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Humans experience unanticipated external postural perturbations and recover their posture faster via involuntary responses than voluntary responses. Previous cross-sectional comparisons between athletes and untrained populations have suggested that daily motor experiences can lead to adaptations in the reftex system, but the temporal aspect of this adaptation has been unclear. Here we show that judokas have an earlier muscle activation response to even non-judo-specific external perturbations compared with an untrained population. The response latency to a backward push-and-release type postural perturbation was compared between male judokas (n = 7. career >13 years. ranging from world champions to prefectural competitors) and untrained nonjudokas (n = 7). Latency was defined as the instant of tibialis anterior muscle activity onset. Judokas exhibited shorter latency (20.6 ± 7.1 ms) than nonjudokas (28.3 ± 8.9 ms). The rank order of latency in judokas did not correlate with their competition performance. We suggest that daily training in responding to perturbations might improve some parts of the sensorimotor pathway relating to postural response latency, and that this excellence in involuntary response is independent of athletic performance. The findings provide a novel perspective for understanding postural control ability in humans. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the effectiveness of a focal vibration protocol added to an activation protocol with active muscle contractions and to see what repercussions it has on sprint, countermovement jump (CMJ), and lower limb isometric strength. A double‐blind randomized clinical trial was conducted in the Functional Anatomy Laboratory and the sample consisted of 70 athletes. The main outcome measures were knee extension force, CMJ, sprint, and surface electromyography. Repeated‐measures analysis of variance revealed significant improvements. They were found in the within‐group analysis for the Experimental Group in the isometric extension force (p < 0.001; η2 = 0.368), CMJ (p < 0.001; η2 = 0.301) and 30 m sprint (p < 0.001; η2 = 0.376). In the electromyography, there are changes in the Sham Group in all muscles, in CMJ and Sprint tests, and no differences in the Experimental Group, except for the RF muscle. In the between‐group analysis, statistically significant differences were found only in favor of the Experimental Group in CMJ (p = 0.017; η2 = 0.81) and 30 m sprint (p < 0.001; η2 = 0.152). These results confirm a significant improvement in the sprint, CMJ performance, and quadriceps strength, after a focal vibration protocol, added to a muscle active contraction, compared to a focal vibration sham protocol. Therefore, our results suggest that the focal vibration can be a very useful tool in sports involving high‐powered actions. [ABSTRACT FROM AUTHOR]

Investigate the effect of surface on frontal plane knee angle, knee moment and muscle activity. Randomised cross over. University Laboratory. Twenty females performed single-leg hop-landings onto sand, grass and firm surfaces. Kinematic, kinetic and muscle activity data were obtained. Compatibility curves were used to visualise parameter estimates alongside P - values, and S-value transforms. Knee angle for firm-sand (mean difference (d) ‾ = −2.2°; 95% compatibility interval (CI): −4.6 to 0.28, p = 0.083, s = 3.6) and firm-grass ( d ‾ = −1.9; 95% CI: −4.3 to 0.5, p = 0.125, S = 3) yielded <4 bits of reputational information against the null hypothesis (H). 5 bits (p = 0.025) of information against H were observed for knee moment between firm-sand ( d ‾ = 0.17 N m/kg-1. m-1; 95% CI: 0.02 to 0.31) with similar effects for firm-grass ( d ‾ = 0.14 N m/kg-1. m-1; 95% CI: −0.02 to 0.29, p = 0.055, S = 4). Muscle activity across surfaces ranged from almost no (S = 1) reputational evidence against H (Quadriceps and Hamstrings) to 10–13 'bits' against H for lateral gastrocnemius (lower on sand). Our study provides valuable information for practitioners of the observed effect sizes for lower-limb landing mechanics across surfaces in asymptomatic females. • Knee abduction moment was reduced in females on both sand and grass surfaces compared to firm. • Peak vertical ground reaction force was reduced on sand compared to a grass and firm surface. • Lateral gastrocnemius activation was reduced on sand compared to grass and firm surfaces. • VL, VM, LH and MH activation was similar when landing on sand, grass and firm surfaces. [ABSTRACT FROM AUTHOR]

A passive-control foot press trainer (PFPT) based on spring resistance aims to strengthen the ankle joint, similar to heel raise exercise (HRE). To compare the muscle activity of the tibialis anterior, gastrocnemius medialis, gastrocnemius lateralis, rectus femoris, and biceps femoris between PFPT and HRE. Eight healthy women performed four exercise conditions: PFPT forefoot (PFPT FF), PFPT rearfoot (PFPT RF), HRE at the floor level (HRE F), and HRE on the block (HRE B). During exercise, muscle activity was measured using surface electromyography and subsequently converted to percentages of maximum voluntary isometric contraction. Tibialis anterior showed the highest activity in PFPT FF, with significant difference from other conditions. Gastrocnemius medialis and lateralis demonstrated the highest activity in HRE B; Rectus femoris showed the highest activity in PFPT RF, showing significant differences from other conditions (p< 0.05). Biceps femoris exhibited the highest activity in HRE F and a significant difference from PFPT FF and PFPT RF. Lower leg and thigh muscle activity between PFPT and HRE had similarities and differences. Future studies should analyze the long-term effects of PFPT, including on patients with musculoskeletal and nervous system injuries. [ABSTRACT FROM AUTHOR]

With expertise, athletes develop motor strategies that enhance sports performance or reduce functional costs. Motor variability is known as a relevant way to characterize these strategies in athletes with different levels of expertise. The aim of this scoping review is to gather and discuss the latest advances in the impact of expertise on motor variability during sports‐related tasks. A search encompassing three databases, Medline, SportDiscus, and Academic Search Complete, was performed. Our research methodology included three core themes: motor variability, laboratory instruments, and sports. Motor variability metrics (e.g., standard deviation and approximate entropy) and laboratory instruments (e.g., motion capture system, EMG, and force plate) were compiled. Athletes' expertise was defined by the time of deliberate practice, the performance results, or the level in which they performed. Overall, 48 of the 59 included studies determined that higher‐skilled athletes had lesser motor variability than lower‐skilled athletes. This difference in motor variability between skill levels was present within individual athletes (intra‐individual) and between athletes (inter‐individual). This result was independent of the criteria used to define expertise, the type of instrumentation used, and the metrics used to quantify motor variability. [ABSTRACT FROM AUTHOR]

The objective of this study was to assess the efficacy and user's impression of an arm-support exoskeleton in complex and realistic ceiling construction tasks. 11 construction workers performed 9 tasks. We determined objective and subjective efficacy of the exoskeleton by measuring shoulder muscle activity and perceived exertion. User's impression was assessed by questionnaires on expected support, perceived support, perceived hindrance and future intention to use the exoskeleton. Wearing the exoskeleton yielded persistent reductions in shoulder muscle activity of up to 58% and decreased perceived exertion. Participants reported limited perceived hindrance by the exoskeleton, as also indicated by no increase in antagonistic muscle activity. The findings demonstrate the high potential of an arm-support exoskeleton for unloading the shoulder muscles when used in the dynamic and versatile working environment of a ceiling construction worker, which is in line with the consistent intention of the workers to use the exoskeleton in the future. Practitioner Summary: The majority of research focuses on the effect of using an arm-support exoskeleton during isolated postures and prescribed movements. We investigated the efficacy of an exoskeleton during a complex and realistic work, namely ceiling construction. Shoulder muscle activity was lower in almost all tasks when wearing the exoskeleton. [ABSTRACT FROM AUTHOR]

Introduction: Tasks performed at or above head height in industrial workplaces pose a significant challenge due to their association with musculoskeletal disorders. Upper-body exoskeletons have been identified as a potential solution for mitigating musculoskeletal loads and fighting against excessive muscular fatigue. However, the influence of such support on fine motor control, as well as on cognitive-motor interference, has received limited attention thus far. Therefore, this crossover randomized study aimed to investigate the impact of the use of a passive upper-body exoskeleton in the presence of muscular fatigue or not. Additionally, focusing on differences between single (ST) and dual (DT) industrial tasks consisting of overhead speed and accuracy exercises. Methods: In both scenarios, N = 10 participants (5 male/5 female) engaged in an overhead precision task using a nail gun to precisely target specific areas on three differently sized regions, based on Fitts' law paradigm (speed-accuracy trade-off task). This was done with and without the passive upper-body exoskeleton, before and immediately after a fatiguing exercise of shoulder and leg muscles. In addition, a second task (dual-task, DT) was carried out in which the occurrence of an auditory signal had to be counted. The main outcomes were muscular activation of the shoulder girdle as well as the time to perform speed-accuracy tasks of different difficulty indexes (calculated by means of Fitts' law). Results and discussion: In the absence of fatigue, the exoskeleton did not affect the speed-accuracy trade-off management of participants in the single task, but it did in the dual-task conditions. However, after muscle fatigue, the speedaccuracy trade-off was differently affected when comparing its execution with or without the exoskeleton. In general, the dual task resulted in longer times to perform the different tasks, whether it was with or without the exoskeleton. Furthermore, the use of the exoskeleton decreased muscle activity, which is associated with less physical effort, but only significantly for the M. deltoideus and M. trapezius when compared by tasks. Overall, these study findings highlight the potential supportive effects of using an upper-body exoskeleton for industrial overhead tasks. [ABSTRACT FROM AUTHOR]

