Differences In Muscle Activity Research Articles

Biomechanical risk factors for ACL injury differ between the sexes when performing a high-intensive exergame

Introduction
 Incidence rates in anterior cruciate ligament (ACL) injuries, which are linked to multiple factors, are higher in females than males (Sutton & Bullock, 2013). However, the main contributors to the difference in risk are biomechanical factors such as increased knee valgus (KV), knee internal rotation (KIR), or decreased hip flexion (HF; Seyedahmadi et al., 2022). Returning back to sports after an injury requires extensive rehabilitation as well as training of dual-task situations in order to be physically and cognitively prepared. Exergaming represents a dual task including a cognitive and a motor component and may be used as training modality during rehabilitation. It is known that performing a dual-task leads to altered landing movement patterns in healthy athletes (Dai et al., 2018). Before an exergame for rehabilitation after ACL injury can be implemented and tailored to the specific needs of female and male athletes, the movement patterns of males and females need to be understood. Therefore, the aim of this study was to identify biomechanical differences between males and females when performing a high-intensive exergame.
 Methods
 Using 3D-motion capture (Vicon) kinematics were measured in 18 healthy athletes (9 male, 9 female) during a 25-min exergame (Sphery Racer, ExerCube). The exergame included nine different exercises of which 8 were used for analysis. The exercises were separated into neutral (squat, jump, burpee) and side-specific exercises (low-touch, mid-touch, high-touch, punch, lunge). For analysis, the maximal KV, maximal KIR, and the minimal HF were extracted during 10-30° knee flexion. These maximal values were then compared between the sexes, the exercises, and both legs with a linear mixed model, for each the neutral and the side-specific exercises.
 Results
 A main effect of sex was only found for side-specific exercises in KIR (F(1, 16) = 6.1, p = .02) with females exhibiting higher values. For KV and HF in side-specific exercises as well as all variables in neutral exercises, no significant main effect for sex was found. However, there was a main effect of exercise in KV; KIR, and HF in neutral (p < .001) as well as in side-specific exercises (p < .001).
 Discussion/Conclusion
 Differences in KIR between males and females primarily exist during touches and punches. Therefore, exergames should incorporate this fact to counteract increased risk for knee injuries in females.
 References
 Dai, B., Cook, R. F., Meyer, E. A., Sciascia, Y., Hinshaw, T. J., Wang, C., & Zhu, Q. (2018). The effect of a secondary cognitive task on landing mechanics and jump performance. Sports Biomechanics, 17(2), 192–205. https://doi.org/10.1080/14763141.2016.1265579
 Seyedahmadi, M., Minoonejad, H., Karimizadeh Ardakani, M., Heidari, Z., Bayattork, M., & Akbari, H. (2022). What are gender differences in lower limb muscle activity during jump-landing tasks? A systematic review and meta-analysis. BMC Sports Science, Medicine & Rehabilitation, 14(1), Article 77. https://doi.org/10.1186/s13102-022-00469-3
 Sutton, K. M., & Bullock, J. M. (2013). Anterior cruciate ligament rupture: Differences between males and females. The Journal of the American Academy of Orthopaedic Surgeons, 21(1), 41–50. https://doi.org/10.5435/jaaos-21-01-41

Predicting Dysphonia by Measuring Surface Electromyographic Activity of the Supralaryngeal Muscles.

