Antagonist Muscles Research Articles

Directed network analysis reveals changes in cortical and muscular connectivity caused by different standing balance tasks

Objective. Standing balance forms the basis of daily activities that require the integration of multi-sensory information and coordination of multi-muscle activation. Previous studies have confirmed that the cortex is directly involved in balance control, but little is known about the neural mechanisms of cortical integration and muscle coordination in maintaining standing balance. Approach. We used a direct directed transfer function (dDTF) to analyze the changes in the cortex and muscle connections of healthy subjects (15 subjects: 13 male and 2 female) corresponding to different standing balance tasks. Main results. The results show that the topology of the EEG brain network and muscle network changes significantly as the difficulty of the balancing tasks increases. For muscle networks, the connection analysis shows that the connection of antagonistic muscle pairs plays a major role in the task. For EEG brain networks, graph theory-based analysis shows that the clustering coefficient increases significantly, and the characteristic path length decreases significantly with increasing task difficulty. We also found that cortex-to-muscle connections increased with the difficulty of the task and were significantly stronger than the muscle-to-cortex connections. Significance. These results show that changes in the difficulty of balancing tasks alter EEG brain networks and muscle networks, and an analysis based on the directed network can provide rich information for exploring the neural mechanisms of balance control.

Necrobotics: Biotic Materials as Ready-to-Use Actuators.

Designs perfected through evolution have informed bioinspired animal‐like robots that mimic the locomotion of cheetahs and the compliance of jellyfish; biohybrid robots go a step further by incorporating living materials directly into engineered systems. Bioinspiration and biohybridization have led to new, exciting research, but humans have relied on biotic materials—non‐living materials derived from living organisms—since their early ancestors wore animal hides as clothing and used bones for tools. In this work, an inanimate spider is repurposed as a ready‐to‐use actuator requiring only a single facile fabrication step, initiating the area of “necrobotics” in which biotic materials are used as robotic components. The unique walking mechanism of spiders—relying on hydraulic pressure rather than antagonistic muscle pairs to extend their legs—results in a necrobotic gripper that naturally resides in its closed state and can be opened by applying pressure. The necrobotic gripper is capable of grasping objects with irregular geometries and up to 130% of its own mass. Furthermore, the gripper can serve as a handheld device and innately camouflages in outdoor environments. Necrobotics can be further extended to incorporate biotic materials derived from other creatures with similar hydraulic mechanisms for locomotion and articulation.

The effects of lower extremity static muscle fatigue on balance components

BackgroundThe body exhibits dynamic and static movements in response to the changes in the center of gravity in some positions. Balance plays a key role in all sports branches and daily life because it can control the lowest energy consumption and muscle activation.ObjectivesThis study investigated the effects of lower extremity static muscle fatigue on static and dynamic balance components.Design/methodsThe sample consisted of 40 healthy volunteers aged 18–24 years. Participants took part in an isometric fatigue protocol for lower extremity muscles. A squat position was used for static fatigue for lower extremity muscles. Measurements were performed in a squat press for 25 s, with the knee at a 90-degree angle and a load of about 30% of the participant's weight isometrically. The protocol was repeated five times. The participant was allowed to rest for two minutes between each repetition. The muscles and their antagonists that contracted most actively during the squat press exercise were vastus lateralis obliquus, rectus femoris, tibialis anterior, biceps femoris, semi tendineus, and lateral gastrocnemius. Electromyography (EMG) measurements were conducted on these muscles bilaterally and motion analysis system was used to standardize the 90-degree angle of the knee joint.ResultsThere was a significant difference between pre-test and post-test Eyes Open (EO) static balance scores, pre- and post-exercise post-test dynamic balance scores between non-athletes and athletes, pre- and post-exercise post-test dominant leg EO, and pre-test non-dominant leg between non-athletes and athletes (p < .05). There was a significant difference in the Median Frequency (MF) (Hz) values of the dominant leg agonist rectus femoris (p < .05) and the antagonist muscle semi tendineus (p < .05) scores during isometric squat press between athletes and non-athletes.ConclusionsWe need different applications to understand the mechanisms underlying balance and discover athletes' potential. Lower extremity proprioception exercises have positive effects on static body balance parameters.