Previous studies examining the flexion–relaxation phenomenon (FRP) in back muscles through trunk forward flexion tests have yielded inconsistent findings, primarily due to variations in leg posture control. This study aimed to explore the influence of leg posture control and individual flexibility on FRP in back and low limb muscles. Thirty-two male participants, evenly distributed into high- and low-flexibility groups, were recruited. Activities of the erector spinae, biceps femoris, and gastrocnemius muscles, alongside the lumbosacral angle (LSA), were recorded as participants executed trunk flexion from 0° to 90° in 15° increments, enabling an analysis of FRP and its correlation with the investigated variables. The findings highlighted significant effects of all examined factors on the measured responses. At a trunk flexion angle of 60°, the influence of leg posture and flexibility on erector spinae activities was particularly pronounced. Participants with limited flexibility exhibited the most prominent FRP under constrained leg posture, while those with greater flexibility and unconstrained leg posture displayed the least FRP, indicated by their relatively larger LSAs. Under constrained leg posture conditions, participants experienced an approximate 1/3 to 1/2 increase in gastrocnemius activity throughout trunk flexion from 30° to 90°, while biceps femoris activity remained relatively constant. Using an inappropriate leg posture during back muscle FRP assessments can overestimate FRP. These findings offer guidance for designing future FRP research protocols. [ABSTRACT FROM AUTHOR]

INTRODUCTION: Virtual reality (VR) holds promise for stroke rehabilitation. However, many existing VR systems requires users to stand while playing, posing a potential falling risk for stroke patients. This study investigated the effects of a custom-developed VR system that focus on trunk rehabilitation in stable sitting position on muscle activities, postural control, and physiological cost compared to conventional trunk exercises in stroke patients. MATERIALS AND METHODS: A cross-sectional observational pilot study was conducted involving 12 paretic stroke subjects performing four exercises: two Conventional Trunk Exercises (CTE) and two VR-based Trunk Exercises (VRTE) using customized Tilt-The-Maze (self-paced) or Catch-The-Mole (game-paced) games. Muscle activity was measured using electromyography (EMG). Postural control data in the Anterior-Posterior (AP) and Medio-Lateral (ML) axes was recorded using a force plate, while the physiological cost was measured via a heart rate sensor during the exercises. RESULTS: The results indicated low muscle activity and light -intensity cardiovascular responses in all CTE and VRTE exercises. Game-paced VRTE recorded slightly higher Center of Pressure (CoP) velocity in the AP and ML axes versus CTE (AP:4.40±1.80 vs. 4.02±1.20 cm/s; ML:6.40±2.54 vs. 5.42±2.21 cm/s). In contrast, the self-paced VRTE showed an insignificant impact on postural control than both CTE and game-paced VRTE. CONCLUSION: The game-paced VRTE induced comparable effects on muscular activation, postural control, and physiological cost to that of CTE in stroke patients. The findings suggest the stable-sitting VR system as a supplementary approach to the existing trunk rehabilitation protocols for stroke patients. [ABSTRACT FROM AUTHOR]

Objective: Knowing the morphological, kinematic, and electrophysiological parameters of the smile in healthy individuals may contribute to evaluating, planning, and monitoring the smile reanimation. This study aimed to determine the correlation between 3D morphometric changes, movement kinematics, and muscle activity in the facial soft tissue of healthy individuals. Method: In this cohort study, 20 volunteers were selected from healthy individuals with no facial disorders. During smiling, three‐dimensional face scanning, facial motion capture, and surface electromyography (sEMG) were performed. The average displacement, velocity, and acceleration during facial movements were measured. The mean change in 3D surface morphometry and activation of the zygomaticus major were determined. Results: The volunteers, comprising 10 males and 10 females, had a mean age of 24 ± 10 years; for female, mean age was 23 ± 5 years and for men 26 ± 13 years. Significant correlations were found between kinematic and morphometric data (r = 0.51, p < 0.001), sEMG and morphometric (r = 0.50, p < 0.001) data, and sEMG and kinematic data (r = 0.49, p < 0.002). The maximum acceleration occurred during approximately 65% of the muscle activation time and 64% of the peak muscle activation value. Additionally, the maximum velocity was reached at around 73% of the muscle activation time and 67% of the peak muscle activation value. Furthermore, the maximum displacement values were observed at approximately 88% of the muscle activation time and 76% of the peak muscle activation value. Conclusion: The findings may provide insights into the smile's functional parameters, contribute to understanding facial muscle‐related disorders, and aid in improving the diagnosis and treatment of the smile. Level of Evidence: NA Laryngoscope, 134:3112–3119, 2024 [ABSTRACT FROM AUTHOR]

This study recruited 30 young participants (15 men and 15 women) to examine the smartphone usage patterns in three postures (standing, supported sitting, and unsupported sitting) and at five head angle (HA) positions (0°-40°). Cervical erector spinae (CES) and upper trapezius (UTZ) muscle activity, neck flexion (NF), gaze angle (GA), viewing distance (VD), and discomfort scores were collected. Results showed that HA and posture almost affected all responses, while CES muscle activity, NF, and VD differed between sexes. Strain in the neck and shoulder region increased with HA increase. Particularly, when the HA exceeded 20°, the discomfort scores considerably increased. Unsupported sitting should be avoided during smartphone use because of relatively poor responses in all variables. However, both standing and supported sitting have their respective benefits. Sex-related differences were typically observed in the standing position, with women tending to have lower NF but higher CES muscle activity compared with men. Practitioner summary: Although smartphones have become daily necessities, the overall quantitative neck and shoulder strain of using smartphones in different postures is rarely evaluated. We suggest that maintaining the HA within 20° is recommended because of relatively low load on the neck and shoulders. An unsupported sitting should be avoided during smartphone use. [ABSTRACT FROM AUTHOR]

Context: In athletes, postural control impairment and knee muscle dysfunction are the most common disorders following anterior cruciate ligament (ACL) injury. Because of functional changes in the motor cortex following ACL injury, physiotherapy (PT) is not enough for treatment and using neuromodulators, such as trans-cranial direct current stimulation (tDCS) may be necessary. The present study focused on the effects of anodal tDCS (a-tDCS) over the primary motor cortex (M1) concurrent with PT on postural control and muscular performance in the athletes with ACL injury. Design: In this study, 34 athletes with ACL injury were randomly assigned in 2 groups of intervention group (active M1 a-tDCS concurrent with PT, n = 16) and control group (sham M1 a-tDCS concurrent with PT, n = 16). Methods: The participants of all groups received 20-minute 2 mA M1 a-tDCS with PT during 10 sessions, while tDCS was turned off after 30 seconds in the sham group. Before, immediately following, and 1 month after the interventions, the center of pressure and the average of power of flexor and extensor muscles at 2 velocities of 30°/s and 60°/s were measured by force plate and isokinetic devices, respectively. Results: One month after treatment, the displacement of center of pressure was decreased in the intervention group (P < .05), while there were no changes in the control group. Y-axis of center of pressure decreased in the intervention group relative to the control group, although average of power of flexor and extensor muscles increased immediately in both groups, but the rise in the intervention group was larger than that in the control group (P < .05). Conclusion: The findings indicated that M1 a-tDCS can induce the efficacy of PT, which has a lasting effect on the improvement of the postural control in athletes with ACL injury. [ABSTRACT FROM AUTHOR]