This study set out to investigate whether individuals with dysphonia, as determined by either self-assessment or clinician-based auditory-perceptual judgment, exhibited differences in perilaryngeal muscle activities using surface electromyography (sEMG) during various phonatory tasks. Additionally, the study aimed to assess the effectiveness of sEMG in identifying dysphonic cases. A total of 77 adults (44 women, 33 men, Mage = 30.4 years) participated in this study, with dysphonic cases identified separately using either a 10-item Voice Handicap Index (VHI-10) or clinician-based auditory-perceptual voice quality (APVQ) evaluation. sEMG activities were measured from the areas of suprahyoid and sternocleidomastoid muscles during prolonged vowel /i/ phonations at different pitch and loudness levels. Normalized root-mean-square value against the maximal voluntary contraction (RMS %MVC) of the sEMG signals was obtained for each phonation and compared between subject groups and across phonatory tasks. Additionally, binary logistic regression analysis was performed to determine how the sEMG measures could predict the VHI-10-based or APVQ-based dysphonic cases. Participants who scored above the criteria on either the VHI-10 (n = 29) or APVQ judgment (n = 17) exhibited significantly higher RMS %MVC in the right suprahyoid muscles compared to the corresponding control groups. Although the RMS %MVC value from the right suprahyoid muscles alone was not a significant predictor of self-evaluated dysphonic cases, a combination of the RMS %MVC values from both the right and left suprahyoid muscles significantly predicted APVQ-based dysphonic cases with a 69.66% fair level. This study found that individuals with dysphonia, as determined by either self-assessment or APVQ judgment, displayed more imbalanced suprahyoid muscle activities in voice production compared to nondysphonic groups. The combination of the sEMG measures from both left and right suprahyoid muscles showed potential as a predictor of dysphonia with a fair level of confidence. https://doi.org/10.23641/asha.25112804.

People With Low Back Pain Exhibit Higher Trunk Muscle Activity and Impaired Postural Control During Static and Dynamic Functional Tasks: A Cross-Sectional Study.

The study compared superficial trunk muscle activity and postural control among an active extension subgroup of people with nonspecific chronic low back pain (AE-NSCLBP) with painfree controls during functional tasks. Thirty-two people (17 people with low back pain [LBP] and 15 painfree controls) participated in this study. Muscle activity of 5 trunk muscles and postural control were investigated during both standing tasks (eyes open/closed; single/double-leg balance) and dynamic functional tasks (spinal forward flexion and return, and a sit to stand transfer). Results showed that during single-leg standing, people with AE-NSCLBP exhibit higher muscle activity than painfree controls for 3 trunk muscles, especially with their eyes closed. There were no significant differences in muscle activity between eye conditions during double-leg standing and sit to stand transfer, forward flexion, and return from flexion. The AE-NSCLBP subgroup also demonstrated significantly impaired postural control (lower time to boundary) in 4 of 8 conditions, especially during single-leg standing and with their eyes closed. These findings show people with LBP typically demonstrated greater trunk muscle activity and poorer postural control while maintaining standing posture. This pattern was most evident when the postural challenge was higher, such as single-leg standing or with eyes closed. While this study design cannot infer causality, these findings have implications for LBP rehabilitation, particularly regarding approaches which seek to alter muscle activation among people with LBP.

Analyzing muscle thickness changes in lateral abdominal muscles while exercising using virtual reality.

[Purpose] Virtual reality (VR) rehabilitation has become popular in the medical field. VR-guided exercises (VR-ge) have demonstrated positive effects on gait and trunk control. Trunk muscle activation, particularly that of the transversus abdominis (TrA), is responsible for these improvements. However, the difference in muscle activation between VR and real space remains unclear. Therefore, this study aimed to clarify the differences in trunk muscle activation during exercise therapy performed in VR and real space. [Participants and Methods] A total of 22 healthy male volunteers were divided into two equal groups: VR-ge and Control exercise (C-e) groups. Both groups performed reaching exercises in a seated position. Ultrasound imaging was used to measure the thicknesses of the right external oblique, internal oblique, and TrA muscles, both at rest and during the reaching exercises performed in six different directions. [Results] No significant differences were observed in TrA muscle thickness changes between the groups before the intervention. However, after the intervention, the VR-ge group showed significantly greater TrA muscle thickness changes during reaching compared to that of the C-e group. [Conclusion] VR-ge increased TrA activation during reaching compared to exercising in real space.

Surface electromyography of the vastus lateralis and gluteus medius muscles in post-operative T3-L3 hemilaminectomy dogs: a prospective controlled observational study.