Dynamics and Computed-Muscle-Force Control of a Planar Muscle-Driven Snake Robot

This paper presents the dynamic formulation of an artificial-muscle-driven and computed-muscle–force control for the planar locomotion of a snake robot. The snake robot uses a series of antagonistic pneumatic artificial muscles, assembled at the joints, to generate the locomotion. Kinematics of the artificial-muscle-driven robot in the joint and Cartesian spaces was derived with respect to the muscles’ motion. The Lagrangian mechanics was employed for the formulation of the dynamic model of the robot and deriving the equations of motion. A model-based computed-muscle-force control was designed to track the desired paths/trajectories in Cartesian space. The feedback linearization method based on a change of coordinate was utilized to determine an equivalent linear (input-to-state) system. Then, a full state feedback control law was designed, which satisfies the stability and tracking problems. The performance of the dynamic model and the controller were successfully demonstrated in simulation studies for tracking a circle-shape path and a square-shape path with a constant linear velocity while generating the lateral undulation gait. The results indicate a low magnitude of tracking errors where the controlled muscle force are bounded to the actual pneumatic artificial muscle’s limitations.

Practical value and thought on "co-regulation of body and mind" in treatment of post-stroke spasticity with acupuncture

This paper reviews the application of "co-regulation of body and mind" of acupuncture for post-stroke spasticity. It is found that acupoints on the head and the back of the governor vessel, as well as Jiaji (Ex-B 2) points are mainly used for regulating the mind, and the local sites of spastic muscles and the points on the antagonistic muscles are for regulating the body specially. It is believed that regulating the mind should be integrated with regulating the body, while, the acupoint selection be associated with needling methods so as to fully achieve the "co-regulation of body and mind" and enhance the practical value of acupuncture for post-stroke spasticity. It is proposed that the classical anti-spastic needling techniques, such as huici (relaxing needling) and guanci (joint needling), should be more considered.

Effect of Electrical Stimulation (ES) Combined with Conventional Therapy on Spasticity, Function and Ambulation for patients with stroke: Protocol for a Randomized Control Trial

Background: Spasticity is a motor symptom which is responsible for impairments as it decreases range of movement, postural abnormality, poor hygiene, inability to perform daily activities. Since the 1960s, electrical stimulation (FES) has been used to treat chronic hemiplegic patients. It is a physical therapeutic approach that improves spasticity by agonist muscle relaxation or antagonist muscle strengthening. This study aims to evaluate the effect of electrical stimulation along with conventional therapy and conventional therapy alone on spasticity, function and ambulation of the individuals suffering from Stroke. Method and analysis: The study will be a multicenter, Randomized Control Trial (RCT). Stroke survivors with spasticity in any limbs who will attend in the neurology unit of 24 selected rehabilitation centers including Center for the Rehabilitation of the Paralysed (CRP) Savar and Mirpur Dhaka, Bangladesh from July 2022 to February 2023, will be considered as study population. Hospital based randomization processes will be employed. To receive either conventional intervention or EFS along with conventional , participants will be randomly assigned into [1:1] groups. Concealed allocation will be executed by computer generated randomization and will be done by another person who is not involved in the trial. Primary outcome spasticity will be evaluated by modified Asworth grading scale and modified Tardieu scale; function by Barthel Index and ambulation by 10 meter walk test. Secondary outcome upper extremity muscle strength will be evaluated by motricity index and lower limb function by lower extremity functional scale (LEFS). Conclusion: FES with conventional therapy will add new knowledge to manage stroke patients. Reduction of spasticity and improvement of function will reduce the burden of stroke patients as well as their families. Hopefully this research will update the rehabilitation process of stroke patients in Bangladesh.

