Body Muscle Activity Research Articles

Changing the Mandibular Position in Rowing: A Brief Report of a World-Class Rower.

We investigated the acute biophysical responses of changing the mandibular position during a rowing incremental protocol. A World-class 37-year-old male rower performed two 7 × 3 min ergometer rowing trials, once with no intraoral splint (control) and the other with a mandibular forward repositioning splint (splint condition). Ventilatory, kinematics and body electromyography were evaluated and compared between trials (paired samples t-test, p ≤ 0.05). Under the splint condition, oxygen uptake was lower, particularly at higher exercise intensities (67.3 ± 2.3 vs. 70.9 ± 1.5 mL·kg-1·min-1), and ventilation increased during specific rowing protocol steps (1st-4th and 6th). Wearing the splint condition led to changes in rowing technique, including a slower rowing frequency ([18-30] vs. [19-32] cycles·min-1) and a longer propulsive movement ([1.58-1.52] vs. [1.56-1.50] m) than the control condition. The splint condition also had a faster propulsive phase and a prolonged recovery period than the control condition. The splint reduced peak and mean upper body muscle activation, contrasting with an increase in lower body muscle activity, and generated an energetic benefit by reducing exercise cost and increasing rowing economy compared to the control condition. Changing the mandibular position benefited a World-class rower, supporting the potential of wearing an intraoral splint in high-level sports, particularly in rowing.

10. COMPARISON OF ERGONOMICS BETWEEN ROBOTIC AND CONVENTIONAL SURGERY: A STUDY OF MUSCLