Differences In Muscle Activity Research Articles

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.

Effects of Pseudo-Weight Resistance Training Using Mixed-Reality Technology on Muscle Activation in Healthy Adults: A Preliminary Study

The present study investigated the feasibility and effectiveness of pseudo-weight resistance training using mixed-reality (MR) technology for shoulder muscle activation in healthy individuals. Thirty-two healthy students aged 20~35 years participated in this preliminary study and were divided into two groups. Participants in the MR group received 30 min of training three times a week for 4 weeks using a customized MR-based pseudo-weight resistance training system. Those in the control group performed the same exercises using a conventional training program. Muscle activation of the deltoids, upper trapezius, infraspinatus, and supraspinatus were measured before and after the intervention. There was a statistically significant difference in middle deltoid, upper trapezius, and supraspinatus muscle activation in the MR group (p &lt; 0.05), while the control group showed a significant difference in the anterior and middle deltoid, upper trapezius, and supraspinatus (p &lt; 0.05). Regarding the between-group comparison, no statistically significant difference was observed for all six muscles (p &gt; 0.05). Without any superiority of physical weight resistance training in the pseudo-weight training program, an MR-based pseudo-weight resistance training system can potentially be used for muscle-strengthening training, especially for early rehabilitation programs. However, further study using a large sample size with a long experimental duration is needed for more evidence of the presented technology and its use in home training.

Comparison of EMG activity in the adductors during Copenhagen adductor exercise and Adductor slide in male ice hockey players

Objectives: The aim of this study is to estimate differences in muscle activity of the adductor longus- and adductor magnus muscle during the AS with different amounts of external resistance compared to CAE in male, adult, ice hockey players. Methods: This cross-sectional study compared muscular activity (EMG) during CAE and AS in a convenience sample of male ice hockey players. The players performed AS with different external loads and EMG readings was compared to the CAE. The main outcome was differences in mean %MVIC with CAE as a reference. Differences were compared using paired t-tests and standardized effect sizes (Cohen’s d) were calculated. Results: 21 injury free male ice hockey players participated in the study. We found a statistically significant lesser muscle activation during AS compared to CAE (p&lt;0.05), Differences in mean %MVC during concentric contractions had a range between -60% (95% CI:-82%; -37%) and -28% (-51%; -6%) for the adductor longus, and between -67% (-93%; -41%) and -36% (-53%; -19%) for the adductor magnus. Differences in mean %MVC during eccentric contractions had a range between -70% (-88%; -53%) ad -62% (-78%; -46%) for the adductor longus and between -78% (-101%; -55%) and -68% (-88%; -48%) for the adductor magnus. The effect size was moderate to high (0.45-1-85) for all differences in mean. Conclusion: The AS produces significantly less muscle activation than the CAE, concentrically and eccentrically as well as with and without external loads.

Exploring the differences in muscle activation of unilateral transtibial amputees during rehabilitation exercises and walking

Exploring the differences in muscle activation of unilateral transtibial amputees during rehabilitation exercises and walking

Biomechanical comparison of human trunk and thigh muscle activity during walking and horseback riding activity

IntroductionHippotherapy is a physical therapy tool that utilizes horseback riding to improve strength, coordination, gait, and balance. These benefits may be linked to similarities in kinematics and muscle activation between horseback riding and normal human gait, but this is not well represented in the literature, especially for muscle activation. The purpose of this study was to investigate the relationships between muscle activation of horseback riding and healthy human gait. MethodsThe muscle activation of nine healthy female participants (age 18–22) were recorded during walking and horseback riding trials using surface electromyography (EMG). Muscles analyzed include rectus abdominis, lumbar erector spinae, rectus femoris and biceps femoris. Activation waveforms during walking and riding were generated, and from this average and maximum contraction magnitudes were recorded. ResultsAverage muscle activation was significantly greater in riding for the left (p = 0.008) and right (p = 0.04) biceps femoris. Additionally, average and maximal activation of the left erector spinae were significantly greater in riding (W = 4; critical value for W at n = 9 is 5). Remaining differences in muscle activation between walking and riding were non-significant. DiscussionPeak and average muscle activation magnitude across the gait cycle were similar for most muscle groups. When present, differences were greater in riding. Despite these similarities, EMG waveforms displayed more predictable temporal patterns in walking. ConclusionThese findings suggest that hippotherapy could be used to elicit muscle excitation similar to that of normal gait, which may have promising implications for rehabilitation targeting gait correction.

