Ankle foot orthoses in cerebral palsy: Effects of ankle stiffness on trunk kinematics, gait stability and energy cost of walking.

In children with cerebral palsy (CP), rigid ventral shell ankle-foot orthoses (vAFOs) are often prescribed to reduce excessive knee flexion in stance and lower the energy cost of walking (ECW). However, how vAFOs affect ECW is a complex issue, as vAFOs may have an impact on lower limb biomechanics, upper body movements, and balance. Besides, the vAFO's biomechanical effect have been shown to be dependent on its stiffness around the ankle joint. We examined whether vAFO stiffness influences trunk movements and gait stability in CP, and whether there is a relationship between these factors and ECW. Fifteen children with spastic CP were prescribed vAFOs. Stiffness was varied into a rigid, stiff and flexible configuration. At baseline (shoes-only) and for each vAFO stiffness configuration, 3D-gait analyses and ECW-tests were performed. From the gait analyses, we derived trunk tilt, lateroflexion, and rotation range of motion (RoM) and the mediolateral and anteroposterior Margins of Stability (MoS) and their variability as measures of gait stability. With the ECW-test we determined the netEC. We found that wearing vAFOs significantly increased trunk lateroflexion (Wald χ2 = 33.7, p < 0.001), rotation RoM (Wald χ2 = 20.5, p < 0.001) and mediolateral gait instability (Wald χ2 = 10.4, p = 0.016). The extent of these effects partly depended on the stiffness of the vAFO. Significant relations between trunk movements, gait stability and ECW were found r = 0.57-0.81, p < 0.05), which indicates that trunk movements and gait stability should be taken into account when prescribing vAFOs to improve gait in children with CP walking with excessive knee flexion.

Locomotor training with body weight support in SCI: EMG improvement is more optimally expressed at a low testing speed.

STUDY DESIGN: Case series. OBJECTIVES: To determine the optimal testing speed at which the recovery of the EMG (electromyographic) activity should be assessed during and after body weight supported (BWS) locomotor training. SETTING: Tertiary hospital, Sint Maartenskliniek, Nijmegen, The Netherlands. METHODS: Four participants with incomplete chronic SCI were included for BWS locomotor training; one AIS-C and three AIS-D (according to the ASIA (American Spinal Injury Association) Impairment Scale or AIS). All were at least 5 years after injury. The SCI participants were trained three times a week for a period of 6 weeks. They improved their locomotor function in terms of higher walking speed, less BWS and less assistance needed. To investigate which treadmill speed for EMG assessment reflects the functional improvement most adequately, all participants were assessed weekly using the same two speeds (0.5 and 1.5 km h(-1), referred to as low and high speed, respectively) for 6 weeks. The change in root mean square EMG (RMS EMG) was assessed in four leg muscles; biceps femoris, rectus femoris, gastrocnemius medialis and tibialis anterior. RESULTS: The changes in RMS EMG occurred at similar phases of the step cycle for both walking conditions, but these changes were larger when the treadmill was set at a low speed (0.5 km h(-1)). CONCLUSION: Improvement in gait is feasible with BWS treadmill training even long after injury. The EMG changes after treadmill training are more optimally expressed using a low rather than a high testing treadmill speed.

Arm sway holds sway: locomotor-like modulation of leg reflexes when arms swing in alternation.

It has been argued that arm movements are important during human gait because they affect leg activity due to neural coupling between arms and legs. Consequently, one would expect that locomotor-like alternating arm swing is more effective than in-phase swing in affecting the legs' motor output. Other alternating movements such as trunk rotation associated to arm swing could also affect leg reflexes. Here, we assessed how locomotor-like movement patterns would affect soleus H-reflexes in 13 subjects performing arm swing in the sagittal plane (ipsilateral, contralateral and bilateral in-phase versus locomotor-like anti-phase arm movements) and trunk rotation with the legs stationary, and leg stepping with the arms stationary. Findings revealed that soleus H-reflexes were suppressed for all arm, trunk or leg movements. However, a marked reflex modulation occurred during locomotor-like anti-phase arm swing, as was also the case during leg stepping, and this modulation flattened out during in-phase arm swing. This modulation had a peculiar bell shape and showed maximum suppression at a moment where the heel-strike would occur during a normal walking cycle. Furthermore, this modulation was independent from electromyographic activity, suggesting a spinal processing at premotoneuronal level. Therefore, trunk movement can affect legs' output, and a special neural coupling occurs between arms and legs when arms move in alternation. This may have implications for gait rehabilitation.

Three-dimensional head and trunk movement characteristics during gait in children with spastic diplegia.