The objective of this study was to determine if surface electromyography (sEMG) demonstrates differences in muscle activation between normal and dogs recovering from spinal cord injury due to intervertebral disk extrusion. Two groups of client-owned small-breed chondrodysplastic-type dogs were tested. Group 1 consisted of seven ambulatory paraparetic dogs that had undergone a hemilaminectomy procedure in the T3-L3 region for intervertebral disk extrusion 1 month prior. Group 2 was made up of seven normal dogs that had no history of intervertebral disk disease or spinal surgery. Each subject walked 10 feet on a nonslip surface for at least five gait cycles for the sEMG to capture muscle activation of the vastus lateralis and gluteus medius, bilaterally. Muscle activation was quantified as the total myoelectric output area under the curve, averaged across all gait cycles. Muscle activation was significantly greater in the post-operative hemilaminectomy group (p = 0.012). There was a significant difference in muscle activation between each hindlimb in the post-operative hemilaminectomy group, but not in the normal group. The muscle activation was significantly lower on the side that underwent surgery compared to the opposite limb (p = 0.0034). Post-operative hemilaminectomy dogs have greater hindlimb muscle activation compared to normal dogs, which likely represents a lack of descending inhibition secondary to upper motor neuron syndrome. The side of surgery is correlated with decreased muscle activation. Surface EMG can be used to evaluate muscle activity in dogs recovering from spinal decompression surgery.

Characteristics of walking techniques with different pelvic height and pelvic rotation: effect on muscle activation and energy consumption.

Purpose: Previous studies have proven that modifications in the natural walking technique alter muscle activation and energy consumption. This research aimed to determine the differences in muscle activation, energy consumption, kinematic characteristics, perceived muscular exertion and perceived cardio-respiratory fatigue between natural and modified walking techniques with altered pelvic height and rotation. Methods: Nine physically active, non-injured males walked on a treadmill. Modified walking techniques assumed maintenance of constant pelvic height and application of maximal pelvic rotation. Walking speed was subtransit - 0.4 km/h less than the transit. Sampled variables were: average normalized maximal activation during contact and swing phase relativized to maximal voluntary activation, average submaximal oxygen consumption relativized to body mass and subtransit speed, average step length and frequency, rating of perceived muscular exertion and perceived cardio-respiratory fatigue. Muscle activation, energy consumption and kinematic characteristics were assessed throughout each walking session. Perceived muscular exertion and perceived cardio-respiratory fatigue were evaluated post-session. Electromyographic activity was assessed for rectus femoris, gluteus maximus, vastus medialis, biceps femoris, tibialis anterior and gastrocnemius lateralis. Results: The most significant changes in muscle activation were observed during the contact phase. A decrease in pelvic height increased muscle activation of rectus femoris, vastus medialis and gastrocnemius lateralis. An increase in pelvic rotation increased muscle activation of all monitored muscles except for gluteus maximus. Both modifications increased energy consumption, perceived muscular exertion and perceived cardio-respiratory fatigue, and altered kinematic characteristics. Conclusions: Modifications in pelvic height and rotation at the same walking speed alter muscle activation, energy consumption, kinematic characteristics, perceived exertion and fatigue.

Lower-Limb Myoelectric Calibration Postures for Transtibial Prostheses.

The use of an agonist-antagonist muscle pair for myoelectric control of a transtibial prosthesis requires normalizing the myoelectric signals and identifying their co-contraction signature. Extensive literature has explored the relationship between body posture and lower-limb muscle activation level using surface electromyography (EMG), but it is unknown how these relationships hold after amputation. Using a virtual tracking task, this study compares the effect of three different calibration postures (seated, standing, dynamic) on user tracking ability while in two tracking postures (seated, standing) for 18 able-bodied (AB) subjects and 9 subjects with transtibial (TT) amputation. As expected, AB subjects produced statistically significant differences in muscle activation for gastrocnemius (GAS) when seated vs. standing during calibration (p = 8.8e-4), but not for tibialis anterior (TA) (p = 0.76). TT subjects, however, showed no significant differences in GAS or TA between seated and standing (p = 0.90, 0.60 respectively). It was also determined that normalizing EMG by the global maximum signal observed (standard in biomechanic analysis) is undesirable for myoelectric control. For best general results with this framework, calibration in both seated and dynamic postures is recommended, taking the normalization information from the seated posture and the narrowest co-contraction slopes from the two.

Kinematic changes of the trunk and lower limbs during voluntary lateral sway postural control in adults with low back pain.

