A Study on sEMG-Based Motor Variability and Functional Connectivity of the Upper Limb Depending on Weight Distributions in a Handle of a Cordless Stick-Type Vacuum Cleaner.

This study investigated the muscle activities, motor variability, and functional connectivity of the upper limb as a function of weight distributions in a handle of a cordless stick-type vacuum cleaner. Eighteen female college students with experience of vacuum cleaner-use participated in testing. Five handles with different centers of mass (CM) were prepared (centroid, top-rear, top-front, bottom-front, and bottom-rear), and electromyography for the muscles of the upper limb were measured during vacuuming. The results showed that the %MVC values of the Extensor Carpi Ulnaris (p = 0.0038) and Deltoid Middle (p = 0.0094) increased but that of the Biceps Brachii (p = 0.0001) decreased, as the CM moved from the top to bottom area of the handle. The motor variability of the Extensor Carpi Ulnaris (p = 0.0335) and Brachioradialis (p = 0.0394) significantly varied depending on the CM locations but failed to show significance in the post-hoc analyses. Lastly, the functional connectivity values of the muscle pairs such as the Extensor Carpi Ulnaris-Deltoid Middle (p = 0.0016), Extensor Carpi Ulnaris-Upper Trapezius (p = 0.0174), Brachioradialis-Biceps Brachii (p = 0.0356), and Biceps Brachii-Upper Trapezius (p = 0.0102) were significantly altered as a function of the CM locations. The lowest functional connectivity was found with the handle of which CM was at centroid.

Cervical Spine Motion During Vehicle Extrication of Healthy Volunteers.

Objective: Prehospital spinal motion restriction as a prevention technique for secondary neurological injury is a key principle in emergency medicine. Our aim was to evaluate the effectiveness of different cervical spinal cord motion restriction techniques of awake and cooperative healthy volunteers during extrication.Methods: Twenty-three healthy volunteers were asked to exit a car (unassisted) with a rigid cervical collar (CC condition) or without it (autonomous exit: AE; instructed exit: IE); they were also extricated by two rescuers after setting a rigid cervical collar and by using an extrication device (CC + XT condition). Eight 3 D infrared cameras were calibrated around the vehicle to measure cervical spine angle, angular speed and acceleration in the sagittal plane. Surface wireless EMG electrodes were used to record superior trapezius, erector spinae and rectus abdominis muscle activity. All measures were recorded during two phases: device positioning (maneuver) and vehicle exiting.Results: The lowest range of motion was observed in CC during maneuver and exit (about 17°), the greatest in AE and IE (about 45°); when the extrication device was utilized along with the cervical collar (CC + XT) an increase, rather than a further decrease, in the range of motion was observed (about 25° during maneuver and exit). Larger values of angular speed and acceleration were observed in CC + XT when compared to CC, both during maneuver and exit (p < 0.001). The lowest EMG activity was observed during maneuver in CC and CC + XT; during exit a lower EMG activity was observed in CC + XT compared to CC (p < 0.001). Thus, when an extrication device is utilized (CC + XT), a lower active control of the cervical spine region is associated with faster and more brisk movements of the cervical spine compared to CC alone.Conclusions: Our findings support the idea that spinal motion restriction via rigid cervical collar of awake and cooperative trauma patients is effective in reducing cervical spine motion in the sagittal plane during vehicle extrication.

Limitations of Spectral Electromyogramic Analysis to Determine the Onset of Neuromuscular Fatigue Threshold during Incremental Ergometer Cycling.

