Influence of Neck Pain, Cervical Extensor Muscle Fatigue, and Manual Therapy on Wrist Proprioception.

OBJECTIVE: The purpose of this study was to examine the effects of submaximal isometric neck muscle fatigue and manual therapy on wrist joint position sense (JPS) within healthy individuals and individuals with subclinical neck pain (SCNP). METHODS: Twelve healthy participants and 12 participants with SCNP were recruited. Each group completed 2 sessions, with 48 hours between sessions. On day 1, both groups performed 2 wrist JPS tests using a robotic device. The tests were separated by a submaximal isometric fatigue protocol for the cervical extensor muscles (CEM). On day 2, both groups performed a wrist JPS test, followed by a cervical treatment consisting of manual therapy (SCNP) or neck rest (20 minutes, control group) and another wrist JPS test. Joint position sense was measured as the participant's ability to recreate a previously presented wrist angle. Each wrist JPS test included 12 targets, 6 into wrist flexion and 6 into wrist extension. Kinematic data from the robot established absolute, variability, and constant error. RESULTS: Absolute error significantly decreased (P = .01) from baseline to post-fatigue in the SCNP group (baseline = 4.48 ± 1.58°; post-fatigue = 3.90 ± 1.45°) and increased in the control group (baseline = 3.12 ± 0.98°; post-fatigue = 3.81 ± 0.90°). The single session of manual cervical treatment significantly decreased absolute error in participants with SCNP (P = .004). CONCLUSION: This study demonstrated that neck pain or fatigue can lead to altered afferent input to the central nervous system and can affect wrist JPS. Our findings demonstrate that acute wrist proprioception may be improved in individuals with SCNP by a single cervical manual therapy session.

The effects of isometric hand grip force on wrist kinematics and forearm muscle activity during radial and ulnar wrist joint perturbations.

The purpose of this work was to investigate forearm muscle activity and wrist angular displacement during radial and ulnar wrist perturbations across various isometric hand grip demands. Surface electromyography (EMG) was recorded from eight muscles of the upper extremity. A robotic device delivered perturbations to the hand in the radial and ulnar directions across four pre-perturbation grip magnitudes. Angular displacement and time to peak displacement following perturbations were evaluated. Muscle activity was evaluated pre- and post-perturbation. Results showed an inverse relationship between grip force and angular displacement (p ≤ 0.001). Time to peak displacement decreased as grip force increased (p ≤ 0.001). There was an increase in muscle activity with higher grip forces across all muscles both pre-and post-perturbation (p ≤ 0.001) and a greater average muscle activity in ulnar as compared to radial deviation (p = 0.02). This work contributes to the wrist joint stiffness literature by relating wrist angular displacement to grip demands during novel radial/ulnar perturbations and provides insight into neuromuscular control strategies.

Effects of Hemispheric Stroke Localization on the Reorganization of Arm Movements within Different Mechanical Environments.

This study investigated how stroke's hemispheric localization affects motor performance, spinal maps and muscle synergies while performing planar reaching with and without assistive or resistive forces. A lesion of the right hemisphere affected performance, reducing average speed and smoothness and augmenting lateral deviation in both arms. Instead, a lesion of the left hemisphere affected the aiming error, impairing the feedforward control of the ipsilesional arm. The structure of the muscle synergies had alterations dependent on the lesion side in both arms. The applied force fields reduced the differences in performance and in muscle activations between arms and among populations. These results support the hypotheses of hemispheric specialization in movement control and identify potential significant biomarkers for the design of more effective and personalized rehabilitation protocols.

Sustained Isometric Wrist Flexion and Extension Maximal Voluntary Contractions Similarly Impair Hand-Tracking Accuracy in Young Adults Using a Wrist Robot.

Due to their stabilizing role, the wrist extensor muscles demonstrate an earlier onset of performance fatigability and may impair movement accuracy more than the wrist flexors. However, minimal fatigue research has been conducted at the wrist. Thus, the purpose of this study was to examine how sustained isometric contractions of the wrist extensors/flexors influence hand-tracking accuracy. While gripping the handle of a three-degrees-of-freedom wrist manipulandum, 12 male participants tracked a 2:3 Lissajous curve (±32° wrist flexion/extension; ±18° radial/ulnar deviation). A blue, circular target moved about the trajectory and participants tracked the target with a yellow circle (corresponding to the handle's position). Five baseline tracking trials were performed prior to the fatiguing task. Participants then exerted either maximal wrist extension or flexion force (performed on separate days) against a force transducer until they were unable to maintain 25% of their pre-fatigue maximal voluntary contraction (MVC). Participants then performed 7 tracking trials from immediately post-fatigue to 10 min after. Performance fatigability was assessed using various metrics to account for errors in position-tracking, error tendencies, and movement smoothness. While there were no differences in tracking error between flexion/extension sessions, tracking error significantly increased immediately post-fatigue (Baseline: 1.40 ± 0.54°, Post-fatigue: 2.02 ± 0.51°, P < 0.05). However, error rapidly recovered, with no differences in error from baseline after 1-min post-fatigue. These findings demonstrate that sustained isometric extension/flexion contractions similarly impair tracking accuracy of the hand. This work serves as an important step to future research into workplace health and preventing injuries of the distal upper-limb.