Abstract Women frequently express heightened neck discomfort even though they exhibit smaller neck flexion (NF) during smartphone use. Differences in natural posture while using smartphones may result in varying muscle activation patterns between genders. However, no study focused on this issue. This study investigated the influence of gender on neck muscle activity and NF when using smartphones, ranging from slight (20°) to nearly maximal forward head flexion, across different postures. We analyzed smartphone usage patterns in 16 men and 16 women and examined these behaviors across different scenarios: standing, supported sitting, and unsupported sitting, at 20°, 30°, 40°, and the maximum head angles. During data collection, muscle activity was measured, expressed as a percentage of the maximum voluntary contraction (%MVC), in the cervical erector spinae (CES) and upper trapezius (UTZ), along with NF. Results show significant influences of gender, head angle, and posture on all measures, with notable interactions among these variables. Women displayed higher muscle activities in CES and UTZ, yet exhibited lesser NF, while using smartphones in both standing (12.3%MVC, 10.7% MVC, and 69.0°, respectively) and unsupported sitting (10.8%MVC, 12.3%MVC, and 71.8°, respectively) compared to men (standing: 9.5%MVC, 8.8%MVC, and 76.1°; unsupported sitting: 9.7%MVC, 10.8%MVC, and 76.1°). This study provides a potential rationale for gender-related disparities in injury outcomes, emphasizing that women experience higher neck and shoulder discomfort level, despite their smaller NF during smartphone use, as found in previous research. Additionally, the cervical flexion-relaxation phenomenon may occur when the head angle exceeded 40°. The near-maximum head angle during smartphone use might induce the cervical flexion-relaxation phenomenon, potentially aggravating neck issues. We recommend limiting smartphone usage postures that exceed the near-maximum head angle, as they are commonly adopted by individuals in the daily smartphone activities.

OBJECTIVES Thigh strength has many features in our life. Many people perform vary squat types to stimulate different thigh muscles. However, there is a lack of information on which squat is the most effective on targeted muscles. Therefore, the purpose of this study was to compare thigh muscles’ activity by squat types and suggest the correct squat for strengthening thigh. METHODS Total of 20 men and women (age: 23.9±1.5yrs, height: 173.3±6.6cm, weight: 75.1±13.2kg, BMI: 24.9±3.1kg/m2) who had no musculoskeletal pathologies within last one year, and had weight training experience for more than 1 year were participated. Squat types were classified into standard (SS), narrow (NS), wide (WS), jump (JS), and Smith machine squats (SMS). Surface electromyography was used to collect the muscle activity of the thigh during three repetitions of each squat without weights. Time points during squat are defined as follows: E1 (start), E2 (maximum knee flexion, MKF), E3 (returned), P1 (from start to MKF), and P2 (from MKF to return). Repeated measured ANOVA was used to verify differences in lower limb muscle activity between squat types. RESULTS At the E2, significant differences were found in RF (p=.00) and ST (p=.00). In the P1, significant differences were found in RF (p=.00), VL (p=.00), and BF (p=.02). In the P2, significant differences were found in RF (p=.00), VM (p=.00), and ST (p=.01). CONCLUSIONS For more activity of both quadriceps and hamstrings, plyometric-based JS is the most effective squat, but by considering the performer's lack of exercise experience, postural control may not be performed correctly which may lead to injury. In addition, stable squat using the Smith machine should be considered and the intensity, number of repetitions, and weight should be carefully set according to type of squat.

BACKGROUND: This study aims to implement a set of wearable technologies to record and analyze the surgeon's physiological and ergonomic parameters during the performance of conventional and robotic-assisted laparoscopic surgery, comparing the ergonomics and stress levels of surgeons during surgical procedures. METHODS: This study was organized in two different settings: simulator tasks and experimental model surgical procedures. The participating surgeons performed the tasks and surgical procedures in both laparoscopic and robotic-assisted surgery in a randomized fashion. Different wearable technologies were used to record the surgeons' posture, muscle activity, electrodermal activity and electrocardiography signal during the surgical practice. RESULTS: The simulator study involved six surgeons: three experienced (>100 laparoscopic procedures performed; 36.33 ± 13.65 years old) and three novices (<100 laparoscopic procedures; 29.33 ± 8.39 years old). Three surgeons of different surgical specialties with experience in laparoscopic surgery (>100 laparoscopic procedures performed; 37.00 ± 5.29 years old), but without experience in surgical robotics, participated in the experimental model study. The participating surgeons showed an increased level of stress during the robotic-assisted surgical procedures. Overall, improved surgeon posture was obtained during robotic-assisted surgery, with a reduction in localized muscle fatigue. CONCLUSIONS: A set of wearable technologies was implemented to measure and analyze surgeon physiological and ergonomic parameters. Robotic-assisted procedures showed better ergonomic outcomes for the surgeon compared to conventional laparoscopic surgery. Ergonomic analysis allows us to optimize surgeon performance and improve surgical training. [ABSTRACT FROM AUTHOR]

Monitoring physical demands during task execution with exoskeletons can be instrumental in understanding their suitability for industrial tasks. This study aimed at developing a fatigue level prediction model for Back-Support Industrial Exoskeletons (BSIEs) using wearable sensors. Fourteen participants performed a set of intermittent trunk-flexion task cycles consisting of static, sustained, and dynamic activities, until they reached medium-high fatigue levels, while wearing BSIEs. Three classification algorithms, Support Vector Machine (SVM), Random Forest (RF), and XGBoost (XGB), were implemented to predict perceived fatigue level in the back and leg regions using features from four wearable wireless Electromyography (EMG) sensors with integrated Inertial Measurement Units (IMUs). We examined the best grouping and sensor combinations by comparing prediction performance. The findings showed best performance in binary classification of leg and back fatigue with 95% (2 EMG + IMU sensors) and 82% (single IMU sensor) accuracy, respectively. Tertiary classification for back and leg fatigue level prediction required four sensor setups with both EMG and IMU measures to perform at 79% and 67% accuracy, respectively. The efforts presented in our article demonstrate the feasibility of an accessible fatigue level detection system, which can be beneficial for objective fatigue assessment, design selection, and implementation of BSIEs in real-world scenarios. [ABSTRACT FROM AUTHOR]

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BackgroundObjectiveMethodsResultsConclusionPeople with chronic low back pain (LBP) often demonstrate altered muscle activation with movements that involve the lumbopelvic region and hips.The purpose of this study was to compare gluteus medius activity during sidelying hip abduction (SHA) and sidelying hip abduction-lateral rotation (SHALR) with and without instruction for lumbopelvic stabilization in people with and without chronic LBP.A cross-sectional study was conducted recruiting participants with (n = 17) and without (n = 17) chronic LBP. Gluteus medius activity was recorded with surface electromyography during the performance of SHA and SHALR with and without instructions including the abdominal drawing-in maneuver for lumbopelvic stabilization.For SHA and SHALR, there was a significant main effect for instruction for stabilization indicated by a decrease in gluteus medius activity with instructions (p = .001, p < .001). There was not a significant main effect of chronic LBP on gluteus medius activity between groups for either activity. There was no significant interaction effect of pain and instruction for stabilization with SHA or SHALR.Knowledge of changes in gluteus medius muscle activation patterns with trunk stabilization instruction may help clinicians with assessment of exercise performance to optimize gluteus medius activation. [ABSTRACT FROM AUTHOR]

In everyday life, we recurrently perform two tasks simultaneously, which is called dual-tasking. A common dual task is smartphone use while standing or walking. According to previous studies, this task can compromise postural stability. However, few studies have analyzed lower limb muscle activity during dual-tasking using smartphones. This study aimed to assess the postural sway and muscle activity during dual-tasking in young adults. Thirty-six healthy young adults (23.08 ± 3.92 years) participated in this study. They performed a single task (ST: keeping a quiet standing posture) and a dual task (DT: keeping the ST while simultaneously performing a cognitive task on their smartphone). Postural sway was assessed through the center of pressure (CoP) analysis using a force platform: total CoP displacement, CoP displacement in the anterior–posterior and medial–lateral directions, mean total velocity of the CoP, mean velocity of the CoP in the anterior–posterior and medial–lateral directions, and 95% confidence ellipse sway area. A surface electromyography system recorded the muscle activity of the lumbar spinal erector and five muscles of the lower limb (bilaterally). The results showed an increase in postural sway from the ST to the DT in all CoP variables (p < 0.05), and muscle activity in most muscles analyzed decreased from the ST to the DT (p < 0.05). In conclusion, our results reflect a decentralization of attention from motor performance once postural sway increased and muscle activity decreased in dual-task conditions. [ABSTRACT FROM AUTHOR]