Exploring the Design of Upper Limb Strength Training Through High-Intensity Interval Training Combined With Exergaming: Usability Study.

High-intensity interval training (HIIT) has become a popular exercise strategy in modern society, with the Tabata training method being the most popular. In the past, these training methods were mostly done without equipment, but incorporating exergaming into the training may provide a new option for muscle training. The aim of this study was to explore the differences in upper limb muscle activation using an HIIT program combined with exergaming. A total of 15 healthy male participants were recruited for the study, and the differences in muscle activation were compared between push-ups and exergaming (Nintendo Switch Ring Fit Adventure with the Ring-Con accessory) during HIIT. Prior to the tests, participants underwent pretests, including maximal voluntary contractions of various muscle groups, maximal push-up tests, and maximal movement tests using the exergaming device. The push-up and exergaming tests were conducted on separate days to avoid interference, with a warm-up period of 5 minutes on a treadmill before testing. Muscle activation in the lateral and anterior portions of the deltoid muscle, the sternal and clavicular heads of the pectoralis major muscle, and the latissimus dorsi muscle were measured during the maximal voluntary contractions and single-round tests for each exercise mode. A repeated measures ANOVA was used to assess the variations in muscle activation observed across the 2 distinct modes of exercise, specifically push-ups and exergaming. In exergaming, the number of repetitions for push-ups was significantly fewer than for single-site exercises across both exhaustive (mean 23.13, SD 6.36 vs mean 55.67, SD 17.83; P=.001; effect size [ES]: 2.43) and single-round (mean 21.93, SD 7.67 vs mean 92.40, SD 20.47; P=.001; ES: 4.56) training. Heart rate differences were not significant (all P>.05), yet exergaming led to better muscle activation in specific muscle groups, particularly the right anterior deltoid (mean 48.00%, SD 7.66% vs mean 32.84%, SD 10.27%; P=.001; ES: 1.67) and right pectoralis major (sternal head: mean 38.99%, SD 9.98% vs mean 26.90%, SD 12.97%; P=.001; ES: 1.04; clavicular head: mean 43.54%, SD 9.59% vs mean 30.09%, SD 11.59%; P=.002; ES: 1.26) during exhaustive training. In single-round training, similar patterns were observed with the anterior deltoid (mean 51.37%, SD 11.76% vs mean 35.47%, SD 12.72%; P=.002; ES: 1.30) and pectoralis major (sternal head: mean 53.27%, SD 10.79% vs mean 31.56%, SD 16.92%; P=.001; ES: 1.53; clavicular head: mean 53.75%, SD 13.01% vs mean 37.95%, SD 14.67%; P=.006; ES: 1.14). These results suggest that exergaming may be more effective for targeted muscle activation. In conclusion, HIIT can increase muscle activation in the upper extremities and can be incorporated into exergaming strategies to provide a fun and engaging way to exercise.

Sleep-push movement performance in elite field hockey champions with and without training specialization.

