Laura A. Prosser

Neuromuscular Electrical Stimulation Versus Volitional Isometric Strength Training in Children With Spastic Diplegic Cerebral Palsy: A Preliminary Study

Background. To date, no reports have investigated neuromuscular electrical stimulation (NMES) to increase muscle force production of children with cerebral palsy (CP) using high-force contractions and low repetitions. Objective. The aims of this study were to determine if isometric NMES or volitional training in children with CP could increase muscle strength and walking speed and to examine the mechanisms that may contribute to increased force production. Methods. Eleven children with spastic diplegia were assigned to an NMES training group or to a volitional training group. Participants in the NMES group had electrodes implanted percutaneously to activate the quadriceps femoris and triceps surae muscles. The volitional group trained with maximal effort contractions. Both groups performed a 12-week isometric strength-training program. Maximum voluntary isometric contraction (MVIC) force, voluntary muscle activation, quadriceps and triceps surae cross-sectional area (CSA), and walking speed were measured pre- and post-strength training. Results . The NMEStrained group had greater increases in normalized force production for both the quadriceps femoris and triceps surae. Similarly, only the NMES group showed an increase in walking speed after training. Changes in voluntary muscle activation explained approximately 67% and 37% of the changes seen in the MVIC of the NMES and volitional groups, respectively. Quadriceps femoris maximum CSA increased significantly for the NMES group only. Conclusions. This study was the first to quantitatively show strength gains with the use of NMES in children with CP. These results support the need for future experimental studies that will examine the clinical effectiveness of NMES strength training.

Trunk and Hip Muscle Activation Patterns Are Different During Walking in Young Children With and Without Cerebral Palsy

Background Poor control of postural muscles is a primary impairment in people with cerebral palsy (CP). Objective The purpose of this study was to investigate differences in the timing characteristics of trunk and hip muscle activity during walking in young children with CP compared with children with typical development (TD). Methods Thirty-one children (16 with TD, 15 with CP) with an average of 28.5 months of walking experience participated in this observational study. Electromyographic data were collected from 16 trunk and hip muscles as participants walked at a self-selected pace. A custom-written computer program determined onset and offset of activity. Activation and coactivation data were analyzed for group differences. Results The children with CP had greater total activation and coactivation for all muscles except the external oblique muscle and differences in the timing of activation for all muscles compared with the TD group. The implications of the observed muscle activation patterns are discussed in reference to existing postural control literature. Limitations The potential influence of recording activity from adjacent deep trunk muscles is discussed, as well as the influence of the use of an assistive device by some children with CP. Conclusions Young children with CP demonstrate excessive, nonreciprocal trunk and hip muscle activation during walking compared with children with TD. Future studies should investigate the efficacy of treatments to reduce excessive muscle activity and improve coordination of postural muscles in CP.

Trunk and hip muscle activity in early walkers with and without cerebral palsy--a frequency analysis.

Poor control of postural muscles is a primary impairment in cerebral palsy (CP), yet core trunk and hip muscle activity has not been thoroughly investigated. Frequency analysis of electromyographic (EMG) signals provides insight about the intensity and pattern of muscle activation, correlates with functional measures in CP, and is sensitive to change after intervention. The objective of this study was to investigate differences in trunk and hip muscle activation frequency in children with CP compared to children with similar amounts of walking experience and typical development (TD). EMG data from 31 children (15 with CP, 16 with TD) were recorded from 16 trunk and hip muscles bilaterally. A time-frequency pattern was generated using the continuous wavelet transform and instantaneous mean frequency (IMNF) was calculated at each interval of the gait cycle. Functional principal component analysis (PCA) revealed that IMNF was significantly higher in the CP group throughout the gait cycle for all muscles. Additionally, stride-to-stride variability was higher in the CP group. This evidence demonstrated altered patterns of trunk and hip muscle activation in CP, including increased rates of motor unit firing, increased number of recruited motor units, and/or decreased synchrony of motor units. These altered muscle activation patterns likely contribute to muscle fatigue and decreased biomechanical efficiency in children with CP.

Locomotor Training Within an Inpatient Rehabilitation Program After Pediatric Incomplete Spinal Cord Injury

Background and Purpose: The outcomes of intense locomotor training after incomplete spinal cord injury (SCI) have been described in adults with acute and chronic injuries and with various levels of ambulatory function. This case report describes a comprehensive inpatient rehabilitation program with a locomotor training component in a child with a severe incomplete SCI. Case Description: A 5-year-old girl injured at C4 participated in locomotor training for 5 months during inpatient rehabilitation. Outcomes: The patients Functional Independence Measure for Children II (WeeFIM II) mobility score increased from 5/35 to 21/35. Her Walking Index for Spinal Cord Injury II (WISCI II) score improved from 0 to 12. The patient returned to walking in the community with assistive devices. Discussion: It is feasible to include an intense locomotor training program in the clinical rehabilitation setting for a child with a severe SCI, and the outcomes were consistent with results in adults. Further investigation with experimental designs and more participants will determine the extent to which this intervention benefits the pediatric population with SCI.

Muscle Plasticity and Ankle Control After Repetitive Use of a Functional Electrical Stimulation Device for Foot Drop in Cerebral Palsy

Background/Objectives. The primary goal was to determine whether repetitive functional electrical stimulation (FES) for unilateral foot drop increases tibialis anterior (TA) muscle size compared with an untreated baseline and the contralateral side in cerebral palsy (CP). Secondary goals were to determine whether positive changes in muscle size and gait, if found, accumulated during the 3 intervals during which participants used the device. FES devices differ from traditional orthoses that often restrict muscle activation and may exacerbate weakness, promote continued dependence on orthoses, or precipitate functional decline. Methods. Participants were 14 independent ambulators with inadequate dorsiflexion in swing, with a mean age of 13.1 years, evaluated before and after the 3-month baseline, 1-month device accommodation, 3-month primary intervention, and 3-month follow-up phases. The FES device (WalkAide) stimulated the common fibular nerve to dorsiflex the ankle and evert the foot while monitoring use. TA muscle ultrasound, gait velocity, and ankle kinematic data for barefoot and device conditions are reported. Results. Ultrasound measures of TA anatomic cross-sectional area and muscle thickness increased in the intervention compared with baseline and with the contralateral side and were maintained at follow-up. Maximum ankle dorsiflexion decreased at baseline but improved or was maintained during the intervention phase with and without the device, respectively. Muscle size gains were preserved at follow-up, but barefoot ankle motion returned to baseline values. Conclusions. This FES device produced evidence of use-dependent muscle plasticity in CP. Permanent improvements in voluntary ankle control after repetitive stimulation were not demonstrated.

Variability and symmetry of gait in early walkers with and without bilateral cerebral palsy

PURPOSE Investigating gait characteristics during the early stages of walking in CP may contribute to the understanding of the development of impaired gait. The objective of this study was to investigate differences in the variability and symmetry of spatiotemporal gait characteristics during the early years of walking in children with bilateral spastic CP compared to children with similar amounts of walking experience and typical development (TD). METHODS The spatiotemporal gait parameters of 31 children (15 with spastic CP, 16 with TD) who had an average of 28.5 (18.1 SD) months of walking experience were collected using an instrumented walkway. RESULTS All primary spatiotemporal parameters were reduced in the CP group, who also demonstrated greater stride-to-stride variability, compared to the TD group. There were no statistically significant differences in side-to-side symmetry between groups. IMPLICATIONS Clinical trials investigating gait interventions during the early years of walking in children with CP should be conducted to determine if treatment can reduce the functional limitations that are present during the emergence of walking skills. Further investigation should examine variability and symmetry in the kinematics, kinetics, and muscle activity patterns of early walkers with CP, and the effect of treatment on the variability and symmetry of walking characteristics.

