Alterations in muscle activation patterns during robotic-assisted walking

Twelve patients with cervical dystonia (CD) and predominant rotation were studied to determine the effects of changes in head posture on the specific patterns of cervical muscle activity. Turns analysis was used to quantify muscle activity underlying head rotation, recorded simultaneously from the agonist and antagonist muscle pairs bilaterally (sternocleidomastoid [SCM] and splenius [SPL]). Muscle activity was compared between the uncompensated dystonic posture and during the maintenance of midposition. In addition, patients were separated into two groups (geste = 6; no geste = 6) based on whether they had a clinically efficacious geste to determine the effect of geste on patterns of cervical muscle activity. Muscle activity was measured during the maintenance of midposition with and without a clinical or simulated geste. Differences in muscle activity between the groups and postures were compared using repeated measure analysis of variance (ANOVA) analyses. The four muscles tested showed a significant difference in muscle activity in the uncompensated dystonic posture as a result of the increased activity in the agonist muscle pair (SCM and SPL responsible for the dystonic posture) (EMG amplitude: F[1,11] = 18.81, p = 0.0012; EMG frequency: F[1,11] = 32.07, p = 0.0001). Maintaining the head in the midposition was associated with a significant reduction in muscle activity compared with the uncompensated dystonic posture (EMG amplitude: F[1,9] = 6.36, p < 0.033; EMG frequency: F[1,9] = 10.96, p < 0.0091). This reduction in midposition muscle activity was significantly greater in the agonist muscle pair (EMG amplitude: F[1,10] = 19.70, p = 0.0013; EMG frequency: F[1,10] = 44.67, p < 0.0001). In the patients with clinically effective geste, there was no additional reduction in muscle activity observed in the midposition when they performed their geste (EMG amplitude: F[1,9] = 4.63, p = 0.060; EMG frequency: F[1,9] = 1.22, p = 0.298). These findings suggest that CD with rotation is characterized by predominantly increased agonist muscle activation. Patients with CD retain the ability to modulate this involuntary agonist muscle activity to maintain the head in the midposition. The maintenance of the midposition does not seem to be facilitated by geste.

Purpose/Hypothesis: Body weight supported treadmill training (BWSTT) has been shown to be effective in retraining walking following incomplete spinal cord injury (SCI), although its performance in the clinic is limited. Development of robotic devices which provide passive guidance during walking may increase performance of BWSTT, but may minimize voluntary effort by the subject. The purpose of this study was to investigate whether robotic-assisted treadmill walking provides a sufficient stimulus to generate appropriate muscle activity and metabolic responses compared to therapist-assisted walking. We hypothesized that therapist-assisted treadmill walking would generate increased Vo2 responses and more appropriate lower extremity muscle activity vs., robotic-assisted treadmill walking. Number of Subjects: Twelve individuals with motor incomplete SCI participated in the study. Materials/Methods: Cardiopulmonary, metabolic, and electromyographic (EMG) responses during therapist-assisted treadmill walking were compared to robotic-assisted ambulation with and without visual biofeedback. Robotic training was provided by the Lokomat and visual feedback of bilateral hip and knee torques during swing and stance phases were displayed on a computer screen. Subjects were asked to walk on the treadmill with <40% BWS for 10 minutes with either robotic- or therapist-assistance followed by 10 minutes of the other testing method. Standardized metabolic testing equipment was used to obtain cardiopul-monary measurements for 5 minutes in sitting and 2 minutes in standing prior to treadmill walking and throughout the testing period including 10 minutes of recovery. Electromyographic (EMG) activity was collected from key lower extremity muscles during each minute of treadmill walking. Results: Therapist-assisted treadmill walking demonstrated significantly higher (p < 0.01) Vo2, heart rate (HR), and minute ventilation (VE) during all 10 minutes compared with robotic-assisted walking without biofeedback. Providing visual biofeedback during the walking tasks minimized the differences between conditions, although Vo2 responses during therapist-assisted walking were greater (p < 0.05) during the last 3 minutes of walking. EMG activity was significantly higher only for the rectus femoris in pre-swing during therapist- vs. robotic-assisted walking without feedback. This difference was minimized with feedback. Conclusions: Therapist-assisted treadmill walking elicits increased aerobic responses and more appropriate muscle activity compared to robotic-assisted treadmill walking, although provision of biofeedback of joint torques may increase patient effort. Clinical Relevance: Understanding the physiological responses to robotic- or therapist-assisted BWSTT is important the relative contribution of passive guidance during walking tasks.

Association Between Knee Joint Muscle Activation and Knee Joint Moment Patterns During Walking in Moderate Medial Compartment Knee Osteoarthritis: Implications for Secondary Prevention

Assessing muscle activation and monitoring stroke recovery progress are vital aspects of evaluating motor impairment. Surface electromyography, a common tool for measuring muscle activity, has practical limitations for clinical implementation and fails to capture deep muscle activities, leading to challenges in accurately identifying muscle activation patterns in stroke patients. To address these limitations, we introduce an All Muscle Activity Test and Evaluation (AMATE) system, combining wearable sensor technology with a musculoskeletal model. AMATE computes activation levels of all lower limb muscles during various activities without requiring surface electrodes. It also generates an Activation Dissimilarity Index (ADI) to illustrate muscle activation patterns among individuals. We evaluated AMATE's effectiveness through a pilot study involving 22 walking trials with healthy subjects and stroke patients. The results highlight AMATE's capability in aiding clinicians to analyze and understand diverse lower limb muscle activation patterns in stroke patients, particularly identifying muscles with abnormal activation for targeted rehabilitative training.

Medical Equipment to Make Colonoscopy Procedures Safer for Physicians: Control Head Holder and Splatter Shield1

Healthy individuals modulate muscle activation patterns according to their intended movement and external environment. Persons with neurological disorders (e.g., stroke and spinal cord injury), however, have problems in movement control due primarily to their inability to modulate their muscle activation pattern in an appropriate manner. A functionality test at the level of individual muscles that investigates the activity of a muscle of interest on various motor tasks may enable muscle-level force grading. To date there is no extant work that focuses on the application of exoskeleton robots to induce specific muscle activation in a systematic manner. This paper proposes a new method, named "individual muscle-force control" using a wearable robot (an exoskeleton robot, or a power-assisting device) to obtain a wider variety of muscle activity data than standard motor tasks, e.g., pushing a handle by hand. A computational algorithm systematically computes control commands to a wearable robot so that a desired muscle activation pattern for target muscle forces is induced. It also computes an adequate amount and direction of a force that a subject needs to exert against a handle by his/her hand. This individual muscle control method enables users (e.g., therapists) to efficiently conduct neuromuscular function tests on target muscles by arbitrarily inducing muscle activation patterns. This paper presents a basic concept, mathematical formulation, and solution of the individual muscle-force control and its implementation to a muscle control system with an exoskeleton-type robot for upper extremity. Simulation and experimental results in healthy individuals justify the use of an exoskeleton robot for future muscle function testing in terms of the variety of muscle activity data.

Robot-assisted walking with the Lokomat: The influence of different levels of guidance force on thorax and pelvis kinematics

Overground vs. treadmill walking on biomechanical energy harvesting: An energetics and EMG study