Introduction: Voluntary lateral weight shifting is essential for gait initiation. However, kinematic changes during voluntary lateral weight shifting remain unknown in people with low back pain (LBP). This study aims to explore the differences in kinematics and muscle activation when performing a voluntary lateral weight shifting task between patients with LBP and asymptomatic controls without pain. Methods: Twenty-eight participants volunteered in this study (14 in both the LBP group and the control group). The Sway Discrimination Apparatus (SwayDA) was used to generate a postural sway control task, mimicking lateral weight shifting movements when initiating gait. Kinematic parameters, including range of motion (ROM) and standard deviation of ROM (Std-ROM) of the lumbar spine, pelvis, and lower limb joints, were recorded using a motion capture system during lateral weight shifting. The electroactivity of the trunk and lower limb muscles was measured through surface electromyography using root mean square (RMS). The significant level was 0.05. An independent t-test was employed to compare kinematic parameters, and muscle activation between the LBP group and the control group. A paired-sample t-test, adjusted with Bonferroni correction (significant level of 0.025), was utilized to examine differences between the ipsilateral weight shifting towards side (dominant side) and the contralateral side. Results: The results of kinematic parameters showed significantly decreased ROM and std-ROM of the ipsilateral hip in the transverse plane (tROM = -2.059, p = 0.050; tstd-ROM = -2.670, p = 0.013), as well as decreased ROM of the ipsilateral knee in the coronal plane (t = -2.148, p = 0.042), in the LBP group compared to the control group. For the asymptomatic controls, significantly larger ROM and ROM-std were observed in the hip and knee joints on the ipsilateral side in contrast to the contralateral side (3.287 ≤ t ≤ 4.500, 0.001 ≤ p≤ 0.006), but no significant differences were found between the two sides in the LBP group. In addition, the LBP group showed significantly lower RMS of the biceps femoris than the control group (tRMS = -2.186, p = 0.044). Discussion: Patients with LBP showed a conservative postural control pattern, characterized by reduced ROM of ipsilateral joints and diminished activation of the biceps femoris. These findings suggested the importance of voluntary postural control assessment and intervention to maximize recovery.

Upright versus Horizontal Squat Jumps: A comparison of peak force, peak velocity, peak power and muscle activity in male athletes

Sports performance coaches and rehabilitation specialists commonly prescribe explosive squat jumps (SJ) in the upright position to improve lower body power using loads based upon an individual’s one-repetition maximum (1RM) back squat. Recently, using a horizontal leg press to perform SJ has become popular purportedly due to its less technical nature. To date, little research exists comparing upright and horizontal SJ. Therefore, this investigation examined peak force, peak velocity, peak power and muscle activity of upright versus horizontal SJ using loads based upon each condition’s respective 1RM. Twelve males completed two sets of three repetitions of SJ at 20%, 30%, 40%, 50% and 60%1RM. Statistical significance was set to P ≤ 0.05. No significant differences existed between trial 1 and 2 for any measures. Two-way analysis of variance revealed a) no significant difference in peak force between the SJ conditions at any intensity; b) significantly greater peak velocity during upright SJ at all intensities; c); significantly greater peak power during upright SJ at all intensities; and d) no difference in muscle activity between SJ conditions. In conclusion, in a key measure of performance, power output during upright SJ was significantly greater than during horizontal SJ.

Event structure reflected in muscle activation differences in Austrian Sign Language (ÖGS) verbs

This paper aims to introduce kinematic motion capture analysis and electromyography(EMG) methodology in the context of experimental investigations involving signlanguages. While motion capture has been employed in previous sign language research,the application of EMG is relatively novel. We utilized both motion capture andEMG techniques to examine the disparities in muscle activation associated with theproduction of telic verb signs (with boundary marking, e.g. the verb arrive) andatelic verb signs (lacking boundary marking, e.g. the verb run) in Austrian SignLanguage (ÖGS). The data analysis revealed that the visual boundary marking inherentin the production of telic signs, which is kinematically characterized by heightenedacceleration, jerk, and deceleration at the conclusion of a sign, is generated by increased activation in upper arm muscles during the sign and hold interval for telics comparedto atelics. In contrast, the majority of atelics exhibited a repeated movement, whichcontributed to more pronounced muscle activation in the forearm compared to telics.The EMG/motion capture combined method applied to sign language production offersnovel insights into linguistics of sign language that were previously inaccessible.

