Influence of vision on gait initiation and first step kinematics in young and older adults.

The study investigated whether anticipatory postural adjustments (APAs) of gait initiation and kinematics of the first step are modified with absence of vision in relation to age. Twenty-two young and twenty-two older subjects initiated a self-paced gait with the vision available and deprived. APAs were measured by: (1) force platform and evaluated by maximal amplitude of the center of pressure (CoP) displacements; (2) two inertial sensors attached to the trunk and evaluated by maximal accelerations. Step kinematics was recorded using a motion capture system and evaluated by duration, length and maximal velocity of the first step. Visual deprivation led to a significant reduction of forward trunk accelerations during the anticipatory phase of stepping in older adults. Moreover, they significantly reduced first step length and maximal velocity and prolonged duration of the first step. Contrary, young adults did not respond to absence of vision by significant changes of neither APAs, nor first step kinematics. These findings suggest that gait initiation is strongly associated with increased reliance on vision in older adults. We further indicate that trunk accelerations during the anticipatory phase of stepping may be a more sensitive measure to detect age-related changes of APAs due to absent visual information compared to CoP.

Postural changes during quiet stance and gait initiation in slightly obese adults.

The study is aimed to examine balance control of slightly obese young adults during quiet stance and during gait initiation with and without crossing an obstacle. Forty-four young subjects were divided in two groups: control (BMI<25 kg/m(2)) and slightly obese (BMI from 25 to 35 kg/m(2)). Center of foot pressure (CoP) and kinematics of fifth lumbar vertebra (L5) were evaluated using a force plate and a motion capture system. During quiet stance with eyes open slightly obese group showed increased mean amplitude and velocity of CoP in anterior-posterior direction compared to normal weight subjects. During unloading phase of gait initiation significantly greater and faster lateral CoP shift was observed in slightly obese group compared to normal weight peers. Presence of an obstacle increased amplitude and velocity of the lateral CoP shift similarly in both groups. No BMI-related differences were found on L5 segment during gait initiation, which may indicate that postural control was already successfully performed in feet (CoP). We have shown that increased CoP parameters values and thus increased postural instability during quiet stance and during unloading phase of gait initiation is present not only in morbidly obese, but already in slightly obese subjects.

Postural stability and responses to vibrations in patients after anterior cruciate ligament surgical reconstruction.

The aim of the study was to evaluate the effect of surgical reconstruction of anterior cruciate ligament (ACL) on postural stability and responses to lower limb (LL) muscles vibrations. Centre of pressure (CoP) was measured in 17 subjects during stance on firm/foam surface with eyes open/closed and during unilateral vibrations of LL muscles (m. triceps surae - TS, m. quadriceps femoris - Q, m. quadriceps femoris and hamstrings simultaneously - QH). The measurements were performed: 1) preoperatively, 2) six weeks and 3) three months after the reconstruction. Decreased postural stability was documented six weeks after the reconstruction compared to preoperative measurement. Three months after the reconstruction significant improvement was observed during stance on foam surface with eyes closed. Preoperatively, altered reactions of LL with ACL lesion compared to intact LL were manifested by slower response in first 3 s of TS vibration and by increased CoP shift in last 5 s of QH vibration. After the reconstruction, we observed slower CoP reaction and decreased CoP shift during TS vibration of LL with ACL lesion compared to preoperative level. Posturography during quiet stance and during TS vibration reliably detect postural changes due to ACL reconstruction and can be potentially useful in clinical practice.