Human grip is commonly used in sport and recreational activities and involves the coordinated activation of forearm muscles. Lateral epicondylalgia (LE) is a common musculoskeletal disorder that involves pathology of the tendon of extensor carpi radialis brevis (ECRB) at its insertion onto the lateral epicondyle of the humerus. LE presents clinically as pain provoked by gripping activities and has a major impact on function. This results in days off work and time off sport. Despite considerable research into the pathophysiology of LE, it remains poorly understood whether forearm muscles activity is altered during gripping in individuals with LE. This thesis aimed to comprehensively understand the extent of current knowledge and provide new data of activity of the wrist/forearm muscles in LE. Study 1 clarifies the current understanding of muscle activity in LE by way of systematic review with quantitative analysis. This review identified that studies of individuals with LE revealed altered motor unit morphology, abnormal patterns of muscle activity during resisted wrist extension and tennis strokes, fewer cortical peaks and less distance between cortical representation of muscles (mapped with transcranial magnetic stimulation), and delayed activation of wrist extensor muscles during gripping, when contrasted to pain-free controls. The latter finding was also present on the asymptomatic limb. Importantly, this systematic review identified limited understanding of gripping despite the clinical importance of this task in provocation of LE. The only study that had investigated muscle activity during this task had severe limitations that compromise the interpretation of the results. Limitations included the use of surface electromyography (which does not record from individual muscles), and performance of sustained contraction with high grip force (50% maximum voluntary contraction), which is likely to be provocative of pain in some individuals with LE. On the basis of some evidence of sensorimotor changes in the asymptomatic limb of individuals with unilateral LE, Study 2 was conducted as a systematic review with meta-analysis to determine the extent bilateral differences in sensorimotor function between individuals with unilateral tendinopathy and pain-free controls. Study 2 identified evidence for several sensory and motor system differences, and evidence for tendon pathology in the asymptomatic limb of individuals with other unilateral tendinopathies (Achilles tendinopathy) but not LE when contrasted to pain-free controls. On the foundation that tendon pathology was present in asymptomatic limb of individuals with Achilles tendinopathy, Study 3 investigated whether there was a greater prevalence of tendon pathology of the asymptomatic common extensor tendon of individuals with LE than pain-free controls. Unlike the findings in the Achilles tendon, Study 3 did not identify greater tendon pathology in the asymptomatic limb of individuals with unilateral LE than that present in the tendons of pain-free individuals. As no studies had explored specific muscle activation during a low level grip, Study 4 compared the contribution of forearm muscle activity to gripping between the symptomatic and asymptomatic sides in individuals with unilateral LE and pain-free individuals. This study highlighted altered muscle activity in LE characterised by a lower contribution of ECRB in the symptomatic arm and a greater contribution of extensor digitorum communis (EDC) and flexor digitorum profundus (FDP) to total EMG bilaterally, in individuals with LE than pain-free individuals. Modified distribution of activity between the synergist wrist extensor muscles ECRB and EDC has potential to impact on the functional performance of grip. The strategy used by individuals with might compromise efficient grip as finger flexor muscles (FDP) would need to overcome finger extensor muscle activity (EDC). Although potentially negative for grip, the different motor pattern could have consequences for ECRB pathology by unloading the muscle. This could provide a benefit of pain reduction, but also potential negative effects from stress shielding of the tendon. Study 5 investigated potential differences in muscle synergies (defined as groups of muscles working together to simplify central nervous system processing) between individuals with LE and pain-free individuals. For both groups, analysis with non-negative matrix factorization identified two muscle synergies involved in control of forearm muscles during repetitive gripping. Comparison between groups indicated the variance accounted for by the muscle synergies was lower in the LE group than pain-free individuals, which suggests more variation in muscle activation pattern for that group. The studies outlined in this thesis identified differences in the control of forearm muscles between individuals with and without LE. The findings imply that EDC provides a greater contribution and ECRB a lesser contribution to the gripping task in individuals with LE than pain-free controls. Given the cross-sectional study design it is not possible to clarify whether the differences preceded or followed LE, but in both cases rehabilitation of muscle activation is likely to be beneficial for recovery. Clinical interventions to modify forearm muscle activity may provide clinical benefit, but future research is needed to determine whether altered muscle activity can be changed and whether this improves outcomes.

Effects of a robotic end-effector device on muscle patterns while walking under different levels of assistance

Muscle activity pattern dependent pain development and alleviation

The aim of the present study was to clarify the effect of electrical muscle stimulation (EMS) on the spatial distribution pattern of electromyographic activity in healthy young adults using multi-channel surface electromyography (SEMG). A total of 32 men (age = 21–26 years) were randomly assigned to the intervention group (n = 18) and control group (n = 14). Participants in the intervention group performed EMS to stimulate the bilateral lower limb muscle for four weeks (20 min/3 days/week). The control group received no EMS intervention. To understand the effects of EMS, the following measurements were made at baseline and four weeks: knee extension torque, muscle mass, and spatial distribution of neuromuscular activation during a target torques [10%, 30%, 50%, and 70% of the maximal voluntary contraction (MVC)] using multi-channel SEMG. The knee extension torque was significantly increased in intervention group compared with control group (p < 0.0001). However, the muscle mass did not show a significant difference between pre and post intervention in each group. The muscle activation patterns of 50% and 70% MVC task showed significant enhancement between baseline and four weeks in the intervention group. Furthermore, a moderate correlation between Δ knee extension torque and Δ spatial distribution pattern of electromyographic activity of 50% and 70% MVC in the intervention group was observed. These results suggested EMS intervention induced different distribution of muscle activity at high-intensity muscle contraction compared with low-intensity muscle contraction.