To investigate kinematic and muscle activity differences during the sleep-push movement in elite field hockey players. We hypothesized that players with specialized sleep-push movement training (specialists) would possess a lower center of mass (CoM) and enhanced reproducibility of muscle activations during the movement, compared to players without explicit movement training (non-specialists). Ten field hockey players of the Belgian national field hockey team performed the sleep-push movement (5 specialists and 5 non-specialists). Muscle activity and kinematic data were recorded using EMG to evaluate the reproducibility of muscle activations by cross-correlation analysis and power spectral features across the movement, while a motion capture system was used to assess kinematics. Compared to non-specialists, specialists had significantly (p < 0.05) increased stick velocity (9.17 ± 1.28 m/s versus 6.98 ± 0.97 m/s) and lower CoM height (141 ± 52 mm versus 296 ± 64 mm), during the second part of the shot. Specialists also showed a significant (p < 0.05) lower power spectrum in the activity of the upper limb muscles before the shot. Superimposition of the auto crosscorrelation results demonstrated a high degree of reproducibility in specialists' muscle activations. Sleep-push movements realized by elite players who are specialists in the sleep-push movement presented significant kinematics and muscular activation differences when compared to the sleep-push movements realized by elite players who were not specialists in such movement. Characterization of the specific movement and the related high-level performer's muscular strategies offers the possibility of translating sport science findings into functional training with concrete applications for coaches, players, and other key stakeholders for the continued development of the field.

Upper Extremity Electromyography During Bouldering: Research Report

Background: Despite the growing popularity of bouldering, little is known about the degree and variabilityof muscle activation that occurs while solving bouldering problems. The purpose of this study was to explorethe electromyography of eight upper extremity and trunk muscles during a session of indoor bouldering whilecompleting four different problems.Methods: Eleven climbers with self-reported ability to climb a V-scale V4 problem grade or higher and regularlyboulder at least two days/week for at least six months participated in this study. Electromyography was used torecord muscle activity of the flexor digitorum superficialis, extensor carpi radialis longus, biceps brachii, tricepsbrachii, anterior deltoid, middle deltoid, posterior deltoid, and latissimus dorsi.Conclusion: The highest average EMG across all four climbs occurred in the flexor digitorum superficialis,latissimus dorsi, and extensor carpi radialis brevis. Significant differences in muscle activity were noted betweenthe anterior deltoid and latissimus dorsi, flexor digitorum superficialis and biceps brachii, triceps brachii andflexor digitorum superficialis, posterior deltoid and latissimus dorsi, and triceps brachii and latissimus dorsi.This information may be useful in developing a strength and conditioning program for

Poster 103: Proximal Shoulder Muscle Recruitment with Blood Flow Restriction Exercise Under Various Occlusion Conditions: Is More Pressure Really Better?

