Roles of reflex activity and co-contraction during assessments of spasticity of the knee flexor and knee extensor muscles in children with cerebral palsy and different functional levels

Muscle Activity and Co-Activation of Gait Cycle during Walking in Water and on Land in People with Spastic Cerebral Palsy

BACKGROUND

The purpose of this study was to investigate the differences in the muscle activity and co-activation index (CoA) of the rectus femoris (RF), biceps femoris (BF), gastrocnemius medialis (GM,) and tibialis anterior (TA) during walking on land and in water in healthy adolescents compared with those with spastic diplegia cerebral palsy (CP) adolescents.

METHODS

Four healthy individuals (median; age: 14 years, height: 1.57 cm, BMI: 16.58 kg/m²) and nine CP individuals (median; age: 15 years, height: 1.42 cm, BMI: 17.82 kg/m²) participated in this study and performed three walking trials under both conditions. An electromyography (EMG) collection was recorded with a wireless system Cometa miniwave infinity waterproof device, and the signals were collected using customized software named EMG and Motion Tools, Inc. software version 7 (Cometa slr, Milan, Italy) and was synchronized with an underwater VDO camera.

RESULTS

A significant decrease in the muscle activity of all muscles and CoA of RF/BF muscles, but an increase in TA/GM was observed within the CP group while walking in water during the stance phase. Between groups, there was a lower CoA of RF/BF and a greater CoA of TA/GM during the stance phase while walking in water and on land in the CP group. A non-significant difference was observed within the healthy group.

CONCLUSION

Walking in water can decrease muscle activity in lower limbs and co-activation of thigh muscles in people with spastic CP, whereas CoA muscles around ankle joints increased to stabilize foot weight acceptance.

To What Degree Does Limb Spasticity Affect Motor Performance in Para-Footballers With Cerebral Palsy?

Spasticity is considered a contributor to hypertonia, frequently presented in people with cerebral palsy (CP), affecting muscle function and motor activities. In CP football, the classification system determines that this impairment is eligible for competitive para-sports due to the impact on activity limitation and sports performance. However, the relationship between this feature (i.e., spastic hypertonia) and performance determinants has not been explored yet. This study aimed to assess the association of clinical spasticity measurements with the performance of sport-specific tests used for classification purposes. Sixty-nine international footballers with CP voluntarily participated in this study. The Australian Spasticity Assessment Scale was used to measure spasticity in lower limbs muscle groups and activity limitation tests were conducted considering dynamic balance, coordination, vertical and horizontal jumps, acceleration, and change of direction ability. Low-to-moderate negative significant associations were found between the hip spasticity and measures of dynamic balance and dominant unipedal horizontal jump capacity. Additionally, moderate associations were reported between the knee spasticity and the non-dominant unipedal horizontal jump capacity and the change of direction actions with the ball. The ankle spasticity score reported small to moderate associations with the change of direction assessment without the ball and bipedal and dominant unipedal horizontal jump capability. Finally, the total spasticity score only presented a significant association with horizontal jump performance. This is a novel study that provides evidence of the associations between an eligible neural impairment and relevant specific measures of activity limitation tests. These results suggest that the amount of spasticity according to each evaluated joint muscle group of the lower limbs presents a low-to-moderate significant relationship with determined measures of dynamic balance, coordination, horizontal jump, acceleration, and change of direction ability with and without the ball in international-level CP footballers. Further studies are necessary to elucidate the real contribution of neural and non-neural impairments related to hypertonia on fundamental sport-specific motor skills of para-footballers with CP.

Inter-machine reliability of the Biodex and Cybex isokinetic dynamometers for knee flexor/extensor isometric, concentric and eccentric tests

OBJECTIVES

To assess the inter-machine reliability of the Biodex System 3 Pro and Cybex Humac Norm Model 770 dynamometers for knee extensor and knee flexor peak torque measurements in isometric, concentric and eccentric tests.

DESIGN

Randomized/crossover.

SETTING

Exercise Research Laboratory, Federal University of Rio Grande do Sul (Brazil).

PARTICIPANTS

25 healthy male subjects.

MAIN OUTCOME MEASURES

Isometric, concentric and eccentric knee extensor and knee flexor peak torques recorded in the same test procedure performed on both isokinetic dynamometers. One-way ANOVA, intraclass correlation coefficient (ICC), standard error of measurement (SEM) and coefficient of variation (CV) were used to verify significant differences, relative and absolute reliability between devices.

RESULTS

No significant differences were found between tests performed on Biodex and Cybex (p > 0.05). ICC values indicated a high to very high reproducibility for isometric, concentric and eccentric peak torques (0.88-0.92), and moderate to high reliability for agonist-antagonist strength ratios (0.62-0.73). Peak torque did not show great difference between dynamometers for SEM (3.72-11.27 Nm) and CV (5.27-7.77%). Strength ratios presented CV values of 8.57-10.72%.

CONCLUSION

Maximal knee extensor and knee flexor tests performed in isometric (60° of knee flexion), concentric and eccentric modes at 60°/s in Biodex and Cybex dynamometers present similar values.

The relationship between spasticity and muscle volume of the knee extensors in children with cerebral palsy

PURPOSE

The purpose of this study was to examine the relationship between spasticity and muscle volume in children with cerebral palsy (CP), using isokinetic dynamometry and magnetic resonance imaging.

METHODS

A retrospective sample of 8 children with diplegic CP was analyzed. One set of 10 passive knee flexion movements was completed at a velocity of 180° per second with concurrent surface electromyography of the medial hamstrings (MH) and vastus lateralis (VL) to assess knee extensor spasticity. Magnetic resonance imaging was used to measure maximum cross-sectional area and muscle volume of the quadriceps femoris.

RESULTS

The quadriceps femoris muscle volume was positively correlated with MH reflex activity, VL reflex activity, MH/VL co-contraction, and peak knee extensor passive torque (P < .05).

CONCLUSION

The present findings suggest that higher levels of knee extensor muscle spasticity are associated with greater quadriceps muscle volume in children with spastic diplegic CP.

Hamstring contractures in children with spastic cerebral palsy result from a stiffer extracellular matrix and increased in vivo sarcomere length

Cerebral palsy (CP) results from an upper motoneuron (UMN)lesion in the developing brain. Secondary to the UMNl esion,which causes spasticity, is a pathological response by muscle - namely, contracture. However, the elements within muscle that increase passive mechanical stiffness, and therefore result in contracture, are unknown. Using hamstring muscle biopsies from pediatric patients with CP (n =33) and control (n =19) patients we investigated passive mechanical properties at the protein, cellular, tissue and architectural levels to identify the elements responsible for contracture. Titin isoform, the major load-bearing protein within muscle cells, was unaltered in CP. Correspondingly, the passive mechanics of individual muscle fibres were not altered. However, CP muscle bundles, which include fibres in their constituent ECM, were stiffer than control bundles. This corresponded to an increase in collagen content of CP muscles measured by hydroxyproline assay and observed using immunohistochemistry. In vivo sarcomere length of CP muscle measured during surgery was significantly longer than that predicted for control muscle. The combination of increased tissue stiffness and increased sarcomere length interact to increase stiffness greatly of the contracture tissue in vivo. These findings provide evidence that contracture formation is not the result of stiffening at the cellular level, but stiffening of the ECM with increased collagen and an increase of in vivo sarcomere length leading to higher passive stresses.

Relationship between age and spasticity in children with diplegic cerebral palsy

OBJECTIVE

To examine the relationship between passive torque, reflex activity, co-contraction, and age during the assessment of spasticity of knee flexors and extensors in children with spastic diplegic cerebral palsy (CP).

DESIGN

Retrospective.

SETTING

Pediatric orthopedic hospital.

PARTICIPANTS

Children (N=36) with spastic diplegic CP.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Spasticity of the knee flexors and knee extensors (as measured by peak passive torque, mean passive torque, reflex activity of the medial hamstrings, reflex activity of vastus lateralis, and co-contraction) was assessed during passive movements completed using an isokinetic dynamometer with concurrent electromyography.

RESULTS

A significant positive relationship was found between age and mean knee flexor passive torque (P<.05), while a significant negative relationship was found between age and mean percentage of the range of motion with co-contraction (P<.05).

CONCLUSIONS

Our results suggest that passive stiffness may play a larger role in spasticity than reflex activity as children with spastic diplegic CP age. Additional research is needed to determine whether subject age could influence the effectiveness of interventions, such as serial casting or botulinum toxin, for spasticity in children with spastic diplegic CP.

Age and electromyographic frequency alterations during walking in children with cerebral palsy

The use of surface electromyography (sEMG) recorded during ambulation has provided valuable insight into motor development and changes with age in the pediatric population. However, no studies have reported sEMG differences with age in the children with cerebral palsy (CP). In this study, data from 50 children were divided retrospectively into four groups, representing either an older (above the age of seven years) or younger (below the age of seven years) age group with either typical development (TD) or CP. Data were analyzed from 16 children in the younger age group with TD, and eight in the older age group with TD. Data were also available from 14 in the younger age group with CP, and 12 in the older age group with CP. SEMG signals from the rectus femoris (RF) and medial hamstring (MH) were analyzed using wavelet techniques to examine time-frequency content. RF muscle activity was statistically different between all groups (p<0.001), with an elevated instantaneous mean frequency (IMNF) in the older TD group than the younger TD group, an elevated IMNF in the younger CP group than the older CP group, and elevated IMNF in both CP groups compared to both TD groups. Activity for the MH muscle followed the same pattern except for the CP young and old group comparison, which indicated no difference. The results indicate that differences in neuromuscular activation exist between younger and older groups of children with both TD and CP, and may provide new insight into muscle activity pattern changes during the development of walking.