Dynamic Wrist Flexion and Extension Fatigue Induced via Submaximal Contractions Similarly Impairs Hand Tracking Accuracy in Young Adult Males and Females.

We evaluated the effects of muscle fatigue on hand-tracking performance in young adults. Differences were quantified between wrist flexion and extension fatigability, and between males and females. Participants were evaluated on their ability to trace a pattern using a 3-degrees-of-freedom robotic manipulandum before (baseline) and after (0, 1, 2, 4, 6, 8, and 10 mins) a submaximal-intensity fatigue protocol performed to exhaustion that isolated the wrist flexors or extensors on separate days. Tracking tasks were performed at all time points, while maximal voluntary contractions (MVCs) were performed at baseline, and 2, 6-, and 10-mins post-task termination. We evaluated movement smoothness (jerk ratio, JR), shape reproduction (figural error, FE), and target tracking accuracy (tracking error, TE). MVC force was significantly lower in females (p < 0.05), lower than baseline for all timepoints after task termination (p < 0.05), with no muscle group-dependent differences. JR did not return to baseline until 10-mins post-task termination (most affected), while FE returned at 4-mins post-task termination, and TE at 1-min post-task termination. Males tracked the target with significantly lower JR (p < 0.05), less TE (p < 0.05), and less FE (p < 0.05) than females. No muscle group-dependent changes in hand-tracking performance were observed. Based on this work, hand tracking accuracy is similarly impaired following repetitive submaximal dynamic wrist flexion or extension. The differences between male and female fatigability was independent of the changes in our tracking metrics.

Characterizing forearm muscle activity in university-aged males during dynamic radial-ulnar deviation of the wrist using a wrist robot.

Functioning as wrist stabilizers, the wrist extensor muscles exhibit higher levels of muscle activity than the flexors in most distal upper-limb tasks. However, this finding has been derived mostly from isometric or wrist flexion-extension protocols, with little consideration for wrist dynamics or radial-ulnar wrist deviations. The purpose of this study was to assess forearm muscle activity during the execution of dynamic wrist radial-ulnar deviation in various forearm orientations (pronation/supination). In 12 healthy university-aged males, surface electromyography (EMG) was recorded from eight muscles of the dominant arm: flexor carpi radialis (FCR), flexor carpi ulnaris (FCU), flexor digitorum superficialis (FDS), extensor carpi radialis (ECR), extensor carpi ulnaris (ECU), extensor digitorum (ED), biceps brachii (BB) and triceps brachii (TB). While grasping a handle, participants performed dynamic radial-ulnar deviation using a three-degrees-of-freedom wrist manipulandum. The robotic device applied torque to the handle, in either a radial or ulnar direction, and in one of three forearm postures (30° supinated/neutral/30° pronated). Results indicated that forearm posture influenced the muscles acting upon the hand (FDS/ED), whereas movement phase (concentric-eccentric) and torque direction influenced nearly every muscle. The ECR demonstrated the greatest task-dependency of all forearm muscles, which is possibly reflective of forearm muscle lines of action. Co-contraction ratios were much higher in radial trials than ulnar (Radial: 1.20 ± 0.78, Ulnar: 0.28 ± 0.18, P < 0.05), suggesting greater FCU and ECU contribution to wrist joint stability in radial-ulnar movement. These findings highlight a greater complexity of wrist extensor function than has previously been reported in isometric work.

Characterizing forearm muscle activity in young adults during dynamic wrist flexion-extension movement using a wrist robot.

Current research suggests that the wrist extensor muscles function as the primary stabilizers of the wrist-joint complex. However, most investigations have utilized isometric study designs, with little consideration for wrist dynamics or changes in posture. The purpose of the present study was to assess forearm muscle activity during the execution of dynamic wrist flexion/extension in multiple forearm orientations (pronation/supination). In 12 young adult males, surface electromyography (EMG) was recorded from eight muscles of the dominant arm: flexor carpi radialis (FCR), flexor carpi ulnaris (FCU), flexor digitorum superficialis (FDS), extensor carpi radialis (ECR), extensor carpi ulnaris (ECU), extensor digitorum (ED), biceps brachii (BB) and triceps brachii (TB). While grasping a handle, participants performed dynamic wrist flexion/extension using a three-degrees-of-freedom wrist manipulandum. The robotic device applied torque to the handle, in either a flexion or extension direction, and in one of three forearm postures (30° supinated/neutral/30° pronated). Results indicated that forearm posture had minimal influence on forearm muscle activity, but significantly altered the activity of the biceps and triceps brachii. Movement phase (concentric-eccentric) dictated muscle activity in every muscle. Interestingly, muscle activity in the eccentric phase was equal between the two applied handle torques, regardless of whether the muscle acted as the agonist or antagonist. Co-contraction ratios were higher in the flexion conditions (flexion: 2.28 ± 2.04, extension: 0.32 ± 0.27), suggesting significantly greater wrist extensor activity-likely a contribution to wrist joint stability. This highlights the vulnerability of the wrist extensor muscles to overuse injuries in settings requiring prolonged use of dynamic wrist exertions.

