Trunk postural reactions to the force perturbation intensity and frequency during sitting astride in children with cerebral palsy.

The purpose of this study was to examine kinematic and neuromuscular responses of the head and body to pelvis perturbations with different intensities and frequencies during sitting astride in children with CP. Sixteen children with spastic CP (mean age 7.4 ± 2.4 years old) were recruited in this study. A custom designed cable-driven robotic horse was used to apply controlled force perturbations to the pelvis during sitting astride. Each participant was tested in four force intensity conditions (i.e., 10%, 15%, 20%, and 25% of body weight (BW), frequency = 1 Hz), and six force frequency conditions (i.e., 0.5 Hz, 1 Hz, 1.5 Hz, 2 Hz, 2.5 Hz, and 3 Hz, intensity = 20% of BW). Each testing session lasted for one minute with a one-minute rest break inserted between two sessions. Kinematic data of the head, trunk, and legs were recorded using wearable sensors, and EMG signals of neck, trunk, and leg muscles were recorded. Children with CP showed direction-specific trunk and neck muscle activity in response to the pelvis perturbations during sitting astride. Greater EMG activities of trunk and neck muscles were observed for the greater intensities of force perturbations (P < .05). Participants also showed enhanced activation of antagonistic muscles rather than direction-specific trunk and neck muscle activities for the conditions of higher frequency perturbations (P < .05). Children with CP may modulate trunk and neck muscle activities in response to greater changes in intensity of pelvis perturbation during sitting astride. Perturbations with too high frequency may be less effective in inducing direction-specific trunk and neck muscle activities.

Overground walking with a constraint force on the nonparetic leg during swing improves weight shift toward the paretic side in people after stroke.

Targeting enhancing the use of the paretic leg during locomotor practice might improve motor function of the paretic leg. The purpose of this study was to determine whether application of constraint force to the nonparetic leg in the posterior direction during overground walking would enhance the use of the paretic leg in people with chronic stroke. Fifteen individuals after stroke participated in two experimental conditions, i.e., overground walking with a constraint force applied to the nonparetic leg and overground walking only. Each participant was tested in the following procedures that consisted of overground walking with either constraint force or no constraint force, instrumented split-belt treadmill walking, and pressure-sensitive gait mat walking before and after the overground walking. Overground walking practice with constraint force resulted in greater enhancement in lateral weight shift toward the paretic side (P < 0.01), muscle activity of the paretic hip abductors (P = 0.04), and propulsion force of the paretic leg (P = 0.05) compared with the results of the no-constraint condition. Overground walking practice with constraint force tended to induce greater increase in self-selected overground walking speed (P = 0.06) compared with the effect of the no-constraint condition. The increase in propulsion force from the paretic leg was positively correlated with the increase in self-selected walking speed (r = 0.6, P = 0.03). Overground walking with constraint force applied to the nonparetic leg during swing phase of gait may enhance use of the paretic leg, improve weight shifting toward the paretic side and propulsion of the paretic leg, and consequently increase walking speed.NEW & NOTEWORTHY Application of constraint force to the nonparetic leg during overground walking induced improved lateral weight shifts toward the paretic leg and enhanced muscle activity of the paretic leg during walking. In addition, one session of overground walking with constraint force might induce an increase in propulsive force of the paretic leg and an increase in self-selected overground walking speed, which might be partially due to the improvement in motor control of the paretic leg.

Improving Trunk Postural Control Facilitates Walking in Children With Cerebral Palsy: A Pilot Study.

OBJECTIVE: The aim of this study is to determine the effects of bilateral trunk support during walking on trunk and leg kinematics and neuromuscular responses in children with cerebral palsy. DESIGN: Fourteen children with spastic cerebral palsy (Gross Motor Function Classification System level I to III) participated in this study. Children walked on a treadmill under four different conditions, that is, without support (Baseline), with bilateral support applied to the upper trunk (upper trunk support), the lower trunk (lower trunk support), and combined upper and lower trunk (combined trunk support). The trunk and leg kinematics and muscle activity were recorded. RESULTS: Providing bilateral support to the trunk had a significant impact on the displacement of the pelvis and trunk ( P < 0.003) during walking. Children's weaker leg showed greater step length ( P = 0.032) and step height ( P = 0.012) in combined trunk support compared with baseline and greater step length in upper trunk support ( P = 0.02) and combined trunk support ( P = 0.022) compared with lower trunk support. Changes in soleus electromyographic activity during stance phase of gait mirrored the changes in step length across all conditions. CONCLUSIONS: Providing bilateral upper or combined upper and lower trunk support during walking may induce improvements in gait performance, which may be due to improved pelvis kinematics. Improving trunk postural control may facilitate walking in children with cerebral palsy.

Enhanced phasic sensory afferents paired with controlled constraint force improve weight shift toward the paretic side in individuals post-stroke.

PURPOSE: The goal of this study was to determine whether enhanced phasic sensory afferent input paired with the application of controlled constraint force during walking would improve weight shift toward the paretic side and enhance use of the paretic leg. METHODS: Fourteen stroke survivors participated in two experimental conditions, sessions that consisted of 1 min treadmill walking without force and stimulation (baseline), 7 min walking with either "constraint force and sensory stimulation (constraint+stim)" or "constraint force only (constraint)" (adaptation), and then 2 min walking without force and stimulation (post-adaptation). Kinematics of the pelvis and legs, and muscle activity of the paretic leg were recorded. RESULTS: Participants showed greater increases in hip abductor (p < 0.001) and adductor (p = 0.04) muscle activities, weight shift toward the paretic side (p = 0.002), and step length symmetry (p < 0.01) during the late post-adaptation period in the "constraint+stim" condition, compared with the effect of the "constraint" condition. In addition, changes in overground walking speed from baseline to 10 min post treadmill walking was significantly greater for the "constraint force and stimulation" condition than for the "constraint force only" condition (p = 0.04). CONCLUSION: Enhanced targeted sensory afferent input during locomotor training may facilitate recruitment of targeted muscles of the paretic leg and facilitate use-dependent motor learning of locomotor tasks, which might retain longer and partially transfer from treadmill to overground walking, in stroke survivors.

Swing-phase pelvis perturbation improves dynamic lateral balance during walking in individuals with spinal cord injury.

The purpose of this study was to determine whether the control of lateral balance can be improved by applying repeated lateral perturbation force to the pelvis during swing versus stance phase walking in individuals with spinal cord injury (SCI). Fourteen individuals with incomplete SCI were recruited in this study. Each participant visited the lab once and was tested in two experimental sessions that consisted of (1) treadmill walking with bilateral perturbation force applied to the pelvis in the lateral direction during either swing or stance phase of each leg and (2) overground walking pre- and post-treadmill walking. Applying the swing-phase perturbation during walking induced a greater increase in the muscle activation of hip abductors and ankle plantar flexors and a greater improvement in lateral balance control after the removal of perturbation force, in comparison to the results of the stance-phase perturbation condition (P ≤ 0.03). Participants also exhibited a greater reduction in overground step width and a greater improvement in overground walking speed after a session of treadmill walking practice with the swing-phase perturbation, compared with the result of the stance-phase perturbation (P = 0.01). These findings suggest that applying perturbation force to the pelvis during the swing phase of gait while walking may enhance muscle activities of hip abductors and improve lateral balance control in individuals with SCI. A walking practice with the swing-phase pelvis perturbation can be used as a rehabilitation approach to improve the control of lateral balance during walking in people with SCI.