Optimization of Seating Position and Stimulation Pattern in Functional Electrical Stimulation Cycling: Simulation Study.

Two significant challenges facing functional electrical stimulation (FES) cycling are the low power output and early onset of muscle fatigue, mainly due to the non-physiological and superficial recruitment of motor units and weakness of the antagonistic muscles. Thus optimization of the cycling biomechanical properties and stimulation pattern to achieve maximum output power with minimum applied electrical stimulus is of great importance. To find the optimal seating position and stimulation pattern, the previous works either ignored the muscle's force-velocity and force-length properties or employed complicated muscle models which was a massive barrier to clinical experiments. In this work, an easy-to-use and precise muscle model in conjunction with Jacobian-based torque transfer functions were adopted to determine the optimal seating position, trunk angle, crank arm length, and stimulation intervals. Furthermore, the impact of muscle force-velocity factor in finding the optimal seating position and stimulation intervals was investigated. The simulation models showed the trivial effect of the force-velocity factor on the resulting optimal seating position of six healthy simulated subjects. This method can enhance the FES-cycling performance and shorten the time-consuming process of muscle model identification for optimization purposes.

Antagonistic Control of a Cable-Driven Prosthetic Hand with Neuromorphic Model of Muscle Reflex.

In this paper, a novel prototype of a cable-driven prosthetic hand with biorealisitic muscle property was developed. A pair of antagonistic muscles controlled the flexion and extension of the prosthetic index finger. Biorealistic properties of muscle were emulated using a neuromorphic model of muscle reflex in real time. The model output was coupled to a servo motor that tracked the computed muscle force. The servo motor was able to track model output within a frequency range from 0 to 8.29 (Hz) with a phase shift from 2 to 205 (deg). Surface electromyography signals collected from the amputee's forearm were used as α commands to drive the muscle model. With this prototype system, we evaluated its characteristics for force and stiffness control. Results of the force variability test showed that the standard deviation of fingertip force was linear to the mean fingertip force, indicating that force variability was proportional to the background force. At different levels of antagonistic co-contraction, the index finger and muscles displayed different levels of stiffness corresponding to the degree of co-activation. This prototype system showed the similar compliant behaviors of human limbs actuated with biological muscles. In further studies, this prototype system would be thoroughly evaluated for its biorealistic properties, and integrated with sensors to investigate feedback strategies of various sensory information for individuals with amputation. Clinical Relevance- This article established an antagonistic control of a cable-driven prosthetic hand with biorealistic properties of muscle reflex for application to individuals with amputation.

Effects of laser therapy and Grimaldi’s muscle shortening maneuver on spasticity in central nervous system injuries

Background an Aims: For 2003 year until today we treated hundreds of patients with Central Nervous System Injuries (CNSI), using Non-Surgical Laser Therapy (NSLT) obtaining good results in terms of sensibility and movement. In order to increase muscle strength and to further explore new emerging synergies, we have also started using a physical therapy practice based on the most current knowledge about the motor control, called Grimaldi’s Muscle Shortening Maneuver (GMSM). Spasticity is often the most disabling symptom and the current therapies are still not able to heal it at all. The goal of our study is to suggest a new way of treatment of spasticity, supporting it with objective measurements of muscle thresholds. Materials and Methods: In 2016-2017, 36 patients with traumatic or degenerative CNSI were enrolled. Lasers used were 808 nm, 10600 nm, and 1064 nm, applied with a first cycle of 20 sessions, four a day. Patients were subjected to Grimaldi’s Muscle Shortening Maneuver (MSM) twice a day, ten sessions at all, working selectively on hypertonic muscles and their antagonists. Before treatment, tonic stretch reflex thresholds (TSRTs) in Gastrocnemius Lateralis (GL) were assessed through a surface electromyography (sEMG) device paired with an electrogoniometer. Antagonist muscle force (Tibialis Anterioris) was assessed by some electronic hand-held dynamometers. For the clinical measure, we used the Modified Ashworth Scale (MAS). All tests have been performed at the baseline (before starting treatments), after one week (at the end of the last treatment) and after a month. Results: Results were considered positive if the instrumental assessment procedure showed modifications in TSRT values and subjects improved their antagonist muscle strength. Results showed modifications in TSRT values at every follow up. The average comparison between the follow-ups was always statistically significant (p .000). The increase in Tibialis Anterioris muscle strength was statistically significant as well (p .000). MAS showed some differences between followups but not all of them are statistically significant (T0-T1 p .063, T1-T2 p .001, T0-T2 p .000). Encouraging results suggest a possible correlation between laser and MSM therapies and modifications of TSRT in spastic muscles. Conclusion: Associating laser treatment and Grimaldi’s Muscle Shortening Maneuver (MSM) seems to be effective on spasticity in patients affected by traumatic or degenerative CNSI. Obviously, this kind of study design showed a lot of limits however this clinical series could be an important hint for every researcher working in the complex field of spasticity, a symptom that is poorly defined and hardly treated.