Treadmill running is a common method of exercise and to study human locomotion. Research has examined the kinematics and kinetics of overground and treadmill running, but there has been less focus on the levels of muscle activity during treadmill running. We investigated if muscle activity is different while running overground compared to running on a variety of treadmills. A total of 11 healthy individuals ran at 3 speeds (2.6, 3.6, 4.5 m/s) under 4 different running conditions (3 treadmills, overground). The three treadmills included a typical home exercise treadmill, a midsize commercial research treadmill, and a large, instrumented research treadmill. Surface EMG of the tibialis anterior (TA), gastrocnemius medialis (GM), rectus femoris (RF) and biceps femoris (BF) muscles were measured for each running condition. The integrated EMG was computed for each running condition for the stance and swing phase, as well as 100ms before and after the heel-strike. Friedman analysis revealed significant effects during the stance phase for GM and RF at all speeds, such that muscle activation was lower on the treadmills relative to overground. During the stance phase at faster speeds, themuscle activity was higher for the TA and lower for the BF while running on the different treadmills compared to overground running. Before heel-strike, the TA was significantly less active during treadmill compared to overground running at 2.6 m/s and the RF showed significantly higher activity at 3.6 m/s and 4.5 m/s while running on the different treadmills. Summarizing, differences were mainly observed between the different treadmill conditions relative to overground running. Muscle activation differences between the different treadmill conditions were observed at faster running speeds for RF during the pre-heel-strike phase only. Different types of treadmills with different mechanical properties affects the muscle activity during stance phase as well as in preparation to heel-strike. Additionally, the muscle activity is greater during overground compared to treadmill running during the stance phase for the GM, BF, and RF. [ABSTRACT FROM AUTHOR]

Background: Surface electromyography (sEMG) can provide an objective and quantitative image of the functional state of neuromuscular balance in the stomatognathic system. The objective of this systematic review is to examine current scientific evidence regarding the effects of orthodontic treatment on muscle electromyographic (EMG) activity in children. Methods: The search strategy included the PubMed, PubMed Central, Web of Science, Scopus, and Embase databases. The inclusion criteria were studies assessing EMG muscle activity in children undergoing orthodontic treatment compared with untreated children. The Cochrane risk-of-bias tool (RoB2) and the Newcastle–Ottawa Scale (NOS) were used to evaluate the quality of the studies. The quality of evidence assessment was performed using GRADE analysis. The PRISMA diagram visually represented the search strategy, as well as screening and inclusion process. Results: The search strategy identified 540 potential articles. Fourteen papers met the inclusion criteria. Six studies were judged at a low risk of bias. The certainty of evidence was rated as moderate to low, according to the GRADE criteria. Studies showed alterations in EMG muscle activity in children undergoing orthodontic treatment. Conclusions: Orthodontic treatment appears to affect muscle activity in children undergoing orthodontic treatment. However, the quality of evidence is low and, therefore, it is not possible to definitively state this effect. Further long-term studies are needed to confirm the findings of this review. Study protocol number in PROSPERO database: CRD42023491005. [ABSTRACT FROM AUTHOR]

The efficacy of interrupting prolonged sitting may be influenced by muscle activity patterns. This study examined the effects of interrupting prolonged sitting time with different muscle activity patterns on continuously monitored postprandial glycemic response. Eighteen overweight and obese men (21.0 ± 1.2 years; 28.8 ± 2.2 kg/m2) participated in this randomized four‐arm crossover study, including uninterrupted sitting for 8.5 h (SIT) and interruptions in sitting with matched energy expenditure and duration but varying muscle activity: 30‐min walking at 4 km/h (ONE), sitting with 3‐min walking at 4 km/h (WALK) or squatting (SQUAT) every 45 min for 10 times. Net incremental area under the curve (netiAUC) for glucose was compared between conditions. Quadriceps, hamstring, and gluteal muscles electromyogram (EMG) patterns including averaged muscle EMG amplitude (aEMG) and EMG activity duration were used to predict the effects on glucose netiAUC. Compared with SIT (10.2 mmol/L/h [95%CI 6.3 to 11.7]), glucose netiAUC was lower during sitting interrupted with any countermeasure (ONE 9.2 mmol/L/h [8.0 to 10.4], WALK 7.9 mmol/L/h [6.4 to 9.3], and SQUAT 7.9 mmol/L/h [6.4 to 9.3], all p < 0.05). Furthermore, WALK and SQUAT resulted in a lower glucose netiAUC compared with ONE (both p < 0.05). Only increased aEMG in quadriceps (−0.383 mmol/L/h [−0.581 to −0.184], p < 0.001) and gluteal muscles (−0.322 mmol/L/h [−0.593 to −0.051], p = 0.022) was associated with a reduction in postprandial glycemic response. Collectively, short, frequent walking or squatting breaks effectively enhance glycemic control in overweight and obese men compared to a single bout of walking within prolonged sitting. These superior benefits seem to be associated with increased muscle activity intensity in the targeted muscle groups during frequent transitions from sitting to activity. [ABSTRACT FROM AUTHOR]

Context: Whole-body vibration (WBV) training improves muscle strength and balance. Few studies have focused on the effects of WBV frequencies below 30 Hz. We aimed to investigate the effect of low-frequency WBV training on muscle activity, fatigue recovery, and oxygen consumption (VO2). Design: Prospective single-group, repeated-measures study. Methods: In this controlled laboratory setting study, 20 healthy adults (age 23.26 [1.66] y) performed half squats at 0, 4, 6, 8, 12, 16, 20, 24, and 30-Hz WBV. Muscle activity was evaluated using the root mean square and peak electromyography amplitude of 6 muscles (iliocostalis, rectus abdominis, rectus femoris, biceps femoris, tibialis anterior, and gastrocnemius) obtained via surface electromyography. VO2 was measured during the squats using a gas analyzer, and fatigue recovery was evaluated using measurements of lactate after the squats and after a recovery period. Statistical significance was set at P < .05, and analysis of variance was conducted to determine differences in muscle activity, fatigue, recovery, and VO2, with post hoc analyses as appropriate. Results: Of the 6 muscles measured, the muscle activity of the gastrocnemius alone significantly increased from 0 Hz at 4, 8, 12, 16, 24, and 30 Hz based on the root mean square values and at 4, 8, 12, and 30 Hz based on the peak electromyography amplitude values. There were no significant differences in the other muscles. There were no significant differences in VO2 or in lactate levels. Conclusions: Low-frequency WBV during squat exercises significantly increased the activity of the gastrocnemius medialis only at specific frequencies in healthy young adults. Low-frequency WBV is safe and has the potential to increase muscle activity. [ABSTRACT FROM AUTHOR]

Purpose: Previous research suggests that the percentage of maximal oxygen uptake attained and the time it is sustained close to maximal oxygen uptake (eg, >90%) can serve as a good criterion to judge the effectiveness of a training stimulus. The aim of this study was to investigate the acute effects of adding vibration during varied high-intensity interval training (HIIT) sessions on physiological and neuromuscular responses. Methods: Twelve well-trained cyclists completed a counterbalanced crossover protocol, wherein 2 identical varied HIIT cycling sessions were performed with and without intermittent vibration to the lower-intensity workloads of the work intervals (6 × 5-min work intervals and 2.5-min active recovery). Each 5-minute work interval consisted of 3 blocks of 40 seconds performed at 100% of maximal aerobic power interspersed with 60-second workload performed at a lower power output, equal to the lactate threshold plus 20% of the difference between lactate threshold and maximal aerobic power. Oxygen uptake and electromyographic activity of lower and upper limbs were recorded during all 5-minute work intervals. Results: Adding vibration induced a longer time ≥90% maximal oxygen uptake (11.14 [7.63] vs 8.82 [6.90] min, d = 0.64, P =.048) and an increase in electromyographic activity of lower and upper limbs during the lower-intensity workloads by 20% (16%) and 34% (43%) (d = 1.09 and 0.83; P =.03 and.015), respectively. Conclusion: Adding vibration during a varied HIIT session increases the physiological demand of the cardiovascular and neuromuscular systems, indicating that this approach can be used to optimize the training stimulus of well-trained cyclists. [ABSTRACT FROM AUTHOR]

