Changes in muscle activation following ankle strength training in children with spastic cerebral palsy: an electromyography feasibility case report

ABSTRACT Children with cerebral palsy (CP) are likely to experience decreased participation in activities and less competence in activities of daily living. Studies of children with spastic CP have shown that strengthening programs produce positive results in strength, gait, and functional outcomes (measured by the Gross Motor Function Measure). No investigations have analyzed electromyography (EMG) activity before and after strength training to determine whether any changes occur in the GMFM.  This feasibility case report quantified dorsiflexor and plantarflexor muscle activation changes during performance of 3-5 selected GMFM items following a plantarflexor strength training in two children with cerebral palsy. Increased plantarflexor strength and increased ability to selectively activate muscles were found. Little carryover to performance on GMFM items was observed. It is feasible to use EMG during performance on selected GMFM items to evaluate motor control changes following strength training in children with CP.

Robotics and gaming to improve ankle strength, motor control, and function in children with cerebral palsy--a case study series

The objective of this study was to investigate the feasibility of game-based robotic training of the ankle in children with cerebral palsy (CP). The design was a case study, 12 weeks intervention, with no follow-up. The setting was a university research laboratory. The participants were a referred sample of three children with cerebral palsy, age 7-12, all male. All completed the intervention. Participants trained on the Rutgers Ankle CP system for 36 rehabilitation sessions (12 weeks, three times/week), playing two custom virtual reality games. The games were played while participants were seated, and trained one ankle at-a-time for strength, motor control, and coordination. The primary study outcome measures were for impairment (DF/PF torques, DF initial contact angle and gait speed), function (GMFM), and quality of life (Peds QL). Secondary outcome measures relate to game performance (game scores as reflective of ankle motor control and endurance). Gait function improved substantially in ankle kinematics, speed and endurance. Overall function (GMFM) indicated improvements that were typical of other ankle strength training programs. Quality of life increased beyond what would be considered a minimal clinical important difference. Game performance improved in both games during the intervention. This feasibility study supports the assumption that game-based robotic training of the ankle benefits gait in children with CP. Game technology is appropriate for the age group and was well accepted by the participants. Additional studies are needed however, to quantify the level of benefit and compare the approach presented here to traditional methods of therapy.

Effects of a supported speed treadmill training exercise program on impairment and function for children with cerebral palsy

AIM

To compare the effects of a supported speed treadmill training exercise program (SSTTEP) with exercise on spasticity, strength, motor control, gait spatiotemporal parameters, gross motor skills, and physical function.

METHOD

Twenty-six children (14 males, 12 females; mean age 9y 6mo, SD 2y 2mo) with spastic cerebral palsy (CP; diplegia, n=12; triplegia, n=2; quadriplegia n=12; Gross Motor Function Classification System levels II-IV) were randomly assigned to the SSTTEP or exercise (strengthening) group. After a twice daily, 2-week induction, children continued the intervention at home 5 days a week for 10 weeks. Data collected at baseline, after 12-weeks' intervention, and 4 weeks after the intervention stopped included spasticity, motor control, and strength; gait spatiotemporal parameters; Gross Motor Function Measure (GMFM); and Pediatric Outcomes Data Collection Instrument (PODCI).

RESULTS

Gait speed, cadence, and PODCI global scores improved, with no difference between groups. No significant changes were seen in spasticity, strength, motor control, GMFM scores, or PODCI transfers and mobility. Post-hoc testing showed that gains in gait speed and PODCI global scores were maintained in the SSTTEP group after withdrawal of the intervention.

INTERPRETATION

Although our hypothesis that the SSTTEP group would have better outcomes was not supported, results are encouraging as children in both groups showed changes in function and gait. Only the SSTTEP group maintained gains after withdrawal of intervention.

Ankle control and strength training for children with cerebral palsy using the Rutgers Ankle CP: a case study

The purpose of the study described here was to develop and feasibility test the Rutgers Ankle CP, aimed at ankle strengthening and improved control for children with cerebral palsy (CP). The system was an upgrade in hardware (new foot attachment, new robot controller) and software (new games and programming language) of the earlier Rutgers Ankle in order to permit training of children with CP. The new Rutgers Ankle CP was used to train ankle strength and motor control in a 7 year old boy with CP during 36 rehabilitation sessions (12 weeks, 3 times/week). Assessments for impairment, function and quality of life were taken before and after training. Results indicated improvements in both strength and motor control. Gait function improved substantially in ankle kinematics, speed and endurance. Overall function (GMFM) indicated improvements that were typical of other ankle strength training programs. Quality of life increased beyond what would be considered a minimal clinical important difference. While these results are only for a single participant, they are very encouraging toward improving the function and quality of life of children with cerebral palsy. Further research with a larger number of participants is planned.

