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Purpose: This study evaluated intraobserver reliability and construct validity of the squat test to assess lower extremity strength in children with cerebral palsy (CP) and spastic diplegia., Methods: Children with CP performed 2 trials of the squat test and calculated the intraclass correlation coefficient to evaluate intraobserver reliability. Correlations between outcomes of hand-held dynamometry (HHD) of knee extensor strength and an 8-repetition maximum (8RM) leg press test and the squat test were calculated to evaluate construct validity., Results: Excellent intraobserver reliability was observed for the squat test. Correlations between squat test performance and HHD knee extension and 8RM leg press test demonstrated good construct validity., Conclusions: The squat test is a reliable and valid tool to assess lower extremity strength in children with CP and spastic diplegia. The squat test is inexpensive and less time-consuming, and therefore particularly suitable for clinicians.

Background: Strength training programs for children with cerebral palsy (CP) showed inconclusive evidence for improving walking, despite improvements in strength. Recent studies have suggested that strength training with high movement velocity is more effective for improving walking than traditional resistance training., Objective: The purpose of this study was to evaluate the effect of functional high-velocity resistance training (power-training) to improve muscle strength and walking capacity of children with CP., Method: Twenty-two children with spastic CP participated (13 bilateral, Gross Motor Function Classification System [GMFCS] level I [n = 10] and II [n = 12], 7.5 years [SD 1.8, range 4-10 years]). Within-subjects changes in a 14-weeks usual care period were compared with changes in a 14-week functional power-training period (in groups, 3×/wk). Outcome measures were the muscle power sprint test (MPST), 1-minute walk test (1MWT), 10-m shuttle run test (SRT), gross motor function (GMFM-66), isometric strength of lower-limb muscles and dynamic ankle plantar flexor strength., Results: Changes during the training period were significantly larger than changes in the usual care period for all outcome measures ( P < .05). Large improvements were found during the training period for walking capacity (ΔMPST [mean]: 27.6 W [95%CI 15.84-39.46, 83% increase], Δ1MWT: 9.4 m [95% CI 4.17-14.68, 13%], ΔSRT: 4.2 [95%CI 2.57-5.83, 56%], ΔGMFM-66: 5.5 [95% CI 3.33-7.74, 7%]) and muscle strength (18%-128%), while outcomes remained stable in the usual care period., Conclusions: The results indicate that functional power-training is an effective training for improving walking capacity in young children with cerebral palsy.

Purpose: To determine the relationship between isometric leg muscle strength and mobility capacity in children with cerebral palsy (CP) compared to typically developing (TD) peers., Method: Participants were 62 children with CP (6-13 years), able to walk with (n = 10) or without (n = 52) walking aids, and 47 TD children. Isometric muscle strength of five muscle groups of the leg was measured using hand-held dynamometry. Mobility capacity was assessed with the 1-min walk, the 10-m walk, sit-to-stand, lateral-step-up and timed-stair tests., Results: Isometric strength of children with CP was reduced to 36-82% of TD. When adjusted for age and height, the percentage of variance in mobility capacity that was explained by isometric strength of the leg muscles was 21-24% (walking speed), 25% (sit-to-stand), 28% (lateral-step-up) and 35% (timed-stair) in children with CP. Hip abductors and knee flexors had the largest contribution to the explained variance, while knee extensors showed the weakest correlation. Weak or no associations were found between strength and mobility capacity in TD children., Conclusion: Isometric strength, especially hip abductor and knee flexor strength, is moderately related to mobility capacity in children with CP, but not in TD children. To what extent training of these muscle groups will lead to better mobility capacity needs further study. Implications for Rehabilitation Strength training in children with cerebral palsy (CP) may be targeted more specifically at hip abductors and knee flexors. The moderate associations imply that large improvements in mobility capacity may not be expected when strength increases.

Aim: To investigate the relation between muscle endurance and subjectively reported fatigue, walking capacity, and participation in mildly affected adolescents with cerebral palsy (CP) and peers with typical development., Method: In this case-control study, knee extensor muscle endurance was estimated from individual load-endurance curves as the load corresponding to a 15-repetition maximum in 17 adolescents with spastic CP (six males, 11 females; age 12-19y) and 18 adolescents with typical development (eight males, 10 females; age 13-19y). Questionnaires were used to assess subjectively reported fatigue (Pediatric Quality of Life Inventory Multidimensional Fatigue Scale) and participation (Life-Habits questionnaire). Walking capacity was assessed using the 6-minute walk test. Relations were determined using multiple regression analyses., Results: Muscle endurance related significantly to subjectively reported fatigue and walking capacity in adolescents with CP, while no relations were found for adolescents with typical development (subjectively reported fatigue: regression coefficient β [95% confidence intervals] for CP=23.72 [6.26 to 41.18], for controls=2.72 [-10.26 to 15.69]; walking capacity β for CP=125m [-87 to 337], for controls=2m [-86 to 89]). The 15-repetition maximum did not relate to participation in adolescents with CP., Interpretation: Subjectively reported fatigue and reduced walking capacity in adolescents with CP are partly caused by lower muscle endurance of knee extensors. Training of muscle endurance might contribute to reducing the experience of fatigue and improving walking capacity. Reduced muscle endurance seems to have no effect on participation., (© 2016 Mac Keith Press.)