How Does Lower Limb Respond to Unexpected Balance Perturbations? New Insights from Synchronized Human Kinetics, Kinematics, Muscle Electromyography (EMG) and Mechanomyography (MMG) Data.

Making rapid and proper compensatory postural adjustments is vital to prevent falls and fall-related injuries. This study aimed to investigate how, especially how rapidly, the multiple lower-limb muscles and joints would respond to the unexpected standing balance perturbations. Unexpected waist-pull perturbations with small, medium and large magnitudes were delivered to twelve healthy young adults from the anterior, posterior, medial and lateral directions. Electromyographical (EMG) and mechanomyographical (MMG) responses of eight dominant-leg muscles (i.e., hip abductor/adductors, hip flexor/extensor, knee flexor/extensor, and ankle dorsiflexor/plantarflexors) together with the lower-limb joint angle, moment, and power data were recorded. The onset latencies, time to peak, peak values, and/or rate of change of these signals were analyzed. Statistical analysis revealed that: (1) agonist muscles resisting the delivered perturbation had faster activation than the antagonist muscles; (2) ankle muscles showed the largest rate of activation among eight muscles following both anteroposterior and mediolateral perturbations; (3) lower-limb joint moments that complied with the perturbation had faster increase; and (4) larger perturbation magnitude tended to evoke a faster response in muscle activities, but not necessarily in joint kinetics/kinematics. These findings provided insights regarding the underlying mechanism and lower-limb muscle activities to maintain reactive standing balance in healthy young adults.

Assisting Forearm Function in Children With Movement Disorders via A Soft Wearable Robot With Equilibrium-Point Control.

Wearable robots are envisioned to amplify the independence of people with movement impairments by providing daily physical assistance. For portable, comfortable, and safe devices, soft pneumatic-based robots are emerging as a potential solution. However, due to the inherent complexities, including compliance and nonlinear mechanical behavior, feedback control for facilitating human–robot interaction remains a challenge. Herein, we present the design, fabrication, and control architecture of a soft wearable robot that assists in supination and pronation of the forearm. The soft wearable robot integrates an antagonistic pair of pneumatic-based helical actuators to provide active pronation and supination torques. Our main contribution is a bio-inspired equilibrium-point control scheme for integrating proprioceptive feedback and exteroceptive input (e.g., the user’s muscle activation signals) directly with the on/off valve behavior of the soft pneumatic actuators. The proposed human–robot controller is directly inspired by the equilibrium-point hypothesis of motor control, which suggests that voluntary movements arise through shifts in the equilibrium state of the antagonistic muscle pair spanning a joint. We hypothesized that the proposed method would reduce the required effort during dynamic manipulation without affecting the error. In order to evaluate our proposed method, we recruited seven pediatric participants with movement disorders to perform two dynamic interaction tasks with a haptic manipulandum. Each task required the participant to track a sinusoidal trajectory while the haptic manipulandum behaved as a Spring-Dominate system or Inertia-Dominate system. Our results reveal that the soft wearable robot, when active, reduced user effort on average by 14%. This work demonstrates the practical implementation of an equilibrium-point volitional controller for wearable robots and provides a foundational path toward versatile, low-cost, and soft wearable robots.

Motor Unit Recruitment is Altered When Acute Experimental Pain is Induced at a Site Distant to the Contracting Muscle

Acute pain alters motor unit discharge properties in muscles that are painful or influence loading of painful structures. Less is known about the changes in discharge when pain is induced in distant tissues that are unable or have limited capacity to modify the load of the contracting muscle. We aimed to determine whether acute experimental pain alters quadriceps motor unit discharge when pain is induced in; (i) a muscle that is unlikely to be mechanically influenced by modified quadriceps activity (tibialis anterior: TA), or (ii) the antagonist muscle (biceps femoris: BF). Using a within-subject design, 16 adults performed force-matched isometric knee extension during pain-free control conditions, and trials after painful hypertonic saline injections into TA or BF. Surface and intramuscular electromyography recordings were made. Despite maintained force, discharge rate of quadriceps motor units was lower during Pain than Control conditions for TA and BF trials (both P < 0.001). Redistribution of motor unit activity was observed; some units were recruited in control or pain but not both. As modified quadriceps motor unit discharge has limited/no potential to modify load in the painful tissue to protect the painful part, the findings might support an alternative hypothesis that activity is redistributed to larger motor units.

Changes of agonist and synergist muscles activity during a sustained submaximal brake-pulling gesture

We analyzed the time course of changes in muscle activity of the prime mover and synergist muscles during a sustained brake-pulling action and investigated the relationship between muscle activity and braking force fluctuation (FF). Thirty-two participants performed a continuous fatiguing protocol (CFP) at 30% of maximal voluntary contraction (MVC) until failure. Surface electromyography was used to analyze root mean square (RMS) values in the flexor digitorum superficialis (FD), flexor carpi radialis (FC), extensor digitorum communis (ED), extensor carpi radialis (EC), brachioradialis (BR), biceps brachii (BB), and triceps brachii (TB). The FF and RMS in all muscles increased progressively (P<0.01) during the CFP, with sharp increments at time limit particularly in FD and FC (P<0.001). The RMS of the FD and FC were comparable to the baseline MVC values at time limit, in comparison to the other muscles that did not reach such levels of activity (P<0.003). The three flexor/extensor ratios used to measure coactivation levels decreased significantly (P<0.001). In contrast to RMS, MVC was still depressed at the minute 10 of recovery. The results suggest that the time limit was mainly constrained by fatigue-related mechanisms of the FD and FC but not by those of other synergist and antagonist muscles.

Optimal reaching trajectories based on feedforward control.

In human upper-arm reaching movements, the variance of the hand position increases until the middle of the movement and then decreases toward the endpoint. Such decrease in positional variance has been suggested as an evidence to support the hypothesis that our nervous system uses feedback control, rather than feedforward control, for arm reaching tasks. In this study, we computed the optimal trajectories based on feedforward control under several criteria for a one-link two-muscle arm model with considering the stochastic property of muscle activities in order to reexamine the hypothesis. The results showed that the feedforward control also represents the decrease in positional variance in the latter half of the movement when the control signal is planned under the minimum energy cost and minimum variance models. Furthermore, the optimal trajectory that minimizes energy cost represents not only the decrease in positional variance but also many other characteristics of the human reaching movements, e.g., the three-phasic activity of antagonistic muscle, bell-shaped speed curve, N-shaped equilibrium trajectory, and bimodal profile of joint stiffness. These results suggest that minimum energy cost model well expresses the characteristics of hand reaching movements, and our central nervous system would make use of not only a feedback control but also feedforward control.

Comparison of Immediate Effect of Muscle Energy Technique in Upper Trapezius and Activation of its Antagonist Muscle i.e., Middle and Lower Trapezius with Thoracic Extension in Patients with Upper Trapezius Spasm

Comparison of Immediate Effect of Muscle Energy Technique in Upper Trapezius and Activation of its Antagonist Muscle i.e., Middle and Lower Trapezius with Thoracic Extension in Patients with Upper Trapezius Spasm

Upper Limbs Muscle Co-contraction Changes Correlated With the Impairment of the Corticospinal Tract in Stroke Survivors: Preliminary Evidence From Electromyography and Motor-Evoked Potential.

ObjectiveIncreased muscle co-contraction of the agonist and antagonist muscles during voluntary movement is commonly observed in the upper limbs of stroke survivors. Much remain to be understood about the underlying mechanism. The aim of the study is to investigate the correlation between increased muscle co-contraction and the function of the corticospinal tract (CST).MethodsNine stroke survivors and nine age-matched healthy individuals were recruited. All the participants were instructed to perform isometric maximal voluntary contraction (MVC) and horizontal task which consist of sponge grasp, horizontal transportation, and sponge release. We recorded electromyography (EMG) activities from four muscle groups during the MVC test and horizontal task in the upper limbs of stroke survivors. The muscle groups consist of extensor digitorum (ED), flexor digitorum (FD), triceps brachii (TRI), and biceps brachii (BIC). The root mean square (RMS) of EMG was applied to assess the muscle activation during horizontal task. We adopted a co-contraction index (CI) to evaluate the degree of muscle co-contraction. CST function was evaluated by the motor-evoked potential (MEP) parameters, including resting motor threshold, amplitude, latency, and central motor conduction time. We employed correlation analysis to probe the association between CI and MEP parameters.ResultsThe RMS, CI, and MEP parameters on the affected side showed significant difference compared with the unaffected side of stroke survivors and the healthy group. The result of correlation analysis showed that CI was significantly correlated with MEP parameters in stroke survivors.ConclusionThere existed increased muscle co-contraction and impairment in CST functionality on the affected side of stroke survivors. The increased muscle co-contraction was correlated with the impairment of the CST. Intervention that could improve the excitability of the CST may contribute to the recovery of muscle discoordination in the upper limbs of stroke survivors.

Detailed Dynamic Model of Antagonistic PAM System and Its Experimental Validation: Sensorless Angle and Torque Control With UKF

This article proposes a detailed nonlinear mathematical model of an antagonistic pneumatic artificial muscle (PAM) actuator system for estimating the joint angle and torque using an unscented Kalman filter (UKF). The proposed model is described in a hybrid state-space representation. It includes the contraction force of the PAM, joint dynamics, fluid dynamics of compressed air, mass flows of a valve, and friction models. A part of the friction models is modified to obtain a novel form of the Coulomb friction depending on the inner pressure of the PAM. For model validation, offline and online UKF estimations and sensorless tracking control of the joint angle and torque are conducted to evaluate the estimation accuracy and tracking control performance. The estimation error is less than 7.91 %, and the steady-state tracking control performance is more than 94.75 %. These results confirm that the proposed model is detailed and could be used as the state estimator of an antagonistic PAM system.

Stability analysis of multi-serial-link mechanism driven by antagonistic multiarticular artificial muscles

Artificial multiarticular musculoskeletal systems consisting of serially connected links driven by monoarticular and multiarticular muscles, which are often inspired by vertebrates, enable robots to elicit dynamic, elegant, and flexible movements. However, serial links driven by multiarticular muscles can cause unstable motion (e.g., buckling). The stability of musculoskeletal mechanisms driven by antagonistic multiarticular muscles depends on the muscle configuration, origin/insertion of muscles, spring constants of muscles, contracting force of muscles, and other factors. We analyze the stability of a multi-serial-link mechanism driven by antagonistic multiarticular muscles aiming to avoid buckling and other undesired motions. We theoretically derive the potential energy of the system and the stable condition at the target point, and validate the results through dynamic simulations and experiments. This paper presents the static stability criteria of serially linked robots, which are redundantly driven by monoarticular and multiarticular muscles, resulting in the design and control guidelines for those robots.

Brain oscillatory activity correlates with the relief of post-stroke spasticity following focal vibration.

Some evidence has demonstrated that focal vibration (FV) contributes to the relief of post-stroke spasticity (PSS). Although the changes of cortical activity correlating with the relief of PSS induced by FV have been explored using transcranial magnetic stimulation, brain oscillatory activity during the above-mentioned process has not been fully understood. The main purpose of this study is to explore the correlation between the changes in brain oscillatory activity and the relief of PSS following FV. A clinical experiment was carried out, in which FV (87 Hz, 0.28 mm) was applied over the antagonist muscle's belly of the spastic muscle of ten chronic spastic stroke patients. An electroencephalogram was recorded following before-FV and three sessions of FV. Muscle properties to assess the relief of PSS were tested before-FV and immediately after three sessions of FV. EEG analysis has shown that FV can lead to the significant decrease in the relative power at C3 and C4 in the beta1 (13, 18 Hz), as well as C3 and C4 in the beta3 band (21, 30 Hz), indicating the activation of primary sensorimotor cortex (S1-M1). Muscle properties analysis has shown that, in the state of flexion of spastic muscle, muscle compliance and muscle displacement of the spastic muscle significantly increased right after FV, illustrating the relief of the spasticity. Moreover, the increase of muscle compliance is positively correlated with the reduction of difference index of the activation of bilateral S1-M1. This finding indicated that the relief of PSS can be associated with the activation of bilateral S1-M1 where the activation of the ipsilesional S1-M1 was higher than that of the contralesional one. This study showed the brain oscillatory activity in the bilateral S1-M1 correlating with the relief of PSS following FV, which could contribute to establishing cortex oscillatory activity as a biomarker of the relief of PSS and providing a potential mechanism explanation of the relief of PSS.

Comparing Temporospatial Performance During Brisk and Self-Paced Walking by Men With Osteomyoplastic Transfemoral Amputation and Controls Using Pressure and Muscle Activation Peak Times.

BackgroundThe aim of osteomyoplastic transfemoral amputation (OTFA) is to produce sustained, robust prosthetic gait performance by residuum reconstructing. A better understanding of residuum-socket interface pressures (RSI) and residuum muscle activation should uniquely reveal gait stability to better inform long-term rehabilitation goals.ObjectivesThe objectives of this study are to characterize RSI pressures and residuum muscle activation in men with OTFA while walking at two speeds and compare temporospatial muscle activation with intact controls.MethodsIn this study, we observed and compared healthy men with OTFA and controls during 2-min gait trials at brisk and self-paced speeds, two visits, and 1 year apart. RSI pressures and hip adductors, hamstrings, and quadriceps activation were recorded for those with OTFA. OTFA temporospatial muscle activation patterns were compared with the controls. Within the extracted strides, heel-strike and toe-off events and EMG activation peak times were characterized and compared. Peak times for pressure and EMG activity were examined in individual muscles and antagonist muscles of residual and intact limbs.ResultsSix men with OTFA exhibited adductor, hamstring, and quadriceps co-contraction within intact and residual limbs, regardless of walking speed or trial. Co-contraction within their intact limb occurred throughout the gait cycle. Within the residuum, co-contraction occurred during weight transference. The 75% most likely RSI peaks occurred during stance. EMG peaks were 75% most likely to occur during early stance, terminal stance-initial swing, and terminal swing.ConclusionParticipants with OTFA demonstrated adductors-hamstrings-quadriceps co-contraction in the intact thigh and residuum with corresponding RSI pressure increase, primarily during transitions between stance and swing, indicating gait instability, demonstrating the need to explicitly address these deficits continuously in rehabilitation and wellness settings.