The pathophysiological basis of weakness in children with cerebral palsy

PURPOSE

To examine the evidence concerning the neurologic and muscular pathophysiology that contributes to clinically observed weakness in children and young people with cerebral palsy (CP).

METHOD

Literature concerning the neural or muscular changes in subjects with CP was found by searching 6 databases plus supplementary searching.

RESULTS

A final set of 51 articles was identified by 2 independent reviewers.

SUMMARY OF KEY POINTS

Muscle weakness is due to reduced central drive, possible abnormal neural maturation, insufficient and disorganized motor recruitment, impaired voluntary control, impaired reciprocal inhibition, altered setting of muscle spindles, and reinforcement of abnormal neural circuits. Muscle tissue is altered, with selective atrophy of fast fibers and altered myosin expression, changes in fiber length and cross-sectional area, changes in the length-tension curve, reduced elasticity, and impoverished muscle tissue development.

CONCLUSION

Children with CP are weak because of both neurologic and muscular changes.

Normalizing lower extremity strength data for children, adolescents, and young adults with cerebral palsy

The traditional method for normalizing quantitative strength data is to divide force or torque by body mass. We have previously shown that this method is not appropriate for able-bodied children and young adults and that normalization using allometric scaling is more effective. The purpose of the current study was to evaluate the effectiveness of applying existing normalization equations for lower extremity strength to children, adolescents, and young adults with cerebral palsy (CP) and, if appropriate, to develop CP-specific normalization equations using allometric scaling. We measured the maximum torque generated during hip abduction/adduction, knee extension/flexion, and ankle dorsiflexion/plantar flexion in 96 subjects with spastic diplegia CP ages 4-23 years. Traditional mass normalization (Torque/Mass1.0) and allometric scaling equations from children without disability (Torque/Mass1.6 for hip and knee; Torque/Mass1.4 for ankle) were not effective in eliminating the influence of body mass. Normalization using CP-specific allometric scaling equations was effective using both muscle-specific and common (Torque/Mass0.8 for ankle plantar flexors; Torque/Mass1.4 for all others) scaling relationships. For the first time, normalization equations have been presented with demonstrated effectiveness in adjusting strength measures for body size in a group of children, adolescents, and young adults with CP.

Use of Relative Phase as a Measure of Motor Control at the Ankle in Persons with Cerebral Palsy: A Preliminary Study

This investigation developed a measure of motor control at the ankle for persons with CP using relative phase. Twenty-nine subjects, 14 with spastic diplegia cerebral palsy (CP group) and 15 without disability (WD group) were tested once. Video data were collected as a seated subject performed four full range of ankle plantar and dorsiflexion movement tasks (right ankle, left ankle, ankles in-phase with each other, and ankles antiphase to each other) at four different frequencies (self-paced, 0.5, 0.75, 1.0 Hz). The relative phase measure was able to discern the differences between the two groups of children. The CP group had poorer motor control than the WD group, based upon the measure. Both groups had more difficulty performing the antiphase than the in-phase movements. The investigation adds to the body of knowledge in that the concept of relative phase was used as a measure of motor control at the ankle in persons with CP. Results indicated that the measure was adequately sensitive to quantify differences between a group with CP and a group without disability. Clinically the measure could eventually be used as both an assessment and outcome tool.

Relationships Between Spasticity, Strength, Gait, and the GMFM-66 in Persons With Spastic Diplegia Cerebral Palsy

OBJECTIVE

To determine the relationships between spasticity, strength, and the functional measures of gait and gross motor function in persons with spastic diplegia cerebral palsy (CP).

DESIGN

Retrospective, cross-sectional study.

SETTING

Hospital clinic.

PARTICIPANTS

Ninety-seven participants (49 boys, 48 girls; mean age+/-standard deviation, 9.11+/-4.8 y) with spastic diplegia CP were tested once.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

A KinCom dynamometer was used to objectively measure spasticity (ankle plantarflexors, knee flexors, hip adductors) and maximum strength (ankle dorsiflexors and plantarflexors, knee flexors and extensors, hip abductors and adductors). A gait analysis was conducted to evaluate linear variables (gait speed, stride length, cadence) and kinematic variables (ankle dorsiflexion, foot progression, knee and hip flexion, pelvic tilt at initial contact and ankle dorsiflexion, knee and hip flexion, pelvic tilt, trunk rotation range of motion) during gait. Gross motor function was measured using the Gross Motor Function Measure (GMFM-66) and separately, the GMFM walking, running & jumping dimension. Multiple linear regression analysis was used to determine the relationships between spasticity, strength, gait, and the GMFM (P<.05).

