Efficacy of transcutaneous electrical nerve stimulation combined with therapeutic exercise on hand function in children with hemiplegic cerebral palsy

Purpose: Transcutaneous electrical nerve stimulation (TENS) is a nonpharmacological method used to reduce spasticity. It was also assumed that TENS reduces pain and therefore improves limb function. Most of the previous studies about the effect of TENS were done in the lower limb and in stroke patients. There is a lack of enough literature about the direct and indirect effects of TENS in the upper limb. Hence, our study aimed to determine whether TENS combined with therapeutic exercises helps to improves hand function by reducing spasticity in children with hemiplegic cerebral palsy (CP).

Materials and methods: Twenty-nine children with hemiplegic CP were randomly assigned to the TENS group (n?=?15) or the control group (n?=?14). The TENS group received traditional physical therapy with the adjunct application of conventional TENS for 30?minutes (pulse duration, 250 µs; pulse rate, 100?Hz) on the wrist extensors, once daily, 3?days a week, for 8?weeks, while the control group received traditional physical therapy.

Results: The results showed a significant intergroup difference in handgrip strength over the 8-week period. The time to accomplish the Jebsen Taylor Hand Function Test (JTHFT) task decreased by 48% and the ABILHAND-Kids questionnaire scores improved by 23% in the TENS group.

Conclusions: The use of TENS in combination with therapeutic exercise may improve strength and hand function.     

Modulation of shoulder muscle and joint function using a powered upper-limb exoskeleton

Robotic-assistive exoskeletons can enable frequent repetitive movements without the presence of a full-time therapist; however, human-machine interaction and the capacity of powered exoskeletons to attenuate shoulder muscle and joint loading is poorly understood. This study aimed to quantify shoulder muscle and joint force during assisted activities of daily living using a powered robotic upper limb exoskeleton (ArmeoPower, Hocoma). Six healthy male subjects performed abduction, flexion, horizontal flexion, reaching and nose touching activities. These tasks were repeated under two conditions: (i) the exoskeleton compensating only for its own weight, and (ii) the exoskeleton providing full upper limb gravity compensation (i.e., weightlessness). Muscle EMG, joint kinematics and joint torques were simultaneously recorded, and shoulder muscle and joint forces calculated using personalized musculoskeletal models of each subject’s upper limb. The exoskeleton reduced peak joint torques, muscle forces and joint loading by up to 74.8% (0.113 Nm/kg), 88.8% (5.8%BW) and 68.4% (75.6%BW), respectively, with the degree of load attenuation strongly task dependent. The peak compressive, anterior and superior glenohumeral joint force during assisted nose touching was 36.4% (24.6%BW), 72.4% (13.1%BW) and 85.0% (17.2%BW) lower than that during unassisted nose touching, respectively. The present study showed that upper limb weight compensation using an assistive exoskeleton may increase glenohumeral joint stability, since deltoid muscle force, which is the primary contributor to superior glenohumeral joint shear, is attenuated; however, prominent exoskeleton interaction moments are required to position and control the upper limb in space, even under full gravity compensation conditions. The modeling framework and results may be useful in planning targeted upper limb robotic rehabilitation tasks.     

Morphological effects of electrical stimulation and intermittent muscle stretch after immobilization in soleus muscle

The objective of the present study was to assess the effectiveness of a combined protocol of muscle stretching and strengthening after immobilization of the hindlimb. Thirty female Wistar rats were divided into 6 groups: group immobilized for 14 days to cause full plantar flexion by cast (GI, n = 6); group immobilized/stretched (GIS, n = 6): submitted to the same immobilization and to 10 days of passive stretching; group immobilized/electrically stimulated (GIES, n = 6): similarly immobilized and submitted to 10 days of low frequency electrical stimulation (ES); group immobilized/stretched/electrically stimulated (GISES, n = 6): similarly immobilized, submitted to 10 days of stretching and ES application; group immobilized/free (GIF, n = 3): similarly immobilized and then left with free limbs for 10 days; control group (CG, n = 3). The middle portion of the soleus muscle was frozen and sections were stained with HE or mATPase. Morphological analysis revealed high cellular reactivity in the GISES, GIES and GIS groups. The lesser diameter and proportion of type I fibers (TIF) and type II fibers (TIIF) (at pH 9.4) and connective area (at HE stain) were measured with an image analyzer and the data obtained were analyzed statistically by the unpaired Student t-test (p < or = 0.05). The results indicated that: a) immobilization generated atrophy of both fiber types (p < 0.05); b) joint application of ES and stretching was not efficient in reestablishing the size of the two fiber types compared to CG (p < 0.05); c) the ES protocol reestablished only the size of TIIF, which showed values similar to those detected in CG (p < 0.05); d) the stretch increased the proliferation of the perimysium connective tissue (p < 0.05). Thus, we conclude that, in the model applied here to female rats, a stretching protocol may limit the volume protein gain of soleus muscle fibers and increase the connective interstitial tissue.     