This study uses a recently developed trunk model to determine which head and trunk kinematic parameters differentiate children with spastic diplegia from typically developing (TD) children while walking. Differences in head and trunk parameters in relation to the severity of the motor involvement (GMFCS levels) were additionally examined. The trunk model consisted of five segments (pelvis, thorax, head, shoulder line, spine). Discrete kinematic parameters (ROM, mean position) and angular waveforms were compared between 20 children with spastic diplegia (age 9.8 years±2.9 years; GMFCS I: n=10, GMFCS II: n=10) and 20 individually age-matched TD children (9.7 years±3 years). A new measure for overall trunk pathology, the trunk profile score (TPS), was proposed and included in the comparative analysis. Compared to TD children, children with GMFCS II showed a significantly higher TPS and increased ROM for pelvis tilt, for thorax and head in nearly all planes, and the angle of kyphosis. In children with GMFCS I, only ROM of thorax lateral bending was significantly increased. Sagittal ROM differentiated best between GMFCS levels, with higher ROM found in children with GMFCS II. Current results provide new insights into head and trunk kinematics during gait in children with spastic diplegia.

Turning and unilateral cueing in Parkinson's disease patients with and without freezing of gait.

BACKGROUND: Freezing of gait (FOG) is one of the most disabling symptoms in Parkinson's disease (PD), and cueing has been reported to improve FOG during straight-line walking. Studies on how cueing affects FOG during turning are lacking. Given the asymmetrical nature of turning and the asymmetrical disease expression, we aimed to gain a new perspective on how unilateral cueing may alleviate FOG. OBJECTIVE: To explore disease dominance and turning side as contributing factors to turning problems and FOG and to investigate the effect of unilateral cueing. METHODS: In the first study, 13 PD patients with FOG (freezers) and 13 without FOG (nonfreezers) turned toward their disease-dominant and nondominant side (off medication). During the second study, 16 freezers and 14 nonfreezers turned with and without a unilateral auditory cue at -10% of preferred cadence. Total number of steps, turn duration, cadence, and FOG episodes were measured using VICON. RESULTS: Cadence, but not FOG frequency, was higher when turning toward the disease-dominant side. FOG started more frequently (64.9%) on the inner side of the turning cycle. Unilateral cueing seemed to prevent FOG in most patients, irrespective of the side at which the cue was offered. A carryover effect was found for cadence during turning, but the effect on FOG disappeared when the cue was removed. CONCLUSIONS: The occurrence of FOG is not influenced by turning toward the disease-dominant or nondominant side, which is confirmed by the fact that it does not make a difference at which side unilateral cueing is applied. Cueing reduces FOG during turning, but these effects disappear dramatically after cue removal. This raises further questions as to the influence of training on cue dependency and on the feasibility of either continuous application of cues or using cognitive strategies as an alternative.

To what extent is mean EMG frequency during gait a reflection of functional muscle strength in children with cerebral palsy?

The aim of the current paper was to analyze the potential of the mean EMG frequency, recorded during 3D gait analysis (3DGA), for the evaluation of functional muscle strength in children with cerebral palsy (CP). As walking velocity is known to also influence EMG frequency, it was investigated to which extent the mean EMG frequency is a reflection of underlying muscle strength and/or the applied walking velocity. Surface EMG data of the lateral gastrocnemius (LGAS) and medial hamstrings (MEH) were collected during 3DGA. For each muscle, 20 CP children characterized by a weak and 20 characterized by a strong muscle (LGAS or MEH) were selected. A weak muscle was defined as a manual muscle testing score <3; a strong muscle was defined as a manual muscle testing score ≥4. Patient selection was based on the following inclusion criteria: (a) predominantly spastic type of CP (3-15 years old), (b) either (near) normal muscle strength or muscle weakness in at least one of the studied lower limb muscles, (c) no lower limb Botulinum Toxin-A treatment within 6 months prior to the 3DGA, (d) no history of lower limb surgery, and (e) high-quality noise-free EMG-data. For each muscle, twenty age-related typically developing (TD) children were included as controls. In both muscles a consistent pattern of increasing mean EMG frequency with decreasing muscle strength was observed. This was significant in the LGAS (TD versus weak CP). Walking velocity also had a significant effect on mean EMG frequency in the LGAS. Furthermore, based on R(2) and partial correlations, it could be concluded that both walking velocity and muscle strength have an impact on EMG, but the contribution of muscle strength was always higher. These findings underscore the potential of the mean EMG frequency recorded during 3DGA, for the evaluation of functional muscle strength in children with CP.