RESULTS

Spasticity did not account for a substantial amount of explained variance in gait and gross motor function (up to 8% for the GMFM walking, running & jumping dimension). Moderate to high correlations existed between strength and gait linear data and function, accounting for up to 69% of the explained variance (strength and GMFM-66, r2=.69).

CONCLUSIONS

For this cohort of participants with spastic diplegia CP who ambulated with or without an assistive device, strength was highly related to function and explained far more of the variance than spasticity. The results may not be generalized to those with more severe forms of CP.

Predicting functional change from preintervention measures in selective dorsal rhizotomy

OBJECT

In this investigation the authors attempted to predict change in function following selective dorsal rhizotomy (SDR) and intensive physical therapy in patients with spastic diplegic cerebral palsy (CP) based on multidomain preintervention measures.

METHODS

Data pertaining to 22 children with CP were collected before the SDR and again 20 months afterward. Although equations for predicting change in gait speed and function (such as the Gross Motor Function Measure) were derived, the 95% confidence interval (CI) widths were too broad to make accurate predictions that were clinically useful outside the study group.

CONCLUSIONS

Future work should be focused on developing additional measures such as lower-extremity motor control and balance in an attempt to reduce the CIs to more clinically relevant values.

Effect of selective dorsal rhizotomy in the treatment of children with cerebral palsy

OBJECT

In this investigation the authors compared impairment and functional outcomes between two groups of children with cerebral palsy (CP): one group underwent selective dorsal rhizotomy (SDR) followed by intensive physical therapy (PT), and the other group underwent the latter only (PT group). Data from an age-matched group of children without disability (nondisabled [ND] group) were also collected.

METHODS

Data pertaining to the 68 children with CP were collected before any intervention and again 8 and 20 months afterwards. Data regarding the 40 children in the ND group were collected in a single session.

CONCLUSIONS

Although patients in both groups with CP were weaker than those in the ND group, they did have strength gains. Gait speed in the SDR-PT group was slower than that in the ND group preoperatively but not at 20 months postoperatively. Gait speed in the PT group remained slower than that in the ND group. The pre- to postoperative change in the Gross Motor Abilities Estimate score was significantly greater in the SDR-PT group than in the PT-only group. An effective treatment for children with CP, SDR offers gains in strength, gait speed, and overall gross motor function.

Quantifying Active Ankle Range of Motion in Cerebral Palsy Following Selective Dorsal Rhizotomy

This study was conducted to determine whether an objective and quantitative measure for active ankle range of motion would be sensitive to differences between persons of able body and those with cerebral palsy (CP), and between pre- and postselective dorsal rhizotomy (SDR). Twelve children with spastic diplegia CP were tested before undergoing an SDR, and again after 8 months of intensive physical therapy (SDR group). Fourteen other children with spastic diplegia were tested initially and again 8 months following no intervention but maintaining their existing level of physical therapy (CP group). Twenty age-matched children of able body were tested once (AB group). A video system recorded active sagittal plane ankle movements as the seated child independently performed maximum dorsiflexion and plantarflexion. The data were tracked and analyzed to determine end-range dorsiflexion and plantarflexion, and total active ankle range of motion. Repeated-measures ANOVA and Tukey post hoc tests were used to test for significant differences among and between groups, p < 0. 05. Results for the SDR group indicated a significant increase in end-range dorsiflexion and total range of motion following the surgery, with no changes in any measures for the CP group. Results for both groups with CP indicated differences vs. the AB group. The measure provided additional information from what has previously been reported for active ankle range of motion. The integration of this measure with other objective measures for quantifying impairments and presurgical function may be useful in predicting post-SDR gait status and other functional activities.