Reduction of the muscle activity associated with self-imposed electrical stimulation of mixed nerves supplying lower limb muscles in man.

Similarly to brief hammer taps self-imposed on the limb segments, self-triggered electrical stimulation delivered to the tibial, femoral or peroneal nerves are associated with anticipatory reduction in the muscle activity (RMA) of the target leg muscles. The anticipatory RMA starts shortly before the expected perturbation and lasts until the onset of the impact. The purpose of the present work is to study to what extent the selective activation of the different homonymous and heteronymous afferents could modify the central programs and the associated time and space distribution of the anticipatory RMA pattern in the target leg muscles. Our results show that the anticipatory RMA pattern is a result mainly of a pre-programmed non-specific central command, rather than consequence of the specific composition of the afferent volleys originating from different homonymous and heteronymous nerves. The commands for the voluntary movement triggering the stimulation and the associated anticipatory RMA are closely linked but independently controlled. By their synchronisation and co-ordination the central nervous system accounts the differences in length of the particular motor pathways. It is suggested, that in contrast to the classic anticipatory postural adjustments, the anticipatory RMA is presumably an alternative mode of feed-forward control diminishing the undesired effects of the afferent inputs.     

Comparison of contractile function of diaphragm and cardiac muscle in response to paired electrical stimulation

Paired pacing has been shown to potentiate contractile function of cardiac muscle, and it has been suggested that this may enhance contractile function of diaphragmatic muscle. The primary goal of this study was to study the effect of paired pacing on potentiation of contractile function of diaphragmatic muscle compared to atrial and ventricular myocardium. Diaphragmatic muscle was isolated from mouse and rat, and atrial and ventricular myocardium from dogs. Potentiation was induced by isolated extrastimuli (equal in duration and intensity to the pacing stimulus) and by repetitive extrastimuli (i.e. paired pacing) at a paced rate of 12, 30 and 60 beats/min. Baseline studies were performed while preparations were isometrically contracting at L(max) in oxygenated Krebs-Henseleit solution at 28 degrees C. Maximal force generation in response to a premature stimulus was determined at each rate by scanning the coupling interval between paced beats. Under baseline conditions, diaphragmatic muscle contracted faster than atrial and ventricular muscle. In all tissues, maximum potentiation (increase in force above baseline) was approximately 100% of baseline force, and peak potentiation occurred at shorter coupling intervals with increasing rates of stimulation. Single and paired pacing of diaphragm potentiated the contraction during which the extrastimuli were introduced, while in cardiac muscle, extrastimuli potentiated the contraction following the extrastimulus. The maximum potentiated response occurred when the extrastimulus was introduced prior to the development of peak force in diaphragmatic muscle. In contrast, in atrial and ventricular muscle, a single or paired premature stimulus potentiated the subsequent beat when delivered late during relaxation. In cardiac muscle, maximal potentiation gradually occurred following several repetitive stimuli. Following cessation of single and paired pacing, the beat following the potentiated response immediately returned to baseline in diaphragmatic muscle, while a gradual decline was evident over several subsequent beats in cardiac muscle. Increasing the bath temperature from 28 to 37 degrees C resulted in a leftward shift in the peak potentiated force vs. coupling interval curve without a decline in the magnitude of potentiated force in diaphragmatic muscle. In diaphragm muscle, exposure to ryanodine markedly decreased baseline force and maximal potentiation. We conclude that closely timed extrastimuli applied to diaphragmatic muscle can potentiate developed force in a given contraction, while in cardiac tissue a delayed stimulus potentiates the subsequent beat. These differences in contractile responsiveness are not due to differences in loading conditions, but appear to reflect intrinsic differences in calcium handling.     

