Startle Increases the Incidence of Anticipatory Muscle Activations but Does Not Change the Task-Specific Muscle Onset for Patients After Subacute Stroke

Objectives: To demonstrate the task-specificities of anticipatory muscle activations (AMAs) among different forward-reaching tasks and to explore the StartleReact Effect (SE) on AMAs in occurrence proportions, AMA onset latency or amplitude within these tasks in both healthy and stroke population.Methods: Ten healthy and ten stroke subjects were recruited. Participants were asked to complete the three forward-reaching tasks (reaching, reaching to grasp a ball or cup) on the left and right hand, respectively, with two different starting signals (warning-Go, 80 dB and warning-startle, 114 dB). The surface electromyography of anterior deltoid (AD), flexor carpi radialis (FCR), and extensor carpi radialis (ECR) on the moving side was recorded together with signals from bilateral sternocleidomastoid muscles (SCM), lower trapezius (LT), latissimus dorsi (LD), and tibialis anterior (TA). Proportions of valid trials, the incidence of SE, AMA incidence of each muscle, and their onset latency and amplitude were involved in analyses. The differences of these variables across different move sides (healthy, non-paretic, and paretic), normal or startle conditions, and the three tasks were explored. The ECR AMA onset was selected to further explore the SE on the incidence of AMAs.Results: Comparisons between move sides revealed a widespread AMA dysfunction in subacute stroke survivors, which was manifested as lower AMA onset incidence, changed onset latency, and smaller amplitude of AMAs in bilateral muscles. However, a significant effect of different tasks was only observed in AMA onset latency of muscle ECR (F = 3.56, p = 0.03, η2p = 0.011), but the significance disappeared in the subsequent analysis of the stroke subjects only (p > 0.05). Moreover, the following post-hoc comparison indicated significant early AMA onsets of ECR in task cup when comparing with reach (p < 0.01). For different stimuli conditions, a significance was only revealed on shortened premotor reaction time under startle for all participants (F = 60.68, p < 0.001, ηp2 = 0.056). Furthermore, stroke survivors had a significantly lower incidence of SE than healthy subjects under startle (p < 0.01). But all performed a higher incidence of ECR AMA onset (p < 0.05) than with normal signal. In addition, the incidence of ECR AMAs of both non-paretic and paretic sides could be increased significantly via startle (p ≤ 0.02).Conclusions: Healthy people have task-specific AMAs of muscle ECR when they perform forward-reaching tasks with different hand manipulations. However, this task-specific adjustment is lost in subacute stroke survivors. SE can improve the incidence of AMAs for all subjects in the forward-reaching tasks involving precision manipulations, but not change AMA onset latency and amplitude.

The Acute Effect of Accentuated Eccentric Overloading upon the Kinematics and Myoelectric Activity in the Eccentric and Concentric Phase of a Traditional Bench Press

The target of this study was to investigate the acute effect of a supramaximal augmented eccentric load on the kinematics and myoelectric activity during the concentric phase of the lift in a traditional bench press. Ten resistance-trained males (age 24 ± 6.4 years, height 1.80 ± 0.07 m, body-mass 87.2 ± 16.9 kg) performed two repetitions at 110/85% of the 1-RM in the dynamic accentuated external resistance (DAER) group and two repetitions at 85/85% of the 1-RM for the control group in a traditional bench press. The barbell kinematics, joint kinematics and myoelectric activity of eight muscles were measured in the eccentric phase and the pre-sticking, sticking and post-sticking regions. The main findings were that the sticking region started at a lower barbell height and that a lower barbell velocity was observed in the sticking region during the second repetition in the DAER condition compared to the control condition. Additionally, the lateral deltoid muscle and clavicle part of the pectoralis were more active during the eccentric loading compared to the control condition for the second repetition. Furthermore, higher myoelectric activity was measured during the second repetition in the sticking region for the eccentric loading condition in both pectoralis muscles, while the sternal parts of the pectoralis and anterior deltoid were more active during the second repetition of the control condition in the post-sticking region. Based on our findings, it can be concluded that the supramaximal loading in the descending phase with 110% of the 1-RM in the bench press does not have an acute and positive effect of enhanced performance in the ascending phase of the lift at 85% of 1-RM. Instead, fatigue occurs when using this eccentric load during a bench press.

Alternative to Reduced Stresses on the Upper Extremity in a Standing Workstation

Objective This study evaluated a standing armrest to provide more acceptable ergonomic guidelines that may reduce the cost of standing computer workstations. Background Of the many advantages of standing workstations, there have been no efforts to minimize the biomechanical cost, such as larger wrist extension and greater forearm muscle activity than sitting. Method Sixteen participants were asked to perform a typing task under a combination of the following factors: (1) desk shape (rectangular and concave); (2) desk height (0, +5, -5 cm from 90° elbow flexion); and (3) monitor height (0, −10 cm from the eyes). During the trials, the trunk kinematics, muscle activation levels, and CoP were recorded. Results Both arms were further away from the upper body under the concave and +5 desk height than under the normal condition, but significant decreases in the extensor carpi radialis (8.6%), anterior deltoid (28.8%), and L4 paraspinals (5.5%) were observed. Similarly, the wrist extension angle decreased by 10.5° (42%) under this condition, but the posture required a 2.2° (19%) increase in wrist adduction angle. The CoP irregularity was greater under the concave workstation, indicating more complex motion. Conclusion A higher and concave desk can provide an armrest effect while engaged in a standing workstation by reducing the wrist extension and related muscle activation level, but at the cost of a larger wrist adduction angle. Application Providing a standing armrest (+5 cm height and concave desk) could reduce the stresses on the upper extremities, but a split keyboard should be considered to minimize wrist adduction.

Delayed Anticipatory Muscle Activation in Rotator Cuff Tendinopathy

Background: Previous research investigating rotator cuff (RC) tendinopathy has usually focused on pathoanatomy. The pathologic response to anticipatory postural adjustments (APAs) has not yet been investigated. Purpose/Hypothesis: To explore changes in APAs as detected by pre-emptive activation of shoulder muscles during ball catching. It was hypothesized that anticipatory muscle activation (AMA) would be present in the unaffected shoulder but delayed or absent in the affected shoulder in patients with RC tendinopathy. Study Design: Controlled laboratory study. Methods: This study included 21 RC tendinopathy patients with a mean age of 49.5 years. Patients were required to grab a ball embedded with an electromyography sensor when it dropped on their hand, and surface electromyography signals were recorded from the infraspinatus, upper trapezius, anterior deltoid, and biceps. The trials utilized 2 balls, weighing 200 g and 500 g. Each ball was used in 2 trials, 1 involving a number count preceding the ball drop (predictable) and the other involving a sudden drop (unpredictable). The onsets of AMA between the affected and unaffected limbs were compared. Results: Regardless of the experimental condition, significantly delayed AMA onsets were identified in all investigated muscles of the affected side compared with those of the unaffected side, except for the biceps muscle in the 500-g predictable trial. For the infraspinatus, the mean onset time in the 200-g predictable trial was –141.0 ± 60.2 ms on the affected side and –211.9 ± 67.1 ms on the unaffected side ( P < .001); in the 200-g unpredictable trial this value was –139.5 ± 54.9 ms on the affected side and –199.5 ± 56.2 ms on the unaffected side ( P < .001). Conclusion: Delayed AMA was observed in the affected shoulder compared with the unaffected shoulder in patients with RC tendinopathy, not only in the RC muscle but also in the periscapular and upper arm muscles. This may indicate that central hypoexcitability is partly responsible. Clinical Relevance: The basis for RC tendinopathy treatment should not be limited to the tendon pathoanatomy. Delayed AMA around the shoulder joint could provide insight into potential mechanisms related to the central nervous system.

The Effect of Grip Width on Muscle Strength and Electromyographic Activity in Bench Press among Novice- and Resistance-Trained Men

Background: This study compared the muscle activity and six repetition maximum (6-RM) loads in bench press with narrow, medium, and wide grip widths with sub-group comparisons of resistance-trained (RT) and novice-trained (NT) men. Methods: After two familiarization sessions, twenty-eight subjects lifted their 6-RM loads with the different grip widths with measurement of electromyographic activity. Results: Biceps brachii activity increased with increasing grip width, whereas wide grip displayed lower triceps brachii activation than medium and narrow. In the anterior deltoid, greater activity was observed using a medium compared to narrow grip. Similar muscle activities were observed between the grip widths for the other muscles. For the RT group, greater biceps brachii activity with increasing grip width was observed, but only greater activity was observed in the NT group between narrow and wide. Comparing wide and medium grip width, the RT group showed lower triceps activation using a wide grip, whereas the NT group showed lower anterior deltoid activation using a narrow compared to medium grip. Both groups demonstrated lower 6-RM loads using a narrow grip compared to the other grips. Conclusion: Grip widths affect both 6-RM loads and triceps brachii, biceps brachii, and anterior deltoid activity especially between wide and narrow grip widths.