Coupling Robot-Aided Assessment and Surface Electromyography (sEMG) to Evaluate the Effect of Muscle Fatigue on Wrist Position Sense in the Flexion-Extension Plane.

Proprioception is a crucial sensory modality involved in the control and regulation of coordinated movements and in motor learning. However, the extent to which proprioceptive acuity is influenced by local muscle fatigue is obscured by methodological differences in proprioceptive and fatiguing protocols. In this study, we used high resolution kinematic measurements provided by a robotic device, as well as both frequency and time domain analysis of signals captured via surface electromyography (sEMG) to examine the effects of local muscle fatigue on wrist proprioceptive acuity in 16 physically and neurologically healthy young adults. To this end, participants performed a flexion/extension ipsilateral joint position matching test (JPM), after which a high-resistive robotic task was used to induce muscle fatigue of the flexor carpi radialis (FCR) muscle. The JPM test was then repeated in order to analyze potential changes in proprioceptive acuity. Results indicated that the fatigue protocol had a significant effect on movements performed in flexion direction, with participants exhibiting a tendency to undershoot the target before the fatigue protocol (-1.218°), but overshooting after the fatigue protocol (0.587°). In contrast, in the extension direction error bias values were similar before and after the fatigue protocol as expected (pre = -1.852°, post = -1.237°) and reflected a tendency to undershoot the target. Moreover, statistical analysis indicated that movement variability was not influenced by the fatigue protocol or movement direction. In sum, results of the present study demonstrate that an individual's estimation of wrist joint displacement (i.e., error bias), but not precision (i.e., variability), is affected by muscular fatigue in a sample of neurologically and physically healthy adults.

Muscle fatigue assessment during robot-mediated movements.

BACKGROUND: Several neuromuscular disorders present muscle fatigue as a typical symptom. Therefore, a reliable method of fatigue assessment may be crucial for understanding how specific disease features evolve over time and for developing effective rehabilitation strategies. Unfortunately, despite its importance, a standardized, reliable and objective method for fatigue measurement is lacking in clinical practice and this work investigates a practical solution. METHODS: 40 healthy young adults performed a haptic reaching task, while holding a robotic manipulandum. Subjects were required to perform wrist flexion and extension movements in a resistive visco-elastic force field, as many times as possible, until the measured muscles (mainly flexor and extensor carpi radialis) exhibited signs of fatigue. In order to analyze the behavior and the characteristics of the two muscles, subjects were divided into two groups: in the first group, the resistive force was applied by the robot only during flexion movements, whereas, in the second group, the force was applied only during extension movements. Surface electromyographic signals (sEMG) of both flexor and extensor carpi radialis were acquired. A novel indicator to define the Onset of Fatigue (OF) was proposed and evaluated from the Mean Frequency of the sEMG signal. Furthermore, as measure of the subjects' effort throughout the task, the energy consumption was estimated. RESULTS: From the beginning to the end of the task, as expected, all the subjects showed a decrement in Mean Frequency of the muscle involved in movements resisting the force. For the OF indicator, subjects were consistent in terms of timing of fatigue; moreover, extensor and flexor muscles presented similar OF times. The metabolic analysis showed a very low level of energy consumption and, from the behavioral point of view, the test was well tolerated by the subjects. CONCLUSION: The robot-aided assessment test proposed in this study, proved to be an easy to administer, fast and reliable method for objectively measuring muscular fatigue in a healthy population. This work developed a framework for an evaluation that can be deployed in a clinical practice with patients presenting neuromuscular disorders. Considering the low metabolic demand, the requested effort would likely be well tolerated by clinical populations.

A novel method for muscle fatigue assessment during robot-based tracking tasks.

In this work we propose a novel method based on sEMG signals, easy and fast to perform, administered with a robotic device to maximize repeatability and objectivity. Muscle fatigue, which is frequently experienced by healthy subjects, can be a highly debilitating symptom in case of neuromuscular disorders. Its assessment provides crucial information on the progression of the disability itself, on patient's muscular function and on the efficacy of the eventual clinical intervention. Hence, a robust and objective protocol for fatigue assessment is fundamental in rehabilitation practice. Therefore, the aim of this work was twofold. Firstly, we aimed to test the proposed method and highlight its strengths and drawbacks for a future optimization and implementation in a clinical context. Secondly, we meant to identify which are the most sensitive and reliable measures of muscles' performance that can quickly and optimally predict subjects' behavior. sEMG signals were collected from right Extensor and Flexor Carpi Radialis of 9 healthy subjects during a flexion-extension robotic task consisting in a haptic tracking in a viscous field. Three indicators of fatigue (Mean Frequency, Dimitrov Index, Root Mean Square) were obtained and we proposed a novel sensitive parameter which determines the Onset of Fatigue.