Objectives: Single denture rehabilitated patients have negative appraisals regarding oral function, mostly associated by stability and retention issues regarding mandibular prosthetics. Therefore, this study assessed patients' occlusal equilibration, muscle activity, and oral health-related quality of life (OHRQoL) receiving milled removable or fixed mandibular implant retained prostheses. Materials and methods: Twenty-two edentulous mandibular ridges patients were randomly distributed into two groups based on the definitive prosthesis received. Group I: Removable mandibular implant-supported overdenture, Group II: Implant retained fixed prosthesis. Occlusal equilibration was evaluated utilizing Occlusense, muscle activity via Electromyograph (EMG) at delivery, after one, and three months. The OHRQoL was evaluated by Oral Health Impact Profile questionnaire (OHIP-19) before delivery and after follow-ups. Data were collected, tabulated, and analyzed, utilizing independent t-test and One-way ANOVA followed Tukey's post-hoc test. Significance level set at P ≤ 0.05. Results: Groups I &II showed significant improvement in occlusal equilibration, muscle activity and OHRQoL. Group II demonstrated significantly higher improvement than group I in occlusal equilibration associated with muscle activity after 1 month, and in functional limitations domain in OHRQoL questionnaire after 3 months. Conclusion: Implant retained mandibular prosthesis showed improvement in occlusal equilibration, muscle activity, and OHRQoL regardless of prosthesis type employed. Fixed implant-supported prosthesis revealed better outcomes than removable mandibular implant-supported overdenture concerning occlusal equilibration, muscle activity, and OHRQoL regarding functional limitations. Clinical relevance: Implant retained mandibular prosthesis is one of best treatment options for single mandibular completely edentulous patients, as dental implants improved occlusal equilibration, muscle activity, and OHRQoL. [ABSTRACT FROM AUTHOR]

Background: Lingual pressure (LP) generation is cooperatively controlled not only by the intrinsic tongue (I‐ton) muscles but also by hyoid muscle activation. However, the measurement of endurance and fatigue properties of I‐ton muscles is difficult due to the instability of electrodes. Objective: The purpose of this study was to apply suction electrodes to measure electromyograms (EMGs) of I‐ton muscle and to evaluate integrated EMG amplitude (iEMG) and mean power frequency (MPF) of EMG in the I‐ton and hyoid muscles performing continuous LP. Methods: Twenty healthy adult volunteers (10 males, 10 females, mean age 28.8 years) were instructed to perform 10‐s LP generation tasks at 25%, 50%, 75% and 100% of maximum LP in randomised order with visual feedback. During each task, EMGs of the I‐ton, suprahyoid (S‐hyo), infrahyoid (I‐hyo) and masseter (Mass) muscles were simultaneously recorded. The iEMG and MPF of EMG burst during 10‐s LP tasks were compared. The recording period was divided into three substages to analyse temporal changes with the Friedman test. Results: During the 10‐s task, the iEMG significantly increased as the LP strength increased (p <.001). There was no time‐dependent change in the I‐ton iEMG; however, the MPF of the I‐ton EMG burst decreased in all tasks (p <.05). The S‐hyo and I‐hyo iEMGs gradually increased, especially with strong LP (p <.01). Conclusion: While I‐ton muscles may easily fatigue during 10‐s LP generation, S‐hyo and I‐hyo muscles may help compensate for the weakened I‐ton muscle activity by increasing their activity to maintain LP. [ABSTRACT FROM AUTHOR]

BACKGROUND: To improve gait disability in patients with chronic stroke, ankle muscle strengthening and calf muscle stretching exercises are required. However, currently available ankle training equipment limit ankle exercises based on the position. Recently developed ankle training equipment enables spring resistance-based plantar press exercises to be performed in the standing position with weight support. OBJECTIVE: To conduct a usability test of the ankle training equipment in the standing position by stroke patients with hemiplegic gait and verify its effects on ankle movements. METHODS: The ankle training equipment was applied to five patients with chronic stroke and hemiplegic gait. In the standing position, the patients performed forefoot and rearfoot press exercises in the affected side with a day's interval at 20 repetitions maximum (RM). During the exercises, surface electromyography (sEMG) was used to measure the maximum voluntary isometric contraction (%MVIC) of the leg muscles. The System Usability Scale (SUS) was used to assess the ankle training equipment. Wilcoxon signed-rank test was used to evaluate the differences in muscle activity between the two exercises. RESULTS: Forefoot and rearfoot press exercises increased the %MVIC in the biceps femoris. Additionally, the tibialis anterior and medial gastrocnemius activity was significantly different between the two exercises. The SUS was 78.75% (SD 12.7). CONCLUSION: The usability test of the passive-control foot press trainer (PFPT) that with improvements in the structure and functions for convenience, it could be commercialized. PFPT could be an alternative to the ankle rehabilitation robot that necessitates a sitting position. [ABSTRACT FROM AUTHOR]

The deep neck flexors are important for maintaining neck posture by stabilizing and supporting it through low-intensity contraction, ensuring static endurance. The subjects performed computer tasks after having their deep neck flexor endurance measured using a pressure biofeedback unit. The craniovertebral angle (CVA) and the muscle activities were measured while participants were completing computer tasks for 10 min. The deep neck flexor endurance was significantly negatively correlated with CVA changes at 0–2 min. The deep neck flexor endurance was significantly negatively correlated with sternocleidomastoid muscle and upper trapezius activity at 0–2 min. The deep neck flexor endurance negatively predicted CVA changes at 0–2 min and explained 28.8% of the variance in the CVA changes. The lower the deep neck flexor endurance, the earlier the simultaneous changes occurred in the CVA and the neck and shoulder muscle activities during computer tasks. [ABSTRACT FROM AUTHOR]

Objective: We aimed to investigate the muscle coordination differences between a control group and patients with mild and severe knee osteoarthritis (KOA) using muscle synergy analysis and determine whether muscle coordination was associated with symptoms of KOA. Method: Fifty-three women with medial KOA and 19 control patients participated in the study. The gait analyses and muscle activity measurements of seven lower limb muscles were assessed using a motion capture system and electromyography. Gait speed and knee adduction moment impulse were calculated. The spatiotemporal components of muscle synergy were extracted using non-negative matrix factorization, and the dynamic motor control index during walking (walk-DMC) was computed. The number of muscle synergy and their spatiotemporal components were compared among the mild KOA, severe KOA, and control groups. Moreover, the association between KOA symptoms with walk-DMC and other gait parameters was evaluated using multi-linear regression analysis. Results: The number of muscle synergies was lower in mild and severe KOA compared with those in the control group. In synergy 1, the weightings of biceps femoris and gluteus medius in severe KOA were higher than that in the control group. In synergy 3, the weightings of higher tibial anterior and lower gastrocnemius lateralis were confirmed in the mild KOA group. Regression analysis showed that the walk-DMC was independently associated with knee-related symptoms of KOA after adjusting for the covariates. Conclusions: Muscle coordination was altered in patients with KOA. The correlation between muscle coordination and KOA may be attributed to the knee-related symptoms. Key points • Patients with knee osteoarthritis (OA) experienced a deterioration in muscle coordination when walking. • Loss of muscle coordination was associated with severe knee-related symptoms in knee OA. • Considering muscle coordination as a knee OA symptom-related factor may provide improved treatment. [ABSTRACT FROM AUTHOR]

Objective: The present study aims to evaluate the effects of posture, task, and handgrip style on discomfort, neck kinematics, and concomitant muscular activity when using a smartphone (SP). Background: Along with the popularity of smartphones, musculoskeletal disorders have become prevalent among smartphone users. However, comprehensive aspects of discomfort, kinematics, and electromyographic responses across various conditions remain to be investigated. Method: Twenty-four young smartphone users performed typing, video watching, and reading tasks while holding the smartphone both with one hand and with two hands while either sitting or standing. Neck kinematics and muscular activities were simultaneously recorded. Results: Working with SPs led to higher discomfort in the neck (p = 0.01), lower back (p = 0.01), and shoulder (p = 0.04) while sitting as compared to standing. Sitting was associated with greater neck flexion and more minor lateral bending for all tasks and grip styles (p < 0.05). Electromyographic analysis indicated significant differences between sitting and standing, with alterations being dependent on the test condition. Moreover, neck kinematics and muscular activities significantly differed based on the task nature, handgrip, and interactions. Conclusion: This study highlights the risk of using smartphones in increased neck angle flexion and muscular activities fatigue. Thus, posture and handgrip should be considered while using SPs. As each test condition affects a specific dependent variable, a holistic approach is required to evaluate the responses of SP users' musculoskeletal systems. Application: Results can be applied to develop guidelines for musculoskeletal disorders/discomfort prevention among SP users, especially with the rise of smartphone use during the COVID-19 pandemic. [ABSTRACT FROM AUTHOR]

Canoe sprint continues to be an area within sports research that is not thoroughly explored, resulting in a limited number of studies that examine muscle activity across varying intensities and the dynamic changes in peak muscle activation over a distance. This study aims to bridge this gap by providing comprehensive insights into muscle engagement among canoe paddlers, with a specific focus on simultaneously assessing 16 muscles. This study is the first in Latvia to use electromyography to analyze canoe paddlers' muscle activity. The study's main objective is to evaluate muscle electromyographic activity and the sequence of achieving peak activity in canoe paddlers at loads of varying intensity. To accomplish the research objectives of examining the electromyographic activity of the brace and the sequence in which muscles reach their peak activity in canoe paddlers at loads of varying intensity and to evaluate differences in electromyographic muscle activity and the sequence of reaching peak muscle activity at loads of varying intensity, a laboratory study was undertaken at the Healthcare in Sport Research Centre of Latvian Academy of Sports Education (LASE). The study involved five adult canoe paddlers who are masters of the sport, possess extensive experience in international competitions, and have been engaged in canoeing for more than six years. The primary methods employed include electromyography (FreeEMG1000 with 16 wireless surface electrode sensors), video analysis (BTS SMART DX infrared cameras), and ergometry (Dansprint canoe ergometer). Significant differences in a brace's average and peak muscle activity at loads of varying intensity were observed. For example, Participant No. 2 exhibited a midtrapezius peak activity of 701 units at the start of the 2-min test, which decreased to 421 units by the end of the test. The muscle activity during paddling was asymmetric, with notable differences between the paddling and opposite sides. For instance, in the 200-m test for Participant No. 4, the average gluteus medius peak muscle activity on the opposite side was 722 units, whereas on the paddling side, it was 199. Additionally, by the conclusion of the 200-m test, Participant No. 5 experienced a rapid decline in gluteus muscle activity, coinciding with a reduction in paddling power. Across all participants, the gluteus medius and gluteus maximus muscles on the opposite side exhibited significantly higher peak activity than those on the paddling side. This finding may explain the observed asymmetry in pelvic musculature among canoe paddlers. [ABSTRACT FROM AUTHOR]

Background: The barbell squat is an exercise used to strengthen the lower limbs, with implications for both performance in sports and improving movement during everyday tasks. Although the exercise is being trained across a variety of repetition ranges, the technical requirements may vary, affecting appropriate repetition range for specific training goals. Methods: A randomised within-subject design was used to compare kinematics and surface electromyography (EMG) in the lower extremities during different concentric phases (pre-, sticking- and post-sticking region) of the last repetition when performing squats at different repetition maximums (RMs). Thirteen strength-trained men (age: 23.6 ± 1.9 years; height: 181.1 ± 6.5 cm; body mass: 82.2 kg, 1RM: 122.8 ± 16.2, relative strength: 1.5 ± 0.2 x body mass in external load) performed a 1, 3, 6, and 10RM squat, in a randomised order. Results: The main findings were that barbell-, ankle-, knee- and hip kinematics were similar across different repetition ranges, except for a smaller trunk lean at 1RM in the pre-sticking region compared to other repetitions and in the sticking region compared to 10RM (p ≤ 0.04). Furthermore, 1RM revealed significantly higher EMG amplitude in the vastus lateralis, gastrocnemius and soleus in the sticking and post-sticking regions when compared to 10RM. It was concluded that 10RM may locally fatigue the vastus lateralis and plantar flexors, explaining the lower EMG amplitude. The observed differences indicate that requirements vary for completing the final repetition of the 10RM compared to the 1RM, an important aspect to consider in training to enhance 1RM strength. [ABSTRACT FROM AUTHOR]

Introduction: Pain is a common health problem among older adults worldwide. Older adults tend to suffer from arm, lumbar, and back pain when using hanging cabinets. Methods: This study used surface electromyography to record muscle activity and a motion capture system to record joint motion to research effects of different loads and retrieval postures on muscle activity and joint range of motion when older adults retrieve objects from a high place, to provide optimised feedback for the design of hanging cabinet furniture. Results: We found that: 1) The activity of BB (Biceps brachii) on the side of the body interacting with the cabinet door was greater than that of UT (Upper trapezius) and BR (Brachial radius) when retrieving objects from a high place, the activity of UT on the side of the body interacting with a heavy object was greater than that of BB and BR. 2) The activity of UT decreases when the shoulder joint angle is greater than 90°, but the activity of BB increases as the angle increases. In contrast, increasing the object's mass causes the maximum load on the shoulder joint. 3) Among the different postures for overhead retrieval, alternating between the right and left hand is preferable for the overhead retrieval task. 4) Age had the most significant effect on overhead retrieval, followed by height (of person), and load changes were significantly different only at the experiment's left elbow joint and the L.BR. 5) Older adults took longer and exerted more effort to complete the task than younger adults, and static exercise in older adults may be more demanding on muscle activity in old age than powered exercise. Conclusion: These results help to optimise the design of hanging cabinet furniture. Regarding the height of hanging cabinets, 180 cm or less is required for regular retrieval movements if the human height is less than 150 cm. Concerning the depth of the hanging cabinets, different heights chose different comfort distances, which translated into the depth of the hanging cabinets; the greater the height, the greater the depth of the hanging cabinets to use. [ABSTRACT FROM AUTHOR]

Exoskeletons, traffic accident, stroke, etc. In this study, a lower extremity exoskeleton made of A Glass Fiber material was designed using Solidworks program. The A Glass Fiber material used in the design has reduced the weight of the exoskeleton up to 9 kg, including the engine weights. The designed exoskeleton was superimposed on the AMMR V.1.6.3 human musculoskeletal full-body model in the AnyBody program, with overlapping joint points, and biomechanical analyzes were performed throughout the gait cycle. As a result of biomechanical analysis, data on muscle activities, muscle strength, joint moment and reaction force were obtained. Data were collected and analyzed on two different walking models, with and without exoskeleton. The simulation results showed that the S geometry of the exoskeleton at the level of the femur and tibia bones is more suitable for the human anatomical structure, and the force transmission from the trunk to the legs is evenly distributed throughout the gait cycle. When the muscle activities and muscle strength data are examined, it is seen that walking with the exoskeleton will increase the anterior-posterior strength of the hip by working the psoas major muscle more. [ABSTRACT FROM AUTHOR]

Trunk muscle activity and thoraco-lumbar kinematics can discriminate between non-specific chronic low back pain (NSCLBP) subgroups and healthy controls. However, research commonly focuses on lumbar kinematics, with limited understanding of relationships between kinematics and muscle activity across clinical subgroups. Similarly, the thoracic spine, whilst intuitively associated with NSCLBP, has received less attention and potential relationships between spinal regions and muscle activity requires exploration. Is there a relationship between trunk muscle activation and regional thoracic and lumbar kinematics in NSCLBP subgroups during a forward bending task? Observational, case-control study. Fifty subgrouped NSCLBP motor control impairment participants (27 Flexion Pattern (FP-MCI), 23 Active Extension Pattern (AEP-MCI)) and 28 pain-free controls were evaluated using 3D motion analysis (Vicon™) and surface electromyography during a forward bending and return to upright task. Mean sagittal angles for the upper-thoracic (UTx), lower-thoracic (LTx), upper-lumbar (ULx) and lower-lumbar (LLx) regions were compared with normalised (% sub-maximal voluntary contraction) mean amplitude electromyography of bilateral transversus abdominis/internal oblique, external oblique, superficial lumbar multifidus and erector spinae (longissimus thoracis) muscles between groups. Pearson correlations were computed to assess relationships (significance p < 0.01). AEP-MCI individuals demonstrated statistically significant relationships between superficial lumbar multifidus and ULx and LLx kinematics (−.812 to.659). FP-MCI individuals exhibited statistically significant relationships between erector spinae and superficial lumbar multifidus and LLx and LTx kinematics (−.686 to.664) in both task phases, and between external oblique and LTx during forward bending) (−.459 to.572). Correlations were moderate to strong for all significant relationships (−.812 to.664). Relationships between muscle activity and regional spinal kinematics varied between NSCLBP subgroups, suggesting that those with flexion- or extension-related LBP adopt different motor control strategies when performing a bending task. As effectively mechanical biomarkers, these findings may inform treatment by improving understanding of varied motor strategies in subgroups. • Relationships between muscle activity and spinal kinematics vary in LBP subgroups. • Varied compensatory spinal behaviours indicate that regional insights are important. • As potential biomarkers, this could help personalise rehabilitation approaches. [ABSTRACT FROM AUTHOR]