Recently, a new method has been proposed to detect the onset of neuromuscular fatigue during an incremental cycling test by assessing the changes in spectral electromyographic (sEMG) frequencies within individual exercise periods of the test. The method consists on determining the highest power output that can be sustained without a significant decrease in spectral frequencies. This study evaluated the validity of the new approach by assessing the changes in spectral indicators both throughout the whole test and within individual exercise periods of the test. Fourteen cyclists performed incremental cycle ergometer rides to exhaustion with bipolar surface EMG signals recorded from the vastus lateralis. The mean and median frequencies (Fmean and Fmedian, respectively) of the sEMG power spectrum were calculated. The main findings were: (1) Examination of spectral indicators within individual exercise periods of the test showed that neither Fmean nor Fmedian decreased significantly during the last (most fatiguing) exercise periods. (2) Examination of the whole incremental test showed that the behaviour of Fmean and Fmedian with increasing power output was highly inconsistent and varied greatly among subjects. (3) Over the whole incremental test, half of the participants exhibited a positive relation between spectral indicators and workload, whereas the other half demonstrated the opposite behavior. Collectively, these findings indicate that spectral sEMG indexes do not provide a reliable measure of the fatigue state of the muscle during an incremental cycling test. Moreover, it is concluded that it is not possible to determine the onset of neuromuscular fatigue during an incremental cycling test by examining spectral indicators within individual exercise periods of the test. Key pointsThe behaviour of spectral EMG indicators during the incremental test exhibited a high heterogeneity among individuals, with approximately half of the participants showing a positive relation between spectral indicators and workload and the other half showing the opposite behaviour.None of the spectral EMG indicators examined (Fmean nor Fmedian) decreased significantly between the ventilatory threshold and the highest power output.Examination of spectral indicators within individual exercise periods of the test showed that neither Fmean nor Fmedian decreased significantly during the last (most fatiguing) exercise periods.

Dominant and Nondominant Leg Kinematics During Kicking in Young Soccer Players: A Cross-Sectional Study.

The goal of the study is to analyze the kinematics and provide an EMG analysis of the support limb during an instep kick in adolescent players. We set a video camera, two torque transducers on the knee, and EMG sensors. A sample of 16 adolescent soccer players between 10 and 12 years old performed kicks. The kinematics shows a p = .039 on frontal plane (dominant 15.4 ± 1.8, nondominant 18.8 ± 1.7); the EMG analysis shows a p = .04 on muscular activation timing for the vastus medialis. A difference between the legs on the frontal plane emerges. Moreover, a huge difference on sagittal plane between the adolescent pattern and adult pattern exists (15° in adolescent population, 40° in adult population). The result shows a greater activation of the vastus medialis in the nondominant leg; probably, in this immature pattern, the adolescents use this muscle more than necessary.

Biomechanical Effects of Adding an Ankle Soft Actuation in a Unilateral Exoskeleton.

Stroke disease leads to a partial or complete disability affecting muscle strength and functional mobility. Early rehabilitation sessions might induce neuroplasticity and restore the affected function or structure of the patients. Robotic rehabilitation minimizes the burden on therapists by providing repetitive and regularly monitored therapies. Commercial exoskeletons have been found to assist hip and knee motion. For instance, unilateral exoskeletons have the potential to become an effective training system for patients with hemiparesis. However, these robotic devices leave the ankle joint unassisted, essential in gait for body propulsion and weight-bearing. This article evaluates the effects of the robotic ankle orthosis T-FLEX during cooperative assistance with the AGoRA unilateral lower-limb exoskeleton (hip and knee actuation). This study involves nine subjects, measuring muscle activity and gait parameters such as stance and swing times. The results showed a reduction in muscle activity in the Biceps Femoris of 50%, Lateral Gastrocnemius of 59% and Tibialis Anterior of 35% when adding T-FLEX to the AGoRA unilateral lower-limb exoskeleton. No differences were found in gait parameters. Nevertheless, stability is preserved when comparing the two legs. Future works should focus on evaluating the devices in ground tests in healthy subjects and pathological patients.

Genioglossal response to mechanical vibrations of the mandible and the submandibular muscles.

