Time-frequency analysis of surface electromyographic signals during fatiguing isokinetic muscle actions

The purpose of this study was to use a wavelet analysis designed specifically for electromyography (EMG) signals in combination with a trend plot to examine changes in EMG intensity patterns during maximal, fatiguing isokinetic muscle actions. Eleven men (mean ± SD age = 22.4 ± 1.1 years) and 7 women (mean ± SD age = 22.7 ± 2.1 years) performed 50 consecutive maximal concentric isokinetic muscle actions of the dominant leg extensors at a velocity of 180°·s(-1). During each muscle action, a bipolar surface EMG signal was detected from the vastus lateralis. All signals were then processed with a wavelet analysis designed specifically for EMG signals, which resulted in EMG intensity patterns. The patterns for each subject were then analyzed with a trend plot, which provided information regarding the changes that occurred because of fatigue. The results indicated that for all the 18 subjects, the EMG intensity patterns moved in a predictable manner in pattern space, but the changes to the patterns were different for each subject. These findings reflect the complex changes that occur in the EMG signal during fatigue. These changes cannot be characterized fully with a single amplitude and center frequency parameter and can be useful for athletes and coaches who need to track the fatigue status of individual muscles.     

Life expectancy in children with cerebral palsy.

OBJECTIVE--To determine life expectancy of children with cerebral palsy. DESIGN--Cohort analysis, by means of register compiled from multiple sources of ascertainment, of all children with cerebral palsy born during 1966-84 to mothers resident in Mersey region. Status of children was determined by flagging through NHS central register. SUBJECTS--1258 subjects with idiopathic cerebral palsy, of whom 1251 were traced and included in analysis. MAIN OUTCOME MEASURES--Effect of functional ability (ambulation, manual dexterity, and mental ability), sex, birth weight, and gestational age on survival. RESULTS--20 year survival for whole cohort was 89.3% for females and 86.9% for males. For subjects with no severe functional disabilities 20 year survival was 99% (95% confidence interval 98% to 100%), while subjects severely disabled in all three functional groups had 20 year survival of 50% (42% to 58%). Subjects with birth weight < or = 2500 g had 20 year survival of 92% (89% to 95%), while those with birth weight > 2500 g had survival of 87% (84% to 89%). Subjects with gestational age of > 37 weeks had 20 year survival of 93% (91% to 96%), while those with gestational age > or = 37 weeks had survival of 85% (83% to 88%). Birth weight and gestational age were less predictive of survival than functional disability. Best statistical model used gestational age and number of severe functional disabilities as predictors. CONCLUSIONS--Life expectancy of this cohort of children with cerebral palsy was greater than has been suggested in some previous studies. This has important implications for social, educational, and health services.     

Ocular defects in children with cerebral palsy.

Children with cerebral palsy have a high incidence of ocular abnormalities. All such children should be examined by an ophthalmologist soon after cerebral palsy is diagnosed.     

The effect of corrective surgery on energy expenditure during ambulation in children with cerebral palsy

Mechanical efficiency, heart rate, blood lactate, and some other variables were studied in six children with cerebral palsy who walked on a treadmill before and after corrective surgery. During each test, conducted at each child's naturally selected speed, two situations were studied: steady state level walking for 9 min, and then walking at an increasing inclination up to 20% for another 10 min. During the test the subjects were allowed to hold on to a handrail to eliminate the risk of falling off the treadmill. The corrective surgery resulted in a 5% reduction in oxygen consumption per kg body mass during level walking. The subjects' levels of physical fitness, as estimated from oxygen pulse, however, were unchanged. These results are indicative of a biomechanical improvement due to the corrective surgery. While walking at a 20% inclination the subjects off loaded themselves to different degrees on the handrail which influenced the results. Their feeling of exhaustion at this load was probably due to local factors, since heart rate was well below maximal values, and blood lactate, respiratory exchange ratio and ventilatory equivalent also indicated that they were below their anaerobic thresholds (50-60% of maximal oxygen uptake).     