Enhancement of whole body glucose uptake during and after human skeletal muscle low-frequency electrical stimulation.

There is considerable evidence to suggest that electrical stimulation (ES) activates glucose uptake in rodent skeletal muscle. It is, however, unknown whether ES can lead to similar metabolic enhancement in humans. We employed low-frequency ES through surface electrodes placed over motor points of quadriceps femoris muscles. In male subjects lying in the supine position, the highest oxygen uptake was obtained by a stimulation pattern with 0.2-ms biphasic square pulses at 20 Hz and a 1-s on-off duty cycle. Oxygen uptake was increased by approximately twofold throughout the 20-min stimulation period and returned to baseline immediately after stimulation. Concurrent elevation of the respiratory exchange ratio and blood lactate concentration indicated anaerobic glycogen breakdown and utilization during ES. Whole body glucose uptake determined by the glucose disposal rate during euglycemic clamp was acutely increased by 2.5 mg. kg(-1). min(-1) in response to ES and, moreover, remained elevated by 3-4 mg. kg(-1). min(-1) for at least 90 min after cessation of stimulation. Thus the stimulatory effect of ES on whole body glucose uptake persisted not only during, but also after, stimulation. Low-frequency ES may become a useful therapeutic approach to activate energy and glucose metabolism in humans.     

Measuring muscle and joint geometry parameters of a shoulder for modeling purposes.

An extensive set of muscle and joint geometry parameters was measured of the right shoulder of an embalmed male. For all muscles the optimal muscle fiber length was determined by laser diffraction measurements of sarcomere length. In addition, tendon length and physiological cross-sectional area were determined. The parameter set was needed to enhance the reliability of a computer model of the shoulder (Van der Helm, 1994a,b Journal of Biomechanics 27, 527-550, 551-569). With the model, an abduction of the arm was simulated in seven positions, at 30 degrees intervals. In each of the simulated arm positions, actual sarcomere lengths were calculated from the lengths of 104 muscle elements, distributed over 16 shoulder muscles. For most muscle elements, the simulated abduction appeared to take place within the sarcomere length range in which the muscle elements can exert force. The muscle elements can then act on the ascending limb as well as on the plateau and on the descending limb of the relative force-length curves of sarcomeres. The produced data set is not only important for the refinement of shoulder modeling, but also for functional analyses of shoulder movements in general.     

Ankle muscle coactivation and its relationship with ankle joint kinematics and kinetics during gait in hemiplegic patients after stroke

Introduction: Increased ankle muscle coactivation during gait is a compensation strategy for enhancing postural stability in patients after stroke. However, no previous studies have demonstrated that increased ankle muscle coactivation influenced ankle joint movements during gait in patients after stroke.

Purpose: To investigate the relationship between ankle muscle coactivation and ankle joint movements in hemiplegic patients after stroke.

Methods: Seventeen patients after stroke participated. The coactivation index (CoI) at the ankle joint was calculated separately for the first and second double support (DS1 and DS2, respectively) and single support (SS) phases on the paretic and non-paretic sides during gait using surface electromyography. Simultaneously, three-dimensional motion analysis was performed to measure the peak values of the ankle joint angle, moment, and power in the sagittal plane. Ground reaction forces (GRFs) of the anterior and posterior components and centers of pressure (COPs) trajectory ranges and velocities were also measured.

Results: The CoI during the SS phase on the paretic side was negatively related to ankle dorsiflexion angle, ankle plantarflexion moment, ankle joint power generation, and COP velocity on the paretic side. Furthermore, the CoI during the DS2 phase on both sides was negatively related to anterior GRF amplitude on each side.

Conclusion: Increased ankle muscle coactivation is related to decreased ankle joint movement during the SS phase on the paretic side to enhance joint stiffness and compensate for stance limb instability, which may be useful for patients who have paretic instability during the stance phase after stroke.     