Accessibility and Thickness of Medial and Lateral Talar Body Cartilage for Treatment of Ankle and Foot Osteochondral Lesions

Background: The purposes of this study were to determine (1) if cartilage thicknesses on the talar dome and medial/lateral surfaces of the talus were similar, (2) whether there was sufficient donor cartilage surface area on the medial and lateral talar surfaces to repair talar dome cartilage injuries of the talus, and (3) whether the cartilage surface could be increased following anterior talofibular ligament (ATFL) and sectioning of the tibionavicular and tibiospring portion of the anterior deltoid. Methods: Medial and lateral approaches were utilized in 8 cadaveric ankles to identify the accessible medial, lateral, and talar dome cartilage surfaces in 3 conditions: (1) intact, (2) ATFL release, and (3) superficial anterior deltoid ligament release. The talus was explanted, and the cartilage areas were digitized with a coordinate measuring machine. Cartilage thickness was quantified using a laser scanner. Results: The mean cartilage thickness was 1.0 ± 0.1 mm in all areas tested. In intact ankles, the medial side of the talus showed a larger total area of available cartilage than the lateral side (152 mm2 vs 133 mm2). ATFL release increased the available cartilage area on the medial and lateral sides to 167 mm2 and 194 mm2, respectively. However, only the lateral talar surface had sufficient circular graft donor cartilage available for autologous osteochondral transplantation (AOT) procedures of the talus. After ATFL and deltoid sectioning, there was an increase in available graft donor cartilage available for AOT procedures. Conclusion: The thickness of the medial and lateral talar cartilage surfaces is very similar to that of the talar dome cartilage surface, which provides evidence that the medial and lateral surfaces may serve as acceptable AOT donor cartilage. The surface area available for AOT donor site grafting was sufficient in the intact state; however, sectioning the ATFL and superficial anterior deltoid ligament increased the overall lateral talar surface area available for circular grafting for an AOT procedure that requires a larger graft. These results support the idea that lateral surfaces of the talus may be used as donor cartilage for an AOT procedure since donor and recipient sites are similar in cartilage thickness, and there is sufficient cartilage surface area available for common lesion sizes in the foot and ankle. Clinical Relevance: This anatomical study investigates the feasibility of talar osteochondral autografts from the medial or lateral talar surfaces exposed with standard approaches. It confirms the similar cartilage thickness of the talar dome and the ability to access up to an 8- to 10-mm donor graft from the lateral side of the talus after ligament release. This knowledge may allow better operative planning for use of these surfaces for osteochondral lesions within the foot and ankle, particularly in certain circumstances of a revision microfracture.

Anterior deltoid muscle tension quantified with shear wave ultrasound elastography correlates with pain level after reverse shoulder arthroplasty

Introduction Reverse shoulder arthroplasty (RSA) leads to medialization and distalization of the centre of rotation of the shoulder joint resulting in lengthening of the deltoid muscle. Shear wave ultrasound elastography (SWE) is a reliable method for quantifying tissue stiffness. The purpose of this study was to analyse if deltoid muscle tension after RSA correlates with the patients’ pain level. We hypothesized that higher deltoid muscle tension would be associated with increased pain. Material and methods Eighteen patients treated with RSA were included. Constant score (CS) and pain level on the visual analogue scale (VAS) were analysed and SWE was performed on both shoulders. All three regions of the deltoid muscle were examined in resting position and under standardized isometric loading. Results Average patient age was 76 (range 64–84) years and average follow-up was 15 months (range 4–48). The average CS was 66 points (range 35–89) and the average pain level on the VAS was 1.8 (range 0.5–4.7). SWE revealed statistically significant higher muscle tension in the anterior and middle deltoid muscle region in patients after RSA compared to the contralateral non-operated side. There was a statistically significant correlation between pain level and anterior deltoid muscle tension. Conclusion SWE revealed increased tension in the anterior and middle portion of the deltoid muscle after RSA in a clinical setting. Increased tension of the anterior deltoid muscle portion significantly correlated with an increased pain level. SWE is a powerful, cost-effective, quick, dynamic, non-invasive, and radiation-free imaging technique to evaluate tissue elasticity in the shoulder with a wide range of applications. Level of evidence Diagnostic study, Level III.