Children with developmental coordination disorder have less variable motor unit firing rate characteristics across contractions compared to typically developing children.

Understanding the nuances of neuromuscular control is crucial in unravelling the complexities of developmental coordination disorder (DCD), which has been associated with differences in skeletal muscle activity, implying that children with DCD employ distinct strategies for muscle control. However, force generation and control are dependent on both recruitment of motor units and their firing rates and these fine details of motor function have yet to be studied in DCD. The purpose of this study was therefore to compare motor unit characteristics in a small muscle of the hand during low level, handgrip contractions in typically developing (TD) children and children with DCD. Eighteen children (9 TD vs. 9 DCD) completed a series of manual handgrip contractions at 10 ± 5% of their maximum voluntary contraction. High density surface electromyography was used to record excitation of the first dorsal interosseus muscle. Recorded signals were subsequently decomposed into individual motor unit action potential trains. Motor unit characteristics (firing rate, inter-pulse interval, and action potential amplitude) were analysed for contractions that had a coefficient variation of <10%. This study found few differences in average motor unit characteristics (number of motor units: TD 20.24 ± 9.73, DCD 27.32 ± 14.00; firing rate: TD 7.74 ± 2.16 p.p.s., DCD 7.86 ± 2.39 p.p.s.; inter-pulse interval: TD 199.72 ± 84.24 ms, DCD 207.12 ± 103 ms) when force steadiness was controlled for, despite the DCD group being significantly older (10.89 ± 0.78 years) than the TD group (9.44 ± 1.67 years). However, differences were found in the variability of motor unit firing statistics, with the children with DCD surprisingly showing less variability across contractions (standard deviation of coefficient of variation of inter-pulse interval: TD 0.38 ± 0.12, DCD 0.28 ± 0.11). This may suggest a more fixed strategy to stabilise force between contractions used by children with DCD. However, as variability of motor unit firing has not been considered in previous studies of children further work is required to better understand the role of variability in motor unit firing during manual grasping tasks, in all children.

Walking Kinematic Coordination Becomes More In-Phase at Extreme Inclines.

Previous research has shown that there are differences in mechanical energy, kinematics, and muscle activation when comparing walking on level and incline surfaces, especially on inclines above 15%. Muscle activations are significantly different while walking on extreme inclines, suggesting a different coordination pattern. We utilized continuous relative phase to assess walking kinematic coordination with respect to increased incline angles. Twelve healthy, college-aged individuals walked for 7 inclines of 1minute each on a motorized treadmill at 3mph at 0%, 5%, 10%, 15%, 20%, 25%, and 30% inclines. Kinematic data were collected during the last 20seconds of each stage (120Hz). Segmental and joint angles and angular velocities in the sagittal plane were calculated, from which continuous relative phase was determined for 3 joint couples: hip-knee, hip-ankle, and knee-ankle. There were significant differences in the coordination patterns during the first part of the contact phase in the hip-knee and hip-ankle couplings between the 0% and 30% inclines, with all 3 joint couplings becoming more in-phase at inclines above 15%. Importantly, the hip-kneecoupling changed significantly from more out-of-phase to more in-phase between 10% and 15% incline. Shifting lower-extremity joint coordination in response to extreme inclines identifies potential coordinative strategies to achieve steep walking.

Sex-Based Differences in Lower Extremity Kinematics During Dynamic Jump Landing Tasks After Neuromuscular Fatigue of the Hip Extensors and Knee Flexors.