Blood flow and muscle fatigue in SCI individuals during electrical stimulation.

Our purpose was to measure blood flow and muscle fatigue in chronic, complete, spinal cord-injured (SCI) and able-bodied (AB) individuals during electrical stimulation. Electrical stimulation of the quadriceps muscles was used to elicit similar activated muscle mass. Blood flow was measured in the femoral artery by Doppler ultrasound. Muscle fatigue was significantly greater (three- to eightfold, P < or = 0.001) in the SCI vs. the AB individuals. The magnitude of blood flow was not significantly different between groups. A prolonged half-time to peak blood flow at the beginning of exercise (fivefold, P = 0.001) and recovery of blood flow at the end of exercise (threefold, P = 0.009) was found in the SCI vs. the AB group. In conclusion, the magnitude of the muscle blood flow to electrical stimulation was not associated with increased muscle fatigue in SCI individuals. However, the prolonged time to peak blood flow may be an explanation for increased fatigue in SCI individuals.     

Mechanical properties of rabbit latissimus dorsi muscle after stretch and/or electrical stimulation

James, R. S., V. M. Cox, I. S. Young, J. D. Altringham, andD. F. Goldspink Mechanical properties of rabbit latissimus dorsimuscle after stretch and/or electrical stimulation.J. Appl. Physiol. 83(2): 398-406, 1997.The work loop technique was used to measure the mechanicalperformance in situ of the latissimus dorsi (LD) muscles of rabbitsmaintained under fentanyl anesthesia. After 3 wk of incrementallyapplied stretch the LD muscles were 36% heavier, but absolute poweroutput (195 mW/muscle) was not significantly changed relative to thatof external control muscle (206 mW). In contrast, continuous 10-Hzelectrical stimulation reduced power output per kilogram of muscle>75% after 3 or 6 wk and muscle mass by 32% after 6 wk. Whencombined, stretch and 10-Hz electrical stimulation preserved orincreased the mass of the treated muscles but failed to prevent an 80%loss in maximum muscle power. However, this combined treatmentincreased fatigue resistance to a greater degree than electricalstimulation alone. These stretched/stimulated muscles, therefore, aremore suitable for cardiomyoplasty. Nonetheless, further work will benecessary to find an ideal training program for this surgicalprocedure.

     

Influence of electrical stimulation on a fast-twitch muscle in aging rats.

Recently we observed that the flexor digitorum longus muscle of the Fischer 344 rat, which is comprised primarily of type IIb muscle, does not change in size, fiber type, or physiological characteristics during senescence [Am. J. Physiol. 258 (Cell Physiol. 27): C1031-C1035, 1990]. This muscle was utilized to determine whether a predominantly fast-twitch glycolytic muscle would respond to tonic electrical stimulation (ES) with the same degree of fiber-type transformation in aging and young rats. The extent of transformation was quantified by measuring the contractile and metabolic properties, as well as the fiber-type composition, of the flexor digitorum longus muscle after ES (10 Hz, 8 h/day) imposed on the tibial nerve for periods of 0-90 days in young adult (YG; 6-8 mo), middle-aged (MA; 16-18 mo), and senescent (SN; 26-28 mo) male Fischer 344 rats. Although ES induced a IIb-to-IIa fiber-type shift in all groups, in the SN rats the shift was significantly less pronounced at the intermediate time points and remained incomplete after 90 days, compared with YG and MA rats. ES resulted in a reduction in tetanic tension (Po), which in the YG and MA rats was due to a reduction in muscle cross-sectional area. In the SN rats the reduced Po was due to a combined loss of cross-sectional area and specific tension (Po, N/cm2). Contraction and half-relaxation times were largely unaffected by ES, and maximal velocity of unloaded shortening declined throughout ES in all groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of electrical stimulation on the morphological and metabolic properties of paralyzed muscle.