A Measure of Motor Control at the Knee in Cerebral Palsy

This investigation developed a measure of motor control for the knee extensors in adults with cerebral palsy (CP). Four adults with CP and 4 able-bodied (AB) adults participated. A KinCom dynamometer rotated the knee from approximately 90º of knee flexion to 10º/s less than the participant’s maximum knee extension at a speed of 10º/s, while the participant attempted to match a 44.5-N “target” force. The average, standard deviation, and median frequency of the force-time data were used to describe the test results. The individual force values for the AB group were near the target force and clustered together. The values for the CP group were also near the target force, but displayed greater variation. The average standard deviation for the CP group was more than three times larger than that of the AB group. The average median frequency for the CP group was less than that of the AB group. Results pointed to differing strategies for each group as they attempted to match the target force. The AB group attempted to match the target force with frequent small-magnitude force changes, while the CP group attempted to match the target force with fewer oscillations of greater magnitude. The methods employed in the present investigation are initial attempts to quantify one aspect of motor control, a visually guided tracking task.

Hip Spasticity and Strength in Children with Spastic Diplegia Cerebral Palsy

Hip spasticity and strength from 44 children with cerebral palsy (CP) and 44 children with able bodies (AB) were compared. For spasticity, a KinCom dynamometer abducted the passive hip at 4 different speeds and recorded the resistive adductor torques. Work values for the torque-angle data were calculated at each speed. Linear regression derived the slope for the line of best fit for the work-velocity data to determine the spasticity measure. For strength, the KinCom rotated the hip from maximum adduction to maximum abduction at a speed of 10°/s while the child performed a maximum abduction concentric contraction. Tests were reversed to record maximum adduction. Maximum torques and work by the abductors and adductors were calculated. Spasticity in the adductors for the CP group was significantly greater than values recorded for the AB group. All strength measures were significantly less than the AB group. Results provide objective information, quantifying hip spasticity and strength in children with CP.

Changes in ankle spasticity and strength following selective dorsal rhizotomy and physical therapy for spastic cerebral palsy

OBJECT

In this investigation the authors quantified changes in ankle plantarflexor spasticity and strength following selective dorsal rhizotomy (SDR) and intensive physical therapy in patients with cerebral palsy (CP).

METHODS

Twenty-five patients with cerebral palsy (CP group) and 12 able-bodied volunteers (AB controls) were tested with a dynamometer. For the spasticity measure, the dynamometer was used to measure the resistive torque of the plantarflexors during passive ankle dorsiflexion at five different speeds. Data were processed to yield a single value that simultaneously encompassed the three key elements associated with spasticity: velocity, resistance, and stretch. For the strength test, the dynamometer rotated the ankle from full dorsiflexion to full plantarflexion while a maximum concentric contraction of the plantarflexors was performed. Torque angle data were processed to include the work done by the patient or volunteer on the machine. Plantarflexor spasticity values for the CP group were significantly greater than similar values for the AB control group prior to surgery but not significantly different after surgery. Plantarflexor strength values of the CP group were significantly less than those of the AB control group pre- and postsurgery. Postsurgery strength values did not change relative to presurgery values.

CONCLUSIONS

The spasticity results of the present investigation agreed with those of previous studies indicating a reduction in spasticity for the CP group. The strength results did not agree with the findings of most previous related literature, which indicated that a decrease in strength should have occurred. The strength results agreed with a previous investigation in which knee flexor strength was objectively examined, indicating that strength did not decrease as a consequence of an SDR. The methods of this investigation could be used to improve SDR patient selection.

Spasticity and strength changes as a function of selective dorsal rhizotomy

OBJECT

The goal of this investigation was to quantify changes in hamstring muscle spasticity and strength in children with cerebral palsy (CP) as a function of their having undergone a selective dorsal rhizotomy.

METHODS

Nineteen children with CP (CP group) and six children with able bodies (AB group) underwent testing with a dynamometer. For the spasticity measure, the dynamometer measured the resistive torque of the hamstring muscles during passive knee extension at four different speeds. Torque-angle data were processed to calculate the work done by the machine to extend the knee for each speed. Linear regression was used to calculate the slope of the line of best fit for the work-velocity data. The slope simultaneously encompassed three key elements associated with spasticity (velocity, resistance, and stretch) and was considered the measure of spasticity. For the strength test, the dynamometer moved the leg from full knee extension to flexion while a maximum concentric contraction of the hamstring muscles was performed. Torque-angle data were processed to calculate the work done on the machine by the child. Hamstring spasticity values for the CP group were significantly greater than similar values for the AB group prior to surgery; however, they were not significantly different after surgery. Hamstring strength values for the CP group remained significantly less than those for the AB group after surgery, but were significantly increased relative to their presurgery values.

CONCLUSIONS

The results of spasticity testing in the present investigation agreed with those of previous studies, indicating a reduction in spasticity for the CP group. The results of strength testing did not agree with those in the previous literature; a significant increase in strength was observed for the CP group.