Neuromuscular fatigue can increase the activation of antagonist muscles, thereby reducing the moment produced by the agonist. During the deceleration phase of landing, hip extensor and knee flexor muscles contract eccentrically to counteract the external hip flexion moment. Decreased hip flexion is associated with greater knee extensor moments and risk of injury. To investigate sex-based differences in kinematics and muscle activity after neuromuscular fatigue of the hip extensors and knee flexors during dynamic single-leg tasks. Controlled laboratory study. In this study, 9 female (age, 22.3 ± 3.4 years) and 7 male participants (age, 21.3 ± 2.6 years) completed the triple hop (THop) for distance and single-leg drop-jump (SJump) tasks before and after a fatigue protocol consisting of eccentric hip extension and knee flexion. Motion capture and electromyography were used to compare lower extremity kinematics and muscular activation between the sexes. During the THop, neuromuscular fatigue resulted in significantly decreased maximum hip flexion angles (P = .01), maximum knee flexion angles (P = .039), and an effect of sex on all hip flexion angles, where both sexes saw decreased hip flexion postfatigue (P = .033). A significant interaction of fatigue and sex on hip flexion angular velocity was observed during the SJump, indicating that men experienced an increase while women experienced a decrease in hip flexion angular velocities due to fatigue (P = .03). Gluteus maximus activation was increased, and erector spinae activation was decreased postfatigue in women during the THop (P = .053 and P = .023, respectively). Results indicate that men and women compensated differently after fatigue of the hip extensors and knee flexors. Women more commonly assumed an erect landing posture associated with increased injury risk after fatigue of the hip extensors and knee flexors.

Does enforcing glenohumeral joint stability matter? A new rapid muscle redundancy solver highlights the importance of non-superficial shoulder muscles.

The complexity of the human shoulder girdle enables the large mobility of the upper extremity, but also introduces instability of the glenohumeral (GH) joint. Shoulder movements are generated by coordinating large superficial and deeper stabilizing muscles spanning numerous degrees-of-freedom. How shoulder muscles are coordinated to stabilize the movement of the GH joint remains widely unknown. Musculoskeletal simulations are powerful tools to gain insights into the actions of individual muscles and particularly of those that are difficult to measure. In this study, we analyze how enforcement of GH joint stability in a musculoskeletal model affects the estimates of individual muscle activity during shoulder movements. To estimate both muscle activity and GH stability from recorded shoulder movements, we developed a Rapid Muscle Redundancy (RMR) solver to include constraints on joint reaction forces (JRFs) from a musculoskeletal model. The RMR solver yields muscle activations and joint forces by minimizing the weighted sum of squared-activations, while matching experimental motion. We implemented three new features: first, computed muscle forces include active and passive fiber contributions; second, muscle activation rates are enforced to be physiological, and third, JRFs are efficiently formulated as linear functions of activations. Muscle activity from the RMR solver without GH stability was not different from the computed muscle control (CMC) algorithm and electromyography of superficial muscles. The efficiency of the solver enabled us to test over 3600 trials sampled within the uncertainty of the experimental movements to test the differences in muscle activity with and without GH joint stability enforced. We found that enforcing GH stability significantly increases the estimated activity of the rotator cuff muscles but not of most superficial muscles. Therefore, a comparison of shoulder model muscle activity to EMG measurements of superficial muscles alone is insufficient to validate the activity of rotator cuff muscles estimated from musculoskeletal models.

Ankle Biomechanics During Multidirectional Landings in Athletes With Chronic Ankle Instability.

Assessing and understanding the control of the ankle during multidirectional jump landings in athletes with chronic ankle instability (CAI) would help health professionals develop interventions to reduce the risk of recurrent injuries. The aim of this study was to investigate the angle, angular velocity, and movements of the ankle joint, and the muscle activity of peroneus longus (PL), tibialis anterior (TA), and gastrocnemius (GAS) muscles during multidirectional landings in athletes with CAI. Nineteen athletes with CAI (≤25 Cumberland Ankle Instability Tool-Thai Score) participated. A Vicon Nexus motion analysis system synchronously collected data with an AMTI force plate and surface electromyography (EMG) to capture kinematics, kinetics, and muscle activity, respectively. Participants were asked to perform single-leg jump-landing tests in forward (0°), 30° diagonal, 60° diagonal, and lateral (90°) directions. Ankle joint kinematics, kinetics, and muscle activity of PL, TA, and GAS were analyzed. Repeated measure ANOVA (analysis of variance) and Friedman tests were used to analyze the main effects of the jump-landing direction. Athletes with CAI exhibited significant differences in ankle angles, angular velocities, ankle movements, and average muscle activity of GAS between directions. Greatest average EMG of GAS muscle was observed during landing in the lateral direction compared with the forward and 30° diagonal directions. Lateral and diagonal direction movements showed the greatest risks associated with recurrent ankle sprains. Impairments of neuromuscular control in both pre-landing and landing phases were observed in athletes with CAI when considered alongside previously published data. Laboratory-based observational study.