Selected morphological and metabolic properties of single fibers were studied in biopsy samples from the tibialis anterior of normal control and spinal cord-injured (SCI) subjects. In the SCI subjects, one muscle was electrically stimulated progressively over 24 wk, in 6-wk blocks for less than or equal to 8 h/day, while the contralateral muscle remained untreated. The percentage of fibers classified as type I [qualitative alkaline preincubation myofibrillar adenosinetriphosphatase (ATPase)] was significantly less in the unstimulated paralyzed muscles than in the muscles of normal control subjects. Electrical stimulation increased the proportion of type I fibers in the SCI subjects. For both type I and type II fibers, the cross-sectional area, activities of myofibrillar ATPase and succinate dehydrogenase, and the capillary-to-fiber ratio were also significantly less in the paralyzed muscles than in the normal control muscles. Electrical stimulation increased only the activity of succinate dehydrogenase in both fiber types of the SCI subjects. These data are discussed in relation to the electromechanical properties of the respective muscles described in an accompanying paper (J. Appl. Physiol. 72: 1393-1400, 1992). In general, the electrical stimulation protocol used in this study enhanced the oxidative capacity and endurance properties of the paralyzed muscles but had no effect on fiber size and strength.     

Reduced scapular muscle control and impaired shoulder joint position sense in subjects with chronic shoulder stiffness

The purpose of the present study was to determine (1) if joint position sense (JPS) in subjects with shoulder stiffness (SS) differs from that in controls; (2) if, when JPS is reduced in SS, it is related to scapular muscular activities in the mid/end ranges of motion; and (3) if a person’s function is associated with his or her level of JPS. Eighteen subjects with unilateral SS and 18 controls were included. Each subject performed abduction by self-selecting an end/mid range position. The electromagnetic motion-capturing system collected kinematic data while surface electromyography collected muscle activities (upper trapezius, lower trapezius, and serratus anterior muscles). Subjects were asked to move the upper limb to the target position (end/mid range) accurately without visual guidance. Reduced JPS was observed in subjects with SS (2.7 degrees in mid range, p < 0.05). The JPS was enhanced by an increased scapula muscular activation level in the end range of motion (R = ?0.61 for SS and ?0.41 for controls) and by coordination among muscles’ activation in the mid-range of motion (R = ?0.87 for SS and R = ?0.53 for controls). Impaired JPS was also related to self-reported functional status (R = ?0.56) in subjects with SS. Shoulder JPS in subjects with chronic SS is impaired in comparison with controls. In the mid-range motion, the coordination of scapula muscular activation is related to shoulder JPS. Impaired JPS is also function-related in subjects with SS. These findings suggest that the coordination among scapula muscles’ activation were important to consider in the rehabilitation of patients with chronic SS.     

Reduction of muscle fatigue in man by cyclical stimulation

In order to develop a control system for electrical stimulation of paralysed muscle and improve muscle resistance to fatigue, it is useful to investigate the possibilities of simulating the control systems of the normal body. One way is the periodic shifting of stimulation from one muscle to another. This technique is called sequential stimulation and allows sufficient rest time for each muscle to reduce fatigue and consequently prolong muscle strength. It can also be seen to improve the muscle recovery time. In the following study, the muscles rectus femoris, vastus lateralis and vastus medialis were used to keep the knee locked and extended during stimulation. Several experiments were carried out using a three-channel computer controlled stimulator. The results for three-phase sequential stimulation (33% duty cycle per muscle) were most effective and significantly improved the muscle fatigue characteristics.     

Fatigue and non-fatigue mathematical muscle models during functional electrical stimulation of paralyzed muscle

Electrical muscle stimulation demonstrates potential for preventing muscle atrophy and restoring functional movement after spinal cord injury (SCI). Control systems used to optimize delivery of electrical stimulation protocols depend upon the algorithms generated using computational models of paralyzed muscle force output. The Hill–Huxley-type model, while being highly accurate, is also very complex, making it difficult for real-time implementation. In this paper, we propose a Wiener–Hammerstein system to model the paralyzed skeletal muscle under electrical stimulus conditions. The proposed model has substantial advantages in identification algorithm analysis and implementation including computational complexity and convergence, which enable it to be used in real-time model implementation. Experimental data sets from the soleus muscles of 14 subjects with SCI were collected and tested. The simulation results show that the proposed model outperforms the Hill–Huxley-type model not only in peak force prediction, but also in fitting performance for force output of each individual stimulation train.