Acceptability and potential effectiveness of a foot drop stimulator in children and adolescents with cerebral palsy

Aim  Ankle–foot orthoses are the standard of care for foot drop in cerebral palsy (CP), but may overly constrain ankle movement and limit function in those with mild CP. Functional electrical stimulation (FES) may be a less restrictive and more effective alternative, but has rarely been used in CP. The primary objective of this study was to conduct the first trial in CP examining the acceptability and clinical effectiveness of a novel, commercially available device that delivers FES to stimulate ankle dorsiflexion.

Feasibility and preliminary effectiveness of a novel mobility training intervention in infants and toddlers with cerebral palsy

Objective: To design a novel mobility training intervention incorporating infant motor learning and neurorehabilitation principles and investigate its feasibility, tolerability and effect on motor development in toddlers with cerebral palsy (CP). Methods: A single-subject research design with repeated measures during 6-week baseline and intervention phases and after treatment withdrawal was used. Five participants attended therapy utilizing novel dynamic weight assistance technology, which allowed practice of motor skills beyond participants’ current abilities. Results: Average attendance and engagement rates exceeded 90%. Gains in gross motor function were observed after treatment that exceeded the expected rate in four of the five participants. Rates of motor development during treatment were 10.8, 3.8, 7.0, 15.1, and 0.3 times greater than during baseline for the five participants, respectively. Conclusions: This intervention was tolerated and demonstrated the potential to alter the trajectory of motor development in CP, providing proof of concept for further investigation.

Tibialis anterior architecture, strength, and gait in individuals with cerebral palsy.

Introduction: The relationship of tibialis anterior (TA) muscle architecture, including muscle thickness (MT), cross‐sectional area (CSA), pennation angle (PA), and fascicle length (FL), to strength and ankle function was examined in ambulatory individuals with CP and unilateral foot drop. Methods: Twenty individuals with CP participated in muscle ultrasound imaging, unilateral strength testing, and three‐dimensional gait analysis. Results: Muscle size (MT and CSA) was positively related to strength, fast gait velocity, and ankle kinematics during walking. Higher PA was related to a more dorsiflexed ankle position at initial contact and inversely with fast gait velocity. FL was related to strength, fast velocity, and step length at a self‐selected speed. Conclusions: Muscle architecture partially explains the degree of impairment in strength and ankle function in CP. Treatments to increase TA size and strength may produce some gait improvement, but other factors that may contribute to ankle performance deficits must be considered. Muscle Nerve, 2011

Comparison of elliptical training, stationary cycling, treadmill walking and overground walking. Electromyographic patterns.

The most common functional motor goal of lower extremity rehabilitation is to improve walking ability. For reasons of feasibility, safety or intensity, devices are frequently used to facilitate or augment gait training. The objective of this study was to compare the muscle activity patterns of the rectus femoris and semitendinosus muscles during four conditions: overground walking, treadmill walking, stationary cycling, and elliptical training. Ten healthy adults (six male, four female; mean age 22.7±2.9 years, range 20-29) participated and surface electromyographic data were recorded. Linear envelope curves were generated and time normalized from 0 to 100% cycle. The mean plus three standard deviations from a static trial was used as the threshold for muscle activity. Repeated measures analysis of variance procedures were used to detect differences between conditions. Elliptical training demonstrated greater rectus femoris activity and greater rectus femoris/semitendinosus coactivation than all other conditions. Consistent with previous work, treadmill walking demonstrated greater rectus femoris activity than overground walking. Minimal differences in semitendinosus activation were observed between conditions, limited to lower peak activity during cycling compared to treadmill walking. These results provide normative values for rectus femoris and semitendinosus activation for different locomotor training methods and may assist in selecting the most appropriate training device for specific patients. Clinicians and researchers should also consider the kinematic and kinetic differences between tasks, which cannot necessarily be inferred from muscle activation patterns.