No Evidence of Short-Term Changes in Muscle Activity Elicited by Dry Needling in Chronic Unilateral Shoulder Pain Patients.

The aim of the study was to assess short-term changes in shoulder muscle activity elicited by dry needling in chronic unilateral shoulder pain patients. A double-blind, placebo-controlled clinical trial was conducted, in which 30 volunteers with unilateral shoulder pain (USP) were recruited and randomly assigned to either real or sham dry needling conditions. Pain intensity scores, pressure pain threshold (PPT), glenohumeral internal rotation angles, and electromyographic activity during isotonic shoulder tasks (shoulder flexion and extension) were assessed before, immediately and 72 h after the intervention in the infraspinatus and deltoid muscles. A single application of real dry needling resulted in lower pain intensity scores and a larger range in glenohumeral internal rotation 72 h after the intervention in comparison with sham dry needling. No differences in PPT or muscle activity were observed due to the intervention. A single application of real dry needling resulted in clinically significant changes in the short-term. No differences were detected in muscle activation in the infraspinatus or deltoid muscles. Complementary interventions and longer follow-up times may be required to observe changes in muscle activity.

In Vivo Kinematic Analysis of the Axial Shoulder Rotation in the Standing and Supine Positions Using 3D/2D Registration and Electromyography.

Background There has been no report comparing shoulder kinematics and muscle activities during axial shoulder rotation in different positions. The purpose of this study was to investigate differences in shoulder kinematics and muscle activities during axial shoulder rotation in healthy subjects between standing and supine positions using three-dimensional/two-dimensional (3D/2D) registration techniques and electromyography (EMG). Methods Eleven healthy males agreed to participate in this study. We recorded the fluoroscopy time during active shoulder axial rotation with a 90° elbow flexion in both standing and supine positions, simultaneously recording surface EMG of the infraspinatus, anterior deltoid, posterior deltoid, and biceps brachii. Three-dimensional bone models were created from CT images, and shoulder kinematics were analyzed using 3D/2D registration techniques. Muscle activities were evaluated as a ratio of mean electromyographic values to 5-sec maximum voluntary isometric contractions. Results Scapular kinematics during axial shoulder rotation in the supine position showed similar patterns with those in the standing position. The scapula was more posteriorly tilted and more downwardly rotated in the supine posture than in standing (P < 0.001 for both). Acromiohumeral distance (AHD) in the supine posture was significantly larger than in standing. Muscle activities showed no significant differences between postures except for biceps (P < 0.001). Discussion Shoulder kinematics and muscle activities during axial rotation were similar in pattern between standing and supine postures, but there were shifts in scapular pose and AHD. The findings of this study suggest that posture may be an important consideration for the prescription of optimal shoulder therapy following surgery or for the treatment of shoulder disorders.

Can different variations of suspension exercises provide adequate loads and muscle activations for upper body training?