Purpose: This study investigated the acute effects of a static balance exercise combined with different blood flow restriction (BFR) pressures on motor performance fatigue development and recovery as well as physiological and perceptual responses during exercise in males and females. Methods: Twenty-four recreational active males (n = 13) and females (n = 11) performed static balance exercise on a BOSU ball (3 sets of 60 s with 30 s rest in-between) on three separate (> 3 days) laboratory visits with three different BFR pressures (80% arterial occlusion pressure [AOP], 40%AOP, 30 mmHg [SHAM]) in random order. During exercise, activity of various leg muscles, vastus lateralis muscle oxygenation, and ratings of effort and pain perception were recorded. Maximal squat jump height was measured before, immediately after, 1, 2, 4, and 8 min after exercise to quantify motor performance fatigue development and recovery. Results: Quadriceps muscle activity as well as ratings of effort and pain were highest, while muscle oxygenation was lowest in the 80%AOP compared to the 40%AOP and SHAM condition, with no differences in postural sway between conditions. Squat jump height declined after exercise with the highest reduction in the 80%AOP (− 16.4 ± 5.2%) followed by the 40%AOP (− 9.1 ± 3.2%), and SHAM condition (− 5.4 ± 3.3%). Motor performance fatigue was not different after 1 min and 2 min of recovery in 40% AOP and 80% AOP compared to SHAM, respectively. Conclusion: Static balance exercise combined with a high BFR pressure induced the largest changes in physiological and perceptual responses, without affecting balance performance. Although motor performance fatigue was increased by BFR, it may not lead to long-term impairments in maximal performance. [ABSTRACT FROM AUTHOR]

In tennis athletes with scapular dyskinesis, the activation of the scapulothoracic muscles during serve is not known. Also, the mechanical properties (tone, elasticity, and stiffness) of the scapulothoracic muscles of the tennis athletes with scapular dyskinesis are likely to change. The study aimed to evaluate the activation of the scapulothoracic muscles while performing tennis serve and to determine the changes in the mechanical properties of the same muscles in young tennis athletes with scapular dyskinesis. Seventeen tennis athletes with scapular dyskinesis aged between 11 and 18 years (the scapular dyskinesis group) and age- and gender-matched 17 asymptomatic tennis athletes (the control group) were included in the study. Activation of scapulothoracic muscles (descending-transverse-ascending trapezius and serratus anterior) in the 3 phases (preparation, acceleration, and follow-through) of the serve was evaluated using surface electromyography, and the mechanical properties of the same muscles were measured at rest by myotonometry. Ascending trapezius activation in the follow-through phase was lower in the scapular dyskinesis group compared with the control group (mean difference 95% confidence interval: −22.8 [−41.2 to −4.5]) (P =.017). The tone and stiffness of the transverse trapezius (P =.043 and P =.017, respectively) were higher, whereas the same parameters of the ascending trapezius were lower (P =.008 and P =.010, respectively) in the scapular dyskinesis group compared with the control group. Activation of the ascending trapezius and the tone and stiffness of the transverse-ascending trapezius were altered in tennis athletes with scapular dyskinesis. Implementations to improve these changes can be included in the rehabilitation or training programs of young tennis athletes with scapular dyskinesis. [ABSTRACT FROM AUTHOR]

Generating large mechanical power during actions such as sprinting or jumping is a crucial factor in many sports. These types of actions require a good warm-up activation. Capacitive-Resistive Electric Transfer (CRET) is a non-invasive therapy based on the application of radio frequency electric currents within the range of 300 kHz–1.2 MHz to accelerate tissue metabolic activity. This study aimed to evaluate the effectiveness of adding CRET to an active warm-up protocol in young adult athletes. For the double-blind randomized clinical trial, 60 healthy athletes were recruited and divided into an Experimental group (EG) and a Sham group (SG). EG received a CRET protocol in addition to an active warm-up. SG carried out the same warm-up but with a placebo CRET. The main outcome measures were isometric extension force, countermovement-jump (CMJ), 30 m-sprint test, and surface electromyography (sEMG). There is no statistically significant interaction (group–time) for any of the variables studied. Significant main effects for time were found in isometric extension force (p = 0.008); 30 m sprint (p = 0.017); rectus femoris sEMG during CMJ (p = 0.002); vastus lateralis sEMG during CMJ (p = 0.012); vastus medialis during CMJ (p = 0.010) and rectus femoris sEMG during the 30 m sprint test (p = 0.012). Non-significant differences between means are observed in the isometric extension force (48.91 EG; 10.87 SG) and 30 m sprint (−0.13 EG; −0.04 SG) variables. To conclude, a non-significant tendency was observed in sprint and quadriceps strength following CRET therapy, compared to the individuals' pre-treatment state. Future research should use more treatment sessions to observe this tendency. [ABSTRACT FROM AUTHOR]

Background and Aims Abnormal posture and alterations in movement and muscle activity patterns have been reported in people with upper cross syndrome (UCS). These changes can lead to imbalance in muscle activation, altered movement patterns, and biomechanical changes. The present study aims to investigate the effect of corrective exercises on posture, upper extremity muscle activity, and shoulder kinematics in male handball players with UCS. Methods This quasi-experimental study was conducted on 30 male handball players with UCS who were randomly divided into exercise (n=15) and control (n=15) groups. The variables including upper extremity muscle activation patterns, shoulder kinematics, forward head posture, forward shoulder posture, and kyphosis were evaluated before and after intervention. Should kinematics and activation patterns of upper extremity muscles (supraspinatus, lumbar erector spinae, upper trapezius, middle trapezius, latissimus dorsi, pectoralis major) were recorded using electromyography and motion analyzer. The angles of forward head and forward shoulder were assessed using photographic method taken from lateral view, and Kyphosis angle was measured using a flexible ruler before and after exercises. The exercise group performed the comprehensive corrective exercises for 8 weeks (3 sessions per week), but the control group did not receive any intervention. To analyze the data, two-way analysis of variance and Bonferroni test were used. The significant level was set at 0.05. Results Forward head posture (P=0.001), forward shoulder posture (P=0.003), and kyphosis (P=0.002) showed significant improvements in the exercise group compared to the control group from pretest to post-test phase. In the preparatory and throw phases (slow and fast throwing), higher activities of supraspinatus, lumbar erector spinae, upper trapezius, middle trapezius, latissimus dorsi, and pectoralis major were observed in the exercise group compared to the control group (P=0.05). Moreover, in the preparatory and throw phases, higher range of motion of shoulder flexion, forward flexion of shoulder, internal rotation of shoulder, external rotation of shoulder, and shoulder abduction were observed in the exercise group compared to the control group (P=0.05). Conclusion Corrective exercises can significantly alter shoulder kinematics and upper extremity muscle activity patterns in male handball players with UCS, which can be used in future studies to prevent UCS in handball players during throwing the ball. [ABSTRACT FROM AUTHOR]

IntroductionTasks performed at or above head height in industrial workplaces pose a significant challenge due to their association with musculoskeletal disorders. Upper-body exoskeletons have been identified as a potential solution for mitigating musculoskeletal loads and fighting against excessive muscular fatigue. However, the influence of such support on fine motor control, as well as on cognitive-motor interference, has received limited attention thus far. Therefore, this crossover randomized study aimed to investigate the impact of the use of a passive upper-body exoskeleton in the presence of muscular fatigue or not. Additionally, focusing on differences between single (ST) and dual (DT) industrial tasks consisting of overhead speed and accuracy exercises.MethodsIn both scenarios, N = 10 participants (5 male/5 female) engaged in an overhead precision task using a nail gun to precisely target specific areas on three differently sized regions, based on Fitts’ law paradigm (speed-accuracy trade-off task). This was done with and without the passive upper-body exoskeleton, before and immediately after a fatiguing exercise of shoulder and leg muscles. In addition, a second task (dual-task, DT) was carried out in which the occurrence of an auditory signal had to be counted. The main outcomes were muscular activation of the shoulder girdle as well as the time to perform speed-accuracy tasks of different difficulty indexes (calculated by means of Fitts’ law).Results and discussionIn the absence of fatigue, the exoskeleton did not affect the speed-accuracy trade-off management of participants in the single task, but it did in the dual-task conditions. However, after muscle fatigue, the speed-accuracy trade-off was differently affected when comparing its execution with or without the exoskeleton. In general, the dual task resulted in longer times to perform the different tasks, whether it was with or without the exoskeleton. Furthermore, the use of the exoskeleton decreased muscle activity, which is associated with less physical effort, but only significantly for the M. deltoideus and M. trapezius when compared by tasks. Overall, these study findings highlight the potential supportive effects of using an upper-body exoskeleton for industrial overhead tasks.