Background: Quantifying leg muscle strength in young children with cerebral palsy (CP) is essential for identifying muscle groups for treatment and for monitoring progress., Aim: To study the feasibility, intratester reliability and the optimal test design (number of test occasions and repetitions) of measuring lower-limb strength with handheld dynamometry (HHD) and dynamic ankle plantar flexor strength with the standing heel-rise (SH) test in 3-10 year aged children with CP., Design: Test-retest design., Setting: Rehabilitation centre, special needs school for children with disabilities, and university medical centre., Methods: Knee extensor, hip abductor and calf muscle strength was assessed in 20 ambulatory children with spastic CP (3-5 years [N.=10] and 6-10 years [N.=10]) on two test occasions. Intraclass correlation coefficients (ICC) and Smallest Detectable Differences (SDD) were calculated to determine the optimal test design for detecting changes in strength., Results: All isometric strength tests had acceptable SDDs (9-30%), when taking the mean values of 2-3 test occasions (separate days) and 2-3 repetitions. The one-leg SH test had large SDDs (40-128% for younger group, 23-48% for older group)., Conclusion: Isometric strength (improvements) can only be measured reliably with HHD in young children with CP when the average values over at least 2 test occasions are taken. Reliability of the SH test is not sufficient for measuring individual changes in dynamic muscle strength in the younger children., Clinical Rehabilitation Impact: Results of this study can be used to determine the optimal number of test occasions and repetitions for reliable HHD measurements depending on expected changes, muscle group and age in 3-10 year old children with CP.

Aim: To combine peak torque and EMG analyses to investigate the hypothesis that 1) children with cerebral palsy (CP) have lower muscle fatigability than typically developing children (TD) and whether 2) muscle fatigue correlates with muscle strength., Methods: Seven CP children, eight TD children and ten young healthy adults (YHA) performed an all-out fatigue test of 35 maximal concentric knee extension and flexion contractions on an isokinetic dynamometer. Angular velocity was set at 60°/s. Peak torque (PT) was determined per repetition and either normalized to bodyweight or maximum voluntary torque. Surface-EMG of quadriceps and hamstring muscles was measured to obtain changes in median frequency (EMG-mf) and smooth rectified EMG amplitude per contraction., Results: Decline in PT differed between all groups for extensors and flexors, where YHA showed the largest decline and CP children the smallest decline over the course of the test. YHA showed a larger decline in EMG-mf of all quadriceps and hamstrings than TD and CP children, while TD children showed a larger decline in EMG-mf of m.rectus femoris and m.vastus lateralis than CP children., Interpretation: Results confirm that children with CP show lower fatigability than TD children and that the lower fatigability coincides with lower maximal muscle strength., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Background: Children with cerebral palsy (CP) typically show muscle weakness of the lower extremities, which can be measured with the use of handheld dynamometry (HHD)., Objective: The purposes of this study were: (1) to determine test-retest reliability and measurement error of isometric lower-extremity strength measurements in children with CP with the use of HHD and (2) to assess implications for measurement design., Design: A test-retest design was used., Methods: Fourteen children with hemiplegic (n=6) or diplegic (n=8) spastic CP (Gross Motor Function Classification System levels I-III), ages 7 to 13 years, were assessed for isometric strength on 2 separate days (occasions) with the use of HHD, with 3 trials per muscle group. The intraclass correlation coefficient, standard error of measurement, and smallest detectable difference (SDD) were calculated for different measurement designs., Results: Intraclass correlation coefficient values of single measurements for all muscle groups ranged from .70 to .90, and the SDD was large (>30%). Regarding measurement error, the largest source of variability was found for occasion. A 2-occasion mean decreased the SDD by 9% to 14%. For trials, a greater improvement in SDD was found when 2 trials were averaged instead of 3. A measurement design of 2 trials-2 occasions was superior to the often-used approach of 3 trials-1 occasion., Limitations: The small sample size was the major study limitation., Conclusions: Handheld dynamometry is reliable and can be used to detect changes in isometric muscle strength in children with CP when using the mean of at least 2 trials. To further improve reliability, taking the average of 2 occasions on separate days is recommended, depending on group size and muscle group.

