to positive at 3 km/h. With big steps, leg and pelvis
were more in-phase, and the contribution of pelvis rotation to step length was
always positive, and relatively large. Still, the overall contribution of pelvis
rotations to step length was small, less than 3%. Regression analysis revealed
that leg-pelvis relative phase predicted about 60% of the variance of this
contribution. The results of the present study suggest that, during normal slow
walking, pelvis rotations increase, rather than decrease, the vertical movements
of the centre of mass. With large steps, this does not happen, because leg and
pelvis are in-phase at all speeds. Finally, it has been suggested that patients
with hip flexion limitation may use larger pelvis rotations to increase step
length. This, however, may only work as long as the pelvis rotates in-phase with
the leg.
CI - Copyright (c) 2013 Elsevier B.V. All rights reserved.

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