Objectives: Blood Flow Restriction (BFR) training provides partial occlusion at the proximal upper and lower extremities and has been shown to improve muscular strength and hypertrophy following an injury or surgery. By eliciting hypoxic intramuscular conditions, we can stimulate adaptive processes in skeletal muscle in a similar manner to high intensity resistance training but at substantially lower and safer exercise workloads (20-30%1RM). While much of the literature has focused on tissues distal to the site of occlusion, recent findings (Lambert et al 2021, Bowman et al 2020) have observed proximal benefits (increased muscle mass, work capacity, and performance) to upper extremity BFR in the shoulder region during rotator cuff training in both general population adults and pitching athletes. These findings were partially attributed to increased muscle activation (via electromyography, EMG) observed while extremities were under occlusion. However, only one standardized occlusion pressure (50%LOP) was utilized during these investigations as typical in current literature. The purpose of the present study was to compare muscle activation (EMG amplitude, EMGa) of the shoulder region during BFR training at variable occlusion pressures in order to optimize application and muscle-specific targeting of BFR for rehabilitation and preventative shoulder training. Methods: Institutional review board approval was first obtained. Fifteen healthy subjects (7 males and 8 females; age 29.4 ± 4.26 y.o.) from a sports medicine physical therapy clinic were recruited and consented to participate in this study. Individuals were excluded if they had any pre-existing shoulder pathology in the dominant limb, active participation in a structured upper body weight regimen, or any history of vascular compromise that may render use of BFR inappropriate. Each participant underwent 4 different experimental sessions, which included performing 3 common exercises for the shoulder to failure on the dominant limb; dumbbell scaption, cable external rotation (ER) @ 0°, and cable internal rotation (IR) @ 0°. Exercises were completed with BFR using an automated tourniquet system (Delfi Medical Innovations®) at a different pre-assigned occlusion pressure (0, 25, 50, 75% LOP) each session. Load was determined using 20% of a one-repetition maximum (1RM) for each exercise utilizing a maximal voluntary isometric contraction (MVIC) test. EMGa data utilizing surface electrodes (Delsys, Natick, MA, US) were recorded from target shoulder muscles proximal to the occlusive cuff during testing - anterior deltoid, middle deltoid, posterior deltoid, infraspinatus, teres minor, and upper trapezius muscles. Repetitions to failure (RTF) and assessments of discomfort (VAS, 0-10) with each exercise at the various occlusive pressures were also collected for analysis. Raw EMGa measures were averaged across the first 30 contractions for IR and scaption as well as the first 20 contractions for ER following normalization to 5 calibration contractions at 0% LOP. A mixed model ANOVA repeated on occlusion pressure was performed followed by a Bonferroni post hoc test for pairwise comparisons. Type I error set at ∝=0.05. Results: EMG findings are presented in Figure 1 demonstrating a significant effect of occlusion level on shoulder muscle activation for all exercises (p&lt;0.05). Of note, continued significant increases in EMGa were not observed above 50%LOP with the exception of the teres minor during IR (Figure 1A) or the posterior deltoid during scaption (Figure 1C). As shown in Figure 2, significant decreases in repetitions to failure relative to 0%LOP were observed at 75%LOP for all exercises as well as at 50%LOP for scaption (p&lt;0.05). Also shown in Table 1, a linear increase in discomfort was observed for all exercises with increasing LOP (p&lt;0.01). Conclusions: There appears to be several distinct differences in muscle activation about the shoulder complex based on the exercise as well as occlusive pressure; including a common trend of heightened EMG activity being concurrent with an increase in LOP. These findings may indicate that added occlusion leads to greater muscle utilization, enhancing exercise selection and prescription dependent on the targeted muscle group. However, based on these data, there may be an element of diminishing returns past 50% LOP for the exercises and musculature studied, ultimately limiting efficacy past this occlusion stimulus when considering discomfort or total achievable exercise volume. While limited to the population study, these findings paired with those found in general and athletic populations may be used to establish BFR guidelines which may be suitable for shoulder rehabilitation or injury prevention.

Comparison of Muscle Activation During Toes to Bar Movement Performed with Different Techniques

With the increasing importance of physical fitness in the world, physical activity types such as CrossFit, which includes high-intensity combined movements, have become popular. The aim of this study was to compare the rectus abdominis (RA) muscle activation during the kipping toes-to-bar (KTB) and the strict toes-to-bar (STB) movements. RA muscle activation was measured during the KTB and STB exercises in 12 healthy young men. Participants performed 5 repetitions of both KTB and STB exercises in randomized order. Participants performed both exercises with a 5-minute rest interval. For comparing the RA muscle activity during the KTB and STB paired sample t-test was used. A significant difference was found between the KTB (359.56 ± 160.50 μV) and the STB (415.37 ± 185.63 μV) for RA muscle activation (p&amp;lt;0.05). These findings demonstrated that the difference in RA muscle activity during the STB and KTB movements showcases the importance of the STB movement on the RA that revealed greater motor units’ activation in a non-oscillation position. The study finding emerges that the same exercise can lead to different motor unit activations in the same muscle group, depending on the way the movement is performed.

Evaluating Gait Stability and Muscle Activation in Different Hand Holding Conditions Using the Robotic Walker-mTPAD.

While walkers are used as mobility aids for different gait impairments, little is known about the factors that affect the performance of such aids. Therefore, we investigated the impact of arm-holding conditions on gait stability and muscle activation. We used surface electromyography (sEMG) sensors on specific arm and leg muscles while the users took laps with a robotic walker, the mobile Tethered Pelvic Assist Device (mTPAD), on an instrumented mat. Eleven participants without gait disorders walked with and without a 10% body weight (BW) force applied on the pelvis in the following three configurations: (i) while gripping the walker's frame, (ii) while using an armrest with their arms at a 90∘ angle, and (iii) while using an armrest with their arms at a 130∘ angle for 5 min each. Our results showed that when applying a force, the users changed their gait to increase stability. We also discovered differences in muscle activation based on the user's specific arm conditions. Specifically, the 130∘ condition required the least muscle activation, while gripping the walker's frame increased specific muscle activation compared to 90∘ and 130∘. This study is the first to evaluate how arm-holding and external loading conditions alter gait and muscle activations using the mTPAD.