The Lokomat is a commercially available exoskeleton for gait training in persons with cerebral palsy (CP). Because active contributions and variability over movement repetitions are determinants of training effectiveness, we studied muscle activity in children with CP, and determined (i) differences between treadmill and Lokomat walking, and (ii) the effects of Lokomat training parameters, on the amplitude and the stride-to-stride variability. Ten children with CP (age 13.2±2.9, GMFCS level II(n=6)/III(n=4)) walked on a treadmill (±1km/h; 0% bodyweight support(BWS)), and in the Lokomat (50% and 100% guidance; ±1km/h and ±2km/h; 0% and 50% BWS). Activity was recorded from Gluteus Medius (GM), Vastus Lateralis (VL), Biceps Femoris (BF), Medial Gastrocnemius (MG) and Tibialis Anterior (TA) of the most affected side. The averaged amplitude per gait phase, and the second order coefficient of variation was used to determine the active contribution and stride-to-stride variability, respectively. Generally, the amplitude of activity was lower in the Lokomat than on the treadmill. During Lokomat walking, providing guidance and BWS resulted in slightly lower amplitudes whereas increased speed was associated with higher amplitudes. No significant differences in stride-to-stride variability were observed between Lokomat and treadmill walking, and in the Lokomat only speed (MG) and guidance (BF) affected variability. Lokomat walking reduces muscle activity in children with CP, whereas altering guidance or BWS generally does not affect amplitude. This urges additional measures to encourage active patient contributions, e.g. by increasing speed or through instruction.

BackgroundAltered knee muscle activity in children with asymptomatic Generalized Joint Hypermobility (GJH) is reported during isometric contraction, static and dynamic balance tasks and jumping, but has not been studied during gait. Therefore, the aim was to investigate group differences in knee muscle activity simultaneously with knee joint kinematics during treadmill walking between children with and without GJH.MethodsGirls 14–15 years of age with GJH (inclusion criteria: Beighton score ≥6 of 9 and positive hyperextension ≥10° (one/both knees)) and a matched control group without GJH (inclusion criteria: Beighton score ≤5 and no knee hyperextension ≥10° ) were recruited. In total 16 participants with GJH and 10 non-GJH participants were included in the study.Surface electromyography (sEMG) was measured from the quadriceps, hamstrings and gastrocnemius muscles of the dominant leg during treadmill walking. Maximal voluntary isometric contractions while sitting were used for normalisation of sEMG to % of Maximum Voluntary EMG (%MVE). Knee joint angles during treadmill walking were measured by electrogoniometer. Furthermore, co-contraction index (CCI) was calculated, and presented for muscle groups of hamstrings-quadriceps (HQ) and gastrocnemius-quadriceps (GQ). CCI of medial and lateral sides of the knee, including ratio of the medial and lateral CCI for HQ and GQ were calculated.ResultsNo group differences were found in demographics, muscle activation level, nor CCI and CCI ratios. However, participants with GJH displayed significantly decreased knee joint angle, mean (153º vs. 156º; p =0.03) and minimum (105º vs. 111º; p=0.01), during treadmill walking compared with controls.ConclusionMuscle activity during gait was not different between participants with GJH and non-GJH participants. However, participants with GJH displayed minor but statistically significant increased knee flexion during gait. Since the clinical consequences of increased knee joint flexion during gait are unknown, future studies should follow a larger cohort longitudinally during overground walking for development of clinical complications in this group.

To characterize how infants with myelomeningocele (MMC) activate lower limb muscles over the first year of life, without practice, while stepping on a motorized treadmill. Twelve infants with MMC were tested longitudinally at 1, 6, and 12 months. Electromyography was used to collect data from the tibialis anterior, lateral gastrocnemius, rectus femoris, biceps femoris. Across the first year, infants showed no electromyographic activity for approximately 50% of the stride cycle with poor rhythmicity and timing of muscles, when activated. Single muscle activation predominated; agonist-antagonist coactivation was low. Probability of individual muscle activity across the stride decreased with age. Infants with MMC show high variability in timing and duration of muscle activity, few complex combinations, and very little change over time.