The extrinsic tongue muscles are activated in coordination with pharyngeal muscles to dilate the airways as needed during breathing. The genioglossus (GG) activity is known to be modulated by several reflexes evoked via the mechanoreceptors of the upper airways. The primary objective of this paper was to investigate the effectiveness of activating these reflex pathways using mechanical stimulation of the mandible or the submandibular muscles. In eight healthy subjects, 3-s long, 5-mm vertical mechanical vibrations were delivered at 8 and 12 Hz to the lower jaw in a seated position, while the GG EMG was recorded using a custom-made sublingual electrode, along with the activity of the masseter (MS) and mylohyoid (MH). All three muscle activities were significantly higher during stimulation compared with the baseline (P < 0.02), and the increase was larger at 12 Hz versus 8 Hz (P < 0.02). All three muscle responses had components that synchronized with the mechanical stimuli, but those of MS were much more strongly phase-locked to the vibrational cycle. In 10 healthy subjects, we also applied mechanical vibrations to the submandibular muscles at three different stimulation intensities, while subjects were lying in a supine position. The GG activity increased significantly above the baseline (P = 0.026) in 9 out of 10 subjects, and the elevated activity persisted after termination of the stimulus for a few seconds. The results demonstrate that GG muscle responses can be evoked with mechanical vibrations applied to the lower jaw or the submandibular muscles in healthy subjects during wakefulness. NEW & NOTEWORTHY The evoked responses observed in the genioglossus (GG) activity during mechanical vibrations of the lower jaw or the submandibular muscles may lead to therapeutic applications for improving the patency of airways during sleep. The presence of these GG reflexes may also explain a mechanism by which the vibrations produced during snoring can help the airways stay open in individuals who may otherwise have obstructed airways in sleep.

[Electromyography Analysis of Rapid Eye Movement Sleep Behavior Disorder].

Polysomnography (PSG), which records physiological phenomena including brain waves, breathing status, and muscle tonus, is useful for the diagnosis of sleep disorders as a gold standard. However, measurement and analysis are complex for several specific sleep disorders, such as rapid eye movement (REM) sleep behavior disorder (RBD). Usually, brain waves during REM sleep indicate an awakening pattern under relaxed conditions of skeletal and antigravity muscles. However, these muscles are activated during REM sleep when patients suffer from RBD. These activated muscle movements during REM, so-called REM without atonia (RWA) recorded by PSG, may be related to a neurodegenerative disease such as Parkinson's disease. Thus, careful analysis of RWA is significant not only physically, but also clinically. Commonly, manual viewing measurement analysis of RWA is time-consuming. Therefore, quantitative studies on RWA are rarely reported. A software program, developed from Microsoft Office Excel®, was used to semiautomatically analyze the RWA ratio extracted from PSG to compare with manual viewing measurement analysis. In addition, a quantitative muscle tonus study was carried out to evaluate the effect of medication on RBD patients. Using this new software program, we were able to analyze RWA on the same cases in approximately 15 min as compared with 60 min in the manual viewing measurement analysis. This software program can not only quantify RWA easily but also identify RWA waves for either phasic or tonic bursts. We consider that this software program will support physicians and scientists in their future research on RBD. We are planning to offer this software program for free to physicians and scientists.

Night-to-night variability of automatic quantitative parameters of the chin EMG amplitude (Atonia Index) in REM sleep behavior disorder.

STUDY OBJECTIVES: To analyze the night-to-night variability of REM sleep electromyographic (EMG) features of REM sleep behavior disorder (RBD) by using the automatic quantitative method known as atonia index (AI), and to evaluate the improvement in sensitivity and specificity of AI for the diagnosis of RBD when a second recording night is available. SETTING: Sleep research center. INTERVENTIONS: N/A. METHODS: A group of 17 idiopathic RBD patients was recruited for whom 2 all-night polysomnographic (PSG) recordings were available. Thirty normal controls were also recruited and subgrouped into Young (< 45 years of age) or Aged (> 45 years). Chin EMG analysis was run on all recordings; night-to-night variability of both AI and number of chin EMG activations/h during REM sleep was additionally quantified as the absolute difference between the 2 nights standardized as the percentage of their mean. MEASUREMENTS AND RESULTS: Night-to-night variability of AI was higher in RBD patients (19.7%) than in the 2 groups of controls (Young 1.8% and Aged 2.8%). The values of variability of chin EMG activations were much higher than those of AI, especially in the Aged controls. Sensitivity of AI ≤ 0.9 for RBD was always higher than 82% and reached 88.9% for the combined-night analysis; specificity was also high, with a value of 92.3% for the combined-value analysis. CONCLUSION: The night-to-night variability of AI seems to be very low in normal controls and remains under 20% in RBD patients; that of the number of EMG activations is higher. However, even a single PSG recording provides high values of sensitivity and specificity when a threshold value of AI ≤ 0.9 is used to define abnormal chin EMG levels during REM sleep that increase only moderately when a second night recording is available.