Muscle Coactivation Index during Walking in People with Multiple Sclerosis with Mild Disability, a Cross-Sectional Study.

Multiple sclerosis (MS) is a progressive neurodegenerative disease characterized by axonal degeneration and demyelination. Changes in gait, related to joint kinematics and kinetics, especially at the ankle and knee, have been observed in people with MS (pwMS). Muscle coactivation plays an important role in joint stabilization; however, excessive coactivation may interfere with gait. The aim of this study was to analyze the differences in muscle activation during gait in pwMS compared to healthy individuals. A cross-sectional study was conducted involving pwMS and healthy controls. Surface electromyography was used to record muscle activity during gait. The main outcome measures were the coactivation index (CI) and the area under the curve (AUC), which were calculated for several pairs of lower extremity muscles. Nine pwMS and nine healthy controls were included. When comparing the MS group to the control group, the AUC was significantly higher in the lateral gastrocnemius (p = 0.023) and the CI for the lateral gastrocnemius-anterior tibialis (p = 0.022) and gluteus maximus-lateral gastrocnemius (p = 0.047). Mildly affected pwMS have altered muscle coactivation patterns during gait, especially in the most affected limb. The results highlight the importance of muscle coactivation in pwMS and its possible role in the early detection of gait abnormalities.

1634-P: Brown Adipose Tissue and Muscle Responses to Tolerable Cold in Black and White Young Lean Men

There has been a renewed interest in brown adipose tissue (BAT) as a therapeutic target for diabetes and obesity treatments due to its ability to consume glucose and expend energy in response to cold temperatures and Beta-adrenergic stimulation. However, comparisons of BAT in different races are limited. To address this knowledge gap, we directly compared healthy, young, lean Black and White men in a controlled inpatient study using a whole-room indirect calorimeter. 12 Black and 12 White men completed a 6-13-day protocol with randomized calorimeter temperatures between 18-31°C for 5 hours. Resting metabolic rate (RMR) was measured under reclined, fasted conditions with standard clothing. Body composition was measured by dual x-ray absorptiometry and BAT and muscle glucose uptake activity was quantified using 18-F Fluorodeoxyglucose (18-F FDG) PET-CT following the last chamber study where each individual's coldest tolerable temperature (Tct) was used. Basal metabolic rate (BMR) was defined as minimum RMR and the cold-induced thermogenesis (CIT) was calculated as the percentage increase of RMR above BMR in the cold. The groups were similar in age (23.8±4.7 yrs) and BMI (23.1±1.5 kg/m2) and their Tct (21.0±1.4°C; p=0.54) and CIT (12.1±8.1 kcal/h; p=0.8) were not different. While White males had significantly higher BAT volume (334 ± 188mL vs 242 ± 89mL; p=0.045), BAT volume was comparable between the groups after normalizing to body volume. BAT activity was similar between the groups. Among all muscle activity measured, the intercostal muscles in the Black males had significantly higher activity (p=0.002) and activity was present in all 12 Black participants but only 4 of 12 White males. Individual BAT or muscle activity did not correlate with each other nor with Tct or CIT. Our data suggest that the cold-induced BAT activity was comparable in Black and White young, lean men. The surprising difference in intercostal muscle activity warrants further investigation. Disclosure R.J.Thomas: None. R.Brychta: None. A.B.Courville: None. S.Mcgehee: None. A.M.Cypess: None. K.Y.Chen: None.