Objective: To compare: (i) muscle strength, sprint power and maximal aerobic capacity; and (ii) the correlations between these variables in adults with and without cerebral palsy., Design: Cross-sectional study., Subjects: Twenty adults with and 24 without cerebral palsy., Methods: Isometric and isokinetic knee extension strength, sprint power (mean power over the 30s (P30)), peak aerobic power output (PO(peak)) and oxygen uptake (VO(2peak)) were determined. Regression analysis was used to investigate correlations between parameters., Results: Adults with cerebral palsy had significantly lower strength (53-69%) and P30 (67%) than adults without cerebral palsy, but similar PO(peak) and VO(2peak). In adults without cerebral palsy the only significant correlations, albeit weak, were between P30 and isometric (R2 = 0.34) or isokinetic strength (R2 = 0.20), as well as the correlation between P30 and VO(peak) (R2 = 0.26) or PO(peak) (R2 = 0.36). Stronger correlations were found in the group with cerebral palsy between P30 and isometric (R2 = 0.52) and isokinetic strength (R2 = 0.71) and between P30 and VO(peak) (R2 = 0.75) or PO(peak) (R2 = 0.94)., Conclusion: In contrast to aerobic capacity, strength and P30 are reduced in (active) people with cerebral palsy. Stronger correlations were found between strength, P30 and PO(peak) in adults with cerebral palsy. Therefore, muscle strength may be the limiting factor in adults with cerebral palsy for activities involving the lower extremities, such as cycling.

Aim: The aim of this study was to analyse the feasibility and reliability of the tests used to determine muscle strength, sprint power, and aerobic capacity in athletes and non-athletes with cerebral palsy (CP)., Methods: Twenty individuals with spastic CP (four females, 16 males; age range 18-49y; Gross Motor Function Classification System level I, n=15; II, n=5; unilateral CP, n=10; bilateral CP, n=10; athletes, n=12; non-athletes, n=8) participated in the study. Isometric and isokinetic knee flexor and extensor strength, sprint power, and aerobic capacity were determined, using, respectively an isokinetic dynamometer, a Wingate cycling test, and a graded maximal bicycle exercise test, on three occasions. Intraclass correlation coefficients (ICC), standard error of measurements, and smallest detectable differences (SDD) were calculated., Results: The feasibility of the isometric strength test, Wingate test, and graded exercise test was good; the isokinetic strength test was difficult to perform for five participants. The strength parameters showed moderate to good ICCs (isometric, 0.74-0.94; isokinetic, 0.88-0.93) but high SDDs (isometric, 25-45%; isokinetic, 30-45%). Sprint power (ICC 0.98; SDD 24%) and aerobic capacity (ICC 0.98-0.99; SDD 16-21%) showed good ICCs and moderate SDDs., Interpretation: All tests, except for the isokinetic strength test, seemed to be feasible for almost all participants. All tests are suitable for evaluating changes in a group; however, only large improvements (16-45%) can be detected when monitoring individual changes., (© The Authors. Developmental Medicine & Child Neurology © 2012 Mac Keith Press.)

The purpose of this study was to determine the association between isometric muscle strength of the lower limbs and gait joint kinetics in adolescents and young adults with cerebral palsy (CP). Twenty-five participants (11 males) with bilateral spastic CP, aged 14-22 years (mean: 18.9, sd: 2.0 yr) and Gross Motor Function Classification System (GMFCS) level II (n=19) and III (n=6) were tested. Hand held dynamometry was used to measure isometric strength (expressed in Nm/kg) of the hip, knee, and ankle muscles using standardized testing positions and procedures. 3D gait analysis was performed with a VICON system to calculate joint kinetics in the hip, knee and ankle during gait. Ankle peak moments exceeded by far the levels of isometric strength of the plantar flexors, while the knee and hip peak moments were just at or below maximal isometric strength of knee and hip muscles. Isometric muscle strength showed weak to moderate correlations with peak ankle and hip extension moment and power during walking. Despite considerable muscle weakness, joint moment curves were similar to norm values. Results suggest that passive stretch of the muscle-tendon complex of the triceps surae contributes to the ankle moment during walking and that muscle strength assessment may provide additional information to gait kinetics., (Copyright © 2010 Elsevier B.V. All rights reserved.)