Upper Limb Muscles Activity during Punches in Virtual Reality Exergame on Standing and Sitting Position

Background: Physical activity (PA) provides various health benefits. Unfortunately, individuals with disabilities may experience health problems and greater obstacles to PA participation. Boxing exergame (EXG) based on virtual reality (VR) can be an alternative option to increase physical activity level because it is fun, relatively affordable and accessible. Punching in boxing requires complex movements, wherein the lower limbs are contributor for effective punches. An understanding of muscles activity is important to uncover the potential benefits of VR EXG.Aim: To evaluate the differences in upper limb muscles activity of the dominant side in standing compared to sitting position during punches.Material and methods: This was a cross-sectional study involving 15 healthy adult men. Surface electromyography examinations was performed on four upper limb muscles of the dominant side (upper trapezius, anterior deltoid, biceps, triceps) when delivering straight, hook and uppercut punches while playing VR EXG "Fitness Boxing" Nintendo Switch™ in standing and sitting position.Results: Fifteen healthy men (age 31.87±3.14 years old, BMI 23.77±2.47 kg.m-2) were participated in this study. No significant difference found in the percentage of maximum voluntary isometric contraction (%MVIC) values of the upper trapezius, anterior deltoid, biceps and triceps muscles of the dominant sides when the subjects delivered straight, hook and uppercut punches (p>0.05), except for upper trapezius muscle during uppercut punch in standing compared to sitting position (p=0.041).Conclusion: The VR EXG "Fitness Boxing" Nintendo Switch™ can be done in a standing or sitting position to get similar effect on the upper limb muscles.

Does exposure to startle impact voluntary reaching movements in individuals with severe-to-moderate stroke?

When movements of individuals with stroke (iwS) are elicited by startling acoustic stimulus (SAS), reaching movements are faster, further, and directed away from the body. However, these startle-evoked movements also elicit task-inappropriate flexor activity, raising concerns that chronic exposure to startle might also induce heightened flexor activity during voluntarily elicited movement. The objective of this study is to evaluate the impact of startle exposure on voluntary movements during point-to-point reaching in individuals with moderate and severe stroke. We hypothesize that startle exposure will increase task-inappropriate activity in flexor muscles, which will be associated with worse voluntarily initiated reaching performance (e.g. decreased distance, displacement, and final accuracy). Eleven individuals with moderate-to-severe stroke (UEFM = 8–41/66 and MAS = 0–4/4) performed voluntary point-to-point reaching with 1/3 of trials elicited by an SAS. We used electromyography to measure activity in brachioradialis (BR), biceps (BIC), triceps lateral head (TRI), pectoralis (PEC), anterior deltoid (AD), and posterior deltoid (PD). Conversely to our hypothesis, exposure to startle did not increase abnormal flexion but rather antagonist activity in the elbow flexors and shoulder horizontal adductors decreased, suggesting that abnormal flexor/extensor co-contraction was reduced. This reduction of flexion led to increased reaching distance (18.2% farther), movement onset (8.6% faster), and final accuracy (16.1% more accurate) by the end of the session. This study offers the first evidence that exposure to startle in iwS does not negatively impact voluntary movement; moreover, exposure may improve volitionally activated reaching movements by decreasing abnormal flexion activity.

The comparison of the shoulder muscle activation in patients with rotator cuff tear under an abduction brace among the three postures

Background: Immobilization using an abduction brace is essential for the relaxation of the rotator cuff and scapular muscles and the prevention of a retear in patients with rotator cuff tear after arthroscopic rotator cuff repair (ARCR). However, thus far, the comparison of the scapular muscle activities has not been compared among different postures under an abduction brace in patients after ARCR. Objectives: The purpose of our study was to compare the scapular muscle activities among the supine position, sitting position, and walking under an abduction brace before and after ARCR Study Design: Observational, repeated measures study. Methods: Twelve patients with full-thickness rotator cuff tears were studied. The mean patient age was 64.7 years. The scapular muscle activations of the ipsilateral limbs were measured using surface electromyography in three postures: supine position, sitting position, and walking. The integrated electromyography relative values of the upper trapezius, anterior deltoid, middle deltoid, and biceps brachii were compared preoperatively and at two weeks after ARCR. Results: The trapezius, biceps brachii, and middle deltoid in the walking showed significantly higher integrated electromyography relative values than those in the supine position, preoperatively and at two weeks after surgery. The anterior deltoid in the sitting position had significantly higher integrated electromyography relative values than those in the supine position. Conclusions: Postures affected the scapular muscle activities in ARCR patients under an abduction brace. Understanding the influence of posture on the scapular muscle activity after ARCR will help rehabilitation accurately and appropriately.