Treadmill running is a common method of exercise and to study human locomotion. Research has examined the kinematics and kinetics of overground and treadmill running, but there has been less focus on the levels of muscle activity during treadmill running. We investigated if muscle activity is different while running overground compared to running on a variety of treadmills. A total of 11 healthy individuals ran at 3 speeds (2.6, 3.6, 4.5 m/s) under 4 different running conditions (3 treadmills, overground). The three treadmills included a typical home exercise treadmill, a midsize commercial research treadmill, and a large, instrumented research treadmill. Surface EMG of the tibialis anterior (TA), gastrocnemius medialis (GM), rectus femoris (RF) and biceps femoris (BF) muscles were measured for each running condition. The integrated EMG was computed for each running condition for the stance and swing phase, as well as 100 ms before and after the heel-strike. Friedman analysis revealed significant effects during the stance phase for GM and RF at all speeds, such that muscle activation was lower on the treadmills relative to overground. During the stance phase at faster speeds, the muscle activity was higher for the TA and lower for the BF while running on the different treadmills compared to overground running. Before heel-strike, the TA was significantly less active during treadmill compared to overground running at 2.6 m/s and the RF showed significantly higher activity at 3.6 m/s and 4.5 m/s while running on the different treadmills. Summarizing, differences were mainly observed between the different treadmill conditions relative to overground running. Muscle activation differences between the different treadmill conditions were observed at faster running speeds for RF during the pre-heel-strike phase only. Different types of treadmills with different mechanical properties affects the muscle activity during stance phase as well as in preparation to heel-strike. Additionally, the muscle activity is greater during overground compared to treadmill running during the stance phase for the GM, BF, and RF.

Introduction: Dental occlusion contributes to the development of temporomandibular disorder. Objective: This case control study examined the influence of different occlusal conditions on the surface electromyography (sEMG) of the superficial part of the masseter muscle (MM) and anterior part of the temporalis muscle (TA) during clenching in the maximum intercuspal position (MIP). Materials and methods: Twelve healthy subjects had their anterior, right posterior, or left posterior teeth added by composite resin to generate the bilateral posterior, unilateral left, or unilateral right posterior tooth losses, respectively. Muscle activity in the resting stage, MM’s and TA’s maximum voluntary clenching (MVC; µV) in MIP, each muscle activity’s symmetry (%), and ipsilateral MM and TA synergy (%) were measured by sEMG. All parameters were analyzed by SPSS version 23.0, and the significance level was set at p

Background: A torn rotator cuff muscle deteriorates over time leading with an increase in muscle atrophy and fatty infiltration. There are several clinical assessments for evaluating the atrophy of the torn supraspinatus muscle. However, it is unclear which approach can more accurately estimate the activity of the torn supraspinatus muscle. The purpose of this study was to determine which magnetic resonance imaging–based muscle atrophy imaging assessment currently implemented in the clinical setting accurately estimates the activity of the torn supraspinatus muscle. Methods: Forty patients who were diagnosed with a rotator cuff tear and were candidates for repairs were selected for this study. Cross-sectional area, occupation ratio, and tangent sign were analyzed on T1-weighted oblique sagittal plane magnetic resonance images in which the scapular spine leads to the Y-section. Muscle belly ratio of the supraspinatus muscle was analyzed by calculating the ratio of the width of the muscle belly to the distance from the greater tubercle to the proximal end of the muscle on T1-weighted coronal plane magnetic resonance imaging images. Fatty infiltration was evaluated using the Goutallier classification system. Tear size was obtained intraoperatively by measuring the width and length of the tear and classified based on the Cofield’s classification. To assess activity of the torn supraspinatus muscle, participants were first instructed to sit on a chair with the affected arm resting on a table and the shoulder abducted to 60° in the scapular plane with neutral rotation. Elasticity of the supraspinatus muscle belly was then obtained at rest and during isometric contraction using with real-time tissue elastography. Muscle activity, a surrogate for contractility, was defined as the difference between the elasticities measured at rest and during isometric contraction. A stepwise multiple regression analysis was used to investigate independent factors, such as sex, tear width, cross-sectional area, occupation ratio, tangent sign, and muscle belly ratio, related to muscle activity. Results: Stepwise multiple regression analysis (R2 = 0.522, P

Previous studies examining the flexion–relaxation phenomenon (FRP) in back muscles through trunk forward flexion tests have yielded inconsistent findings, primarily due to variations in leg posture control. This study aimed to explore the influence of leg posture control and individual flexibility on FRP in back and low limb muscles. Thirty-two male participants, evenly distributed into high- and low-flexibility groups, were recruited. Activities of the erector spinae, biceps femoris, and gastrocnemius muscles, alongside the lumbosacral angle (LSA), were recorded as participants executed trunk flexion from 0° to 90° in 15° increments, enabling an analysis of FRP and its correlation with the investigated variables. The findings highlighted significant effects of all examined factors on the measured responses. At a trunk flexion angle of 60°, the influence of leg posture and flexibility on erector spinae activities was particularly pronounced. Participants with limited flexibility exhibited the most prominent FRP under constrained leg posture, while those with greater flexibility and unconstrained leg posture displayed the least FRP, indicated by their relatively larger LSAs. Under constrained leg posture conditions, participants experienced an approximate 1/3 to 1/2 increase in gastrocnemius activity throughout trunk flexion from 30° to 90°, while biceps femoris activity remained relatively constant. Using an inappropriate leg posture during back muscle FRP assessments can overestimate FRP. These findings offer guidance for designing future FRP research protocols.

Background: Incisional hernia is a common complication following abdominal surgery. It causes change in function of core abdominal muscles leading to change in abdominal wall dynamics. This study aims to objectively measure and compare preoperative abdominal wall dynamics with surface electromyography (sEMG) in incisional hernia patients with healthy individuals. Materials and methods: In this prospective comparative study, two groups of participants as cases and controls were evaluated for their abdominal wall dynamics by using sEMG. Both cases and controls were evenly matched in terms of age and gender. Statistical analysis was done with STATA 14.1 and p value of < 0.05 was considered significant. Results: Demographic profile was comparable between the two groups. Mean BMI of cases was higher than controls. The most common index procedure was lower segment cesarean section. The strength and power of all three abdominal wall muscles (rectus abdominis, external oblique, internal oblique) were significantly diminished among cases compared to controls. Conclusions: Abdominal wall dynamics can be objectively and correctly interpreted from sEMG of abdominal wall core muscles in patients with incisional hernia. This study shows that there is a decrease in abdominal wall strength and power in patients suffering from incisional hernia in comparison with healthy controls. [ABSTRACT FROM AUTHOR]

Dental occlusion contributes to the development of temporomandibular disorder. This case control study examined the influence of different occlusal conditions on the surface electromyography (sEMG) of the superficial part of the masseter muscle (MM) and anterior part of the temporalis muscle (TA) during clenching in the maximum intercuspal position (MIP). Twelve healthy subjects had their anterior, right posterior, or left posterior teeth added by composite resin to generate the bilateral posterior, unilateral left, or unilateral right posterior tooth losses, respectively. Muscle activity in the resting stage, MM's and TA's maximum voluntary clenching (MVC; µV) in MIP, each muscle activity's symmetry (%), and ipsilateral MM and TA synergy (%) were measured by sEMG. All parameters were analyzed by SPSS version 23.0, and the significance level was set at p < 0.05. The MM's and TA's sEMG activity at the resting stage significantly differed from those at the other occlusal conditions (p < 0.05). Both muscles' MVC were highest at the MIP during clenching but lowest during anterior clenching. During unilateral posterior clenching, such MVC was higher at the occluding than at the non-occluding sides. The TA's symmetry during clenching at the anterior and unilateral posterior teeth was lower than that at the MIP during clenching. No significant difference was seen in the ipsilateral MM and TA synergy. Different occlusal conditions influenced the MM's and TA's sEMG activity. Each masticatory muscle responded differently to the same occlusal conditions. [ABSTRACT FROM AUTHOR]