Aim: To evaluate the effectiveness of functional progressive resistance exercise (PRE) strength training on muscle strength and mobility in children with cerebral palsy (CP)., Method: Fifty-one children with spastic uni- and bilateral CP; (29 males, 22 females; mean age 10 y 5 mo, SD 1 y 10 mo, range 6 y 0 mo-13 y 10 mo; Gross Motor Function Classification System levels I-III) were randomized to the intervention group (n=26) or the control group (n=25, receiving usual care). The intervention group trained for 12 weeks, three times a week, on a five-exercise circuit, which included a leg-press and functional exercises. The training load progressively increased based on the child's maximum level of strength, determined by the eight-repetition maximum. Muscle strength (measured with hand-held dynamometry and a six-repetition maximum leg-press test), mobility (measured with the Gross Motor Function Measure, two functional tests, and a mobility questionnaire), and spasticity (measured by the appearance of a catch) were evaluated before, during, directly after, and 6 weeks after the end of training by two blinded research assistants., Results: Directly after training, there was a statistically significant effect (p<0.05) on muscle strength (knee extensors +12% [0.56 N/kg; 95% confidence interval {CI} 0.13-0.99]; hip abductors +11% [0.27 N/kg; 95% CI 0.00-0.54]; total +8% [1.30 N/kg; 95% CI 0.56-2.54]; six-repetition maximum +14% [14%; 95% CI 1.99-26.35]), but not on mobility or spasticity. A detraining effect was seen after 6 weeks., Interpretation: Twelve weeks of functional PRE strength training increases muscle strength up to 14%. This strength gain did not lead to improved mobility.

Background: Until recently, strength training in children with cerebral palsy (CP) was considered to be inappropriate, because it could lead to increased spasticity or abnormal movement patterns. However, the results of recent studies suggest that progressive strength training can lead to increased strength and improved function, but low methodological quality and incomplete reporting on the training protocols hampers adequate interpretation of the results. This paper describes the design and training protocol of a randomized controlled trial to assess the effects of a school-based progressive functional strength training program for children with CP., Methods/results: Fifty-one children with Gross Motor Function Classification Systems levels I to III, aged of 6 to 13 years, were recruited. Using stratified randomization, each child was assigned to an intervention group (strength training) or a control group (usual care). The strength training was given in groups of 4-5 children, 3 times a week, for a period of 12 weeks. Each training session focussed on four exercises out of a 5-exercise circuit. The training load was gradually increased based on the child's maximum level of strength, as determined by the 8 Repetition Maximum (8 RM). To evaluate the effectiveness of the training, all children were evaluated before, during, directly after, and 6 weeks after the intervention period. Primary outcomes in this study were gross motor function (measured with the Gross Motor Function Measure and functional muscle strength tests) and walking ability (measured with the 10-meter, the 1-minute and the timed stair test). Secondary outcomes were lower limb muscle strength (measured with a 6 RM test, isometric strength tests, and a sprint capacity test), mobility (measured with a mobility questionnaire), and sport activities (measured with the Children's Assessment of Participation and Enjoyment). Spasticity and range of motion were assessed to evaluate any adverse events., Conclusion: Randomized clinical trials are considered to present the highest level of evidence. Nevertheless, it is of utmost importance to report on the design, the applied evaluation methods, and all elements of the intervention, to ensure adequate interpretation of the results and to facilitate implementation of the intervention in clinical practice if the results are positive., Trial Registration: Trial Register NTR1403.

Objective: To develop prognostic models for physical capacity at discharge and 1 year after discharge from inpatient rehabilitation in persons with spinal cord injury (SCI)., Design: Inception cohort; data collected at start of rehabilitation (n=104), at discharge (n=81), and 1 year later (n=74)., Setting: Eight Dutch rehabilitation centers., Participants: Patients with SCI at initial rehabilitation., Interventions: Not applicable., Main Outcome Measures: Physical capacity determined by endurance capacity (peak oxygen uptake [VO2peak, in L/min] and power output [POpeak, in watts]) during a maximal exercise test, arm muscle strength, and respiratory function. Multiple regression models, either with or without prior outcome, evaluated subject, lifestyle, and lesion-related predictors., Results: Only start VO2peak contributed to the prediction of discharge VO2peak (R2=.51). Discharge VO2peak contributed to its prediction 1 year later (R2=.75). Start POpeak, sex, age, and level of lesion contributed to discharge POpeak (R2=.73). Discharge POpeak, hours of employment before injury, and level of lesion contributed to POpeak 1 year later (R2=.81). Models without prior outcome explained less variance. Education, employment, body mass index, not smoking, and conservative stabilization of the spine positively contributed to endurance capacity. Muscle strength was well predicted (R2 range, .68-.84). Without prior outcome, respiratory function was poorly predicted., Conclusions: Because prior outcome contributed to an accurate prediction, the early assessment of physical capacity is important in establishing prognoses. Although their accuracy warrants caution in their application, models could complement clinical expertise when informing patients about expected physical outcome and identifying those at risk of low physical capacity.