Differences in Muscle Activity and Mouse Behavior Data of Graphic Design Workers in Moving and Dragging Tasks with Different Targets

Over time, repeated mouse-dragging manipulation may cause discomfort in the upper extremities. This study compared biomechanical parameters, mouse movement data, and the discomfort perception index between 2-min mouse dragging and moving manipulation tasks with higher or normal target objectives. We recruited 20 non-symptomatic graphic design students who frequently engage in intensive mouse-dragging manipulation. We assessed the impact of continued dragging versus non-dragging manipulation using electromyographic data, mouse fingertip pressure data, and mouse trajectory velocity data. We also performed a temporal correlation analysis between EMG, mouse velocity, and fingertip pressure to investigate the relationship between physiological data and mouse movement performance. The study revealed significant differences between the dragging and moving tasks regarding muscle activity, mouse velocity, and fingertip pressure. In particular, the percentage of muscle activation on the right side of the extensor carpi radialis longus (ECR) and the lateral head of the triceps brachii (TB) differed significantly between the two tasks, with higher muscle activation levels during the dragging task. Moreover, the average muscle activation of ECR and TB was significantly higher at high target operation levels. In addition, the study revealed that the horizontal, vertical, and mean mouse velocities were significantly higher for the dragging manipulation in the high target task than for the mouse moving manipulation. In the temporal correlation analysis, the correlation coefficients of muscle activation, fingertip pressure, and mouse mean velocity differed between the two mouse manipulation behaviors, with a higher correlation between muscle activation levels and pressure values during the dragging manipulation.

Riding a Mechanical Scooter from the Inconvenient Side Promotes Muscular Balance Development in Children

Mechanical scooter riding is a popular physical activity among children, but little is known about the differences in muscle loading between the dominant and non-dominant sides during this activity. The objective of this study was to identify the muscle activation patterns in children’s dominant and non-dominant legs as they rode scooters on the convenient and inconvenient sides. The study included nine healthy children aged 6–8. The participants rode 20 m on a mechanical scooter at a self-selected pace using both the convenient and inconvenient sides. Electromyography was used to measure the muscle activity in the dominant and non-dominant legs during the pushing and gliding phases. A 20 m sprint run was used as a control exercise to estimate the typical differences in muscle activation between the dominant and non-dominant legs. In the pushing phase, the symmetry index for five of the eight analyzed muscles exceeded 50% (p &lt; 0.05); four of these muscles were more active in the pushing leg, and one was more active in the standing leg. In the gliding phase, four muscles were more active in the standing leg, and one was more active in the pushing leg (p &lt; 0.05). Upon observing children who changed sides while riding a scooter, it was found that the pattern of muscle activation displayed a reverse trend that resembled the initial pattern. Our study indicated notable differences in muscle activity patterns between the dominant and non-dominant sides of individual leg muscles during children’s scooter riding. These patterns were reversed when children switched sides on the scooter. These findings suggest that using both legs and switching sides while riding a scooter may be a viable strategy for promoting balanced muscular development.

The effect of EMG biofeedback training on muscle activation in an impingement population

Subacromial impingement syndrome (SAIS) is one of the most diagnosed causes of pain in the upper extremity. The purpose of this study was to investigate muscle activity between asymptomatic and SAIS shoulders on the same subject while understanding the effectiveness of EMG biofeedback training (EBFB) on bilateral overhead movements. Ten participants (7 male), that tested positive for 2/3 SAIS clinical tests, volunteered for the study. Bilateral muscle activity was measured via electrodes on the upper trapezius (UT), lower trapezius (LT), serratus anterior (SA), and lumbar paraspinals (LP). Participants performed bilateral scapular plane overhead movements before and after EBFB. EBFB consisted of 10 bilateral repetitions of I, W, T, and Y exercises focused on reducing UT and increasing LT and SA activity. Prior to EBFB, no significant difference in muscle activity was present between sides. A significant main effect of time indicated that after EBFB both sides exhibited reduced UT activity at 60° (p=0.003) and 90° (p=0.036), LT activity was increased at all measured humeral angles (p<0.0005), and SA muscle activity was increased at 110° (p=0.001). EBFB in conjunction with scapular based exercise effectively alters muscle activity of asymptomatic and symptomatic scapular musculature.