The purpose of this study was to assess the differences in muscle activation (EMG) and body weight distribution (%BW) between suspension (TRX™ push-up and TRX™ inverted row) and conventional exercises (bench press and lying barbell row) using different contraction types (isometric and isotonic) and position variations (feet on the ground [FG] and feet on suspension device [FD]). It was also used to determine the intensity of the force applied to the straps of the suspension device corresponding to one repetition maximum (1-RM). Twelve male athletes (ages-24.5±4.2 years (mean±standard deviation [SD]); Height-181.0±6.8 cm; body mass-83.08±6.81 kg) participated in this study. Two suspension devices were used, one for the FD variation and one for the FG variation pectoralis major (PM) and triceps brachii (TRI) activations were assessed during the TRX™ push-up and bench press exercises. Transversus trapezius (TRA) and biceps brachii (BB) activations were assessed during the TRX™ inverted row and lying barbell row exercises. The results showed significant differences between exercises (FG and FD variations of TRX™ push-up and bench press) in PM activities (isometric and isotonic) (p≤0.05). However, these differences were only observed during isometric TRI activation (p≤0.05). In the FG and FD variations of the TRX™ inverted row and lying barbell row exercises, there were only differences in the isometric contractions of the TRA and BB (p≤0.05). In the suspension device of push-ups and inverted row for the FD variations, 70.5% and 72.64% of 1-RM intensity were obtained, respectively. Similar responses to training intensities and muscle activations can be obtained in suspension exercises and conventional exercises. FD variations of suspension exercises can be more effective in terms of muscle activations than FG variations, and isotonic suspension exercises increase exercise intensity more than isometric suspension exercises.

The effects of hand dominance, fatigue, and sex on muscle activation during a repetitive overhead fatiguing task

Previous studies have shown that the dominant arm is generally stronger and more resistant to fatigue. However, whether there are side differences in shoulder muscle activation during a fatiguing upper limb task, and whether this varies according to sex, is unknown. Thirty right-handed adults (15 females) were recruited to complete two sessions of an overhead repetitive fatiguing task (shoulder flexion between 90 and 135° at 1 Hz), performed in two separate sessions with their dominant arm (DA) and non-dominant arm (NDA) until exhaustion. Electromyographic (EMG) data was collected from 11 shoulder muscles of the moving arm, and their activation amplitude (RMS) and activation variability (SD) were assessed. Results show that time to exhaustion was not affected by arm or by sex. There were some main arm effects on EMG activity amplitude, with higher activity on the DA's pectoralis major (p < 0.001), and on the NDA's middle (p = 0.009) and posterior deltoid (p = 0.001) and infraspinatus (p < 0.001). The pectoralis major was affected by arm and fatigue mostly in males. Their DA's pectoralis major activity amplitude was higher, and the amplitude variability was lower, compared to the NDA, with both parameters showing fatigue-dependent decreases at the NDA only (arm x sex x fatigue: RMS: p = 0.007; SD: p = 0.001). As for females, the DA variability of their lower trapezius was smaller, and that of their subscapularis was higher, compared to the NDA (sex x arm, p = 0.028, p = 0.05). There was also more EMG variability on the supraspinatus' dominant side, and on the posterior deltoid and infraspinatus ND side. Results show an overhead shoulder flexion task dependency on pectoralis major control in males, and on lower trapezius and shoulder girdle stabilizers in females, which could be related to both sex- and gender-based factors. This knowledge can help identify side-specific injury risk factors due to overhead work in males and females, and help determine the appropriateness of implementing sex-specific workplace protocols, including alternating arms as fatigue compensatory and recovery strategies.

Effects of Band-Resisted Abduction on Muscle Activity between the Barbell Hip Thrust and Barbell Glute Bridge

The importance of hip extensor and abductor muscles for sport performance and injury reduction is well-documented. To target these muscle groups, the barbell hip thrust and barbell glute bridge are used to load the posterior kinetic chain while band-resisted abduction exercises, like band-resisted side stepping, target the lateral kinetic chain. However, combining band-resisted hip abduction with barbell hip-extension dominant exercises has not yet been investigated. In this study, ten male subjects underwent a two-part research protocol with surface electromyography (sEMG) measured during a 5-repetition maximum (5-RM) load performance to determine differences in peak and mean muscular activity between band-resisted barbell hip thrust (BBHT) and barbell hip thrust (BHT), and between band-resisted barbell glute bridge (BBGB) and barbell glute bridge (BGB). The results indicated three significant differences between the pairs, with both banded conditions eliciting greater sEMG activity in the Upper Gluteus Maximus compared to non-banded conditions. However, BGB unexpectedly elicited greater sEMG activity in the Gluteus Medius compared to BBGB. The differences in muscle activity could potentially be explained by reciprocal inhibition and synergistic dominance. Further research is needed to make definitive statements on the superiority of band-resisted barbell exercises over non-banded barbell exercises and transferability to sport performance.