Changes in masticatory muscle activity in children with cerebral palsy

The objective of the study was to determine whether children with cerebral palsy (CP) have abnormal bilateral masseter and temporal muscle activation during mastication. The muscular activity of 32 children aged between 7 and 13 years was assessed during the task of non-habitual mastication by means of surface electromyograms. During non-habitual mastication, the amplitude of all assessed muscles in the inactive period and the amplitude of the Right Masseter and Left Temporal muscles in the active period of children with CP was greater (p < 0.05) in relation to the group of children with Typical Development (TD). Considering each muscle individually, only the duration of the active period of Right Masseter and Right Temporal muscles in children with CP was lower (p < 0.05) than in the TD children. Considering the four analyzed muscles, the duration of time of general active period, when at least one muscle should be activated, was higher in children with CP (p < 0.05) than in children with TD showing greater time variation in inactivation (p < 0.05). The higher muscle activity during the phases of the masticatory cycle, with longer duration of the active period and with greater variability between the muscles to inhibit this activity show greater difficulty in coordinating the muscles of mastication in children with CP compared to children with TD.     

Dental health and dental care in children with cerebral palsy

The aim of this study was to determine a difference between children with cerebral palsy (CP) and healthy children, regarding health condition of teeth and oral tissuses. Disfunction of masticatory system, in children with CP, causes many problems with mastication. Nonfunctional mastication is related with the consumption of mushy food and decreased selfcleaning of occlusal and aproximal surfaces. All that leads to higher incidence of dental caries. Comparing the DMTF/dft (decayed, missing, filled tooth) index, it is evident that there is no statistically significant difference in a tooth morbidity between the group of healthy children and group of children with CP. The healthy children have statistically significant more teeth with fillings with respect to children with CP. Extractions are more common in children with CP. There is no statistically significant difference between those two groups regarding decayed teeth, one of components of DMFT index. Decayed components are more common than the extractions and fillings in both groups, which shows the insufficient curative care for all children in both groups. It can be concluded that there is a certain need of early beginning and a better organization of the preventive pediatric and dental care, in order to decrease the appearence of dental decay and increase the level of dental health, in this challenged population.     

Altered sense of Agency in children with spastic cerebral palsy

Background  

Children diagnosed with spastic Cerebral Palsy (CP) often show perceptual and cognitive problems, which may contribute to their functional deficit. Here we investigated if altered ability to determine whether an observed movement is performed by themselves (sense of agency) contributes to the motor deficit in children with CP.     

Antioxidant enzymes and lipid peroxides in children with cerebral palsy

Impaired antioxidant mechanisms are unable to inactivate free radicals that may induce a number of pathophysiological processes and result in cell injury. Thus, any abnormality in antioxidant defense systems could affect neurodevelopmental processes and could have an important role in the etiology of cerebral palsy (CP). The plasma levels of lipid peroxidation as plasma levels of malondialdehyde (MDA), activities of superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione reductase (GR) in plasma and erythrocytes were investigated in 34 CP children and compared with 61 normal controls. SOD, GPx and GR activities were spectrophotometrically assayed. Activities of SOD, GPx and GR in plasma did not differ significantly between CP children and the control group. Activities of erythrocyte GR in the CP patients were significantly lower compared with controls. MDA concentration did not differ statistically between the CP children and healthy subjects. In conclusion our results suggest that increased activities of erythrocyte GPx and decreased erythrocyte GR activities might be due to lesser physical activity of children with CP.     

Mechanobiological prediction of proximal femoral deformities in children with cerebral palsy

Children with cerebral palsy (CP) walk with altered gait and frequently exhibit proximal femoral deformities, such as anteversion and coxa valga. The objective of this research was to investigate the effect of specific gait patterns on the femoral morphology in CP.

In this study, the mechanobiological principles were implemented on a 3D finite element (FE) model of the proximal femur in order to predict changes in morphology over time in healthy and CP children. This model relies on the assumption that cyclic octahedral shear stress promotes growth and cyclic hydrostatic compressive stress inhibits growth. Growth was simulated over 16 iterations, representing approximately 5 months of growth.

The FE model predicts an increase in the femoral anteversion and coxa valga for CP loading conditions when compared with healthy ones. Understanding the role of loading in skeletal morphogenesis may help prevent bone deformities and improve function in children with gait abnormalities.     

Quantifying muscle activity in non-ambulatory children with spastic cerebral palsy before and after selective dorsal rhizotomy.

Cerebral palsy is a condition that results in varying degrees of functional deficits. The goal of this study was to develop an objective measure of muscle activity during a prescribed voluntary motor task in non-ambulatory children with spastic cerebral palsy. While performing a simultaneous hip/knee flexion task from the supine position, followed by return to the starting position, electromyographic and kinematic data were obtained from the right leg of eight children before and after selective dorsal rhizotomy and compared with eight age-matched controls. The electromyographic and kinematic data were combined to determine for each muscle of interest (tibialis anterior, soleus, vastus lateralis, biceps femoris) the percentage of the movement cycle for which the muscle was acting concentrically, eccentrically, isometrically or was considered inactive. Averaged over the four muscles, isometric activity decreased by 38% post-op and the time the muscles were inactive increased by 37% following surgery. The percentages of concentric and eccentric activity did not differ significantly between pre- and post-op conditions. Post-operatively, the percentage muscle activity patterns of the children with cerebral palsy more closely resembled that of the control children: averaged across all muscles and contraction types, the difference between the control children and the children with cerebral palsy was reduced by 50% following surgery. This measurement technique indicates promise as a method for quantifying muscle activity during voluntary motor tasks in non-ambulatory children with cerebral palsy.     

Time-frequency filtering of MEG signals with matching pursuit.

Time-frequency signal analysis based on various decomposition techniques is widely used in biomedical applications. Matching Pursuit is a new adaptive approach for time-frequency decomposition of such biomedical signals. Its advantage is that it creates a concise signal approximation with the help of a small set of Gabor atoms chosen iteratively from a large and redundant set. In this paper, the usage of Matching Pursuit for time-frequency filtering of biomagnetic signals is proposed. The technique was validated on artificial signals and its performance was tested for varying signal-to-noise ratios using both simulated and real MEG somatic evoked magnetic field data.     

Serum trace element and amino acid profile in children with cerebral palsy

BackgroundThe existing data demonstrate that both trace elements and amino acids play a significant role in neurodevelopment and brain functioning. Certain studies have demonstrated alteration of micronutrient status in children with cerebral palsy, although multiple inconsistencies exist.The objectiveof the present study was to assess serum trace element and mineral, as well as amino acid levels in children with cerebral palsy.Methods71 children with cerebral palsy (39 boys and 32 girls, 5.7 ± 2.3 y.o.) and 84 healthy children (51 boys and 33 girls, 5.4 ± 2.3 y.o.) were enrolled in the present study. Serum trace element and mineral levels were assessed using inductively-coupled plasma mass-spectrometry (ICP-MS). Amino acid profile was evaluated by means of high-pressure liquid chromatography (HPLC).ResultsChildren with cerebral palsy are characterized by significantly lower Cu and Zn levels by 6% and 8%, whereas serum I concentration exceeded the control values by 7%. A tendency to increased serum Mn and Se levels was also observed in patients with cerebral palsy. Serum citrulline, leucine, tyrosine, and valine levels were 15 %, 23 %, 15 %, and 11 % lower than those in healthy controls. Nearly twofold lower levels of serum proline were accompanied by a 44 % elevation of hydroxyproline concentrations when compared to the control values. In multiple regression model serum I, Zn, and hydroxyproline levels were found to be independently associated with the presence of cerebral palsy. Correlation analysis demonstrated a significant correlation between Cu, Mn, Se, I, and Zn levels with hydroxyproline and citrulline concentrations.ConclusionThe observed alterations in trace element and amino acid metabolism may contribute to neurological deterioration in cerebral palsy. However, the cross-sectional design of the study does not allow to estimate the causal trilateral relationships between cerebral palsy, altered trace element, and amino acid metabolism.     

Electrophysiologic studies in selective dorsal rhizotomy for spasticity in children with cerebral palsy

A group of 20 children with spastic cerebral palsy underwent selective dorsal rhizotomy for alleviation of spasticity. Pre- and postoperatively, cortical somatosensory evoked responses (cSSEP), H reflex and F wave studies were done. Clinically there was dramatic reduction of tone without noticeable sensory loss. The electrophysiologic studies showed several findings: (1) many children have abnormal cSSEP preoperatively; (2) surgery seldom leads to a loss of cSSEP; (3) in many patients, there is a noteworthy improvement in the cSSEP wave form; (4) some children have electrophysiologic evidence of spinal cord dysfunction preoperatively and (5) Hmax/Mmax ratio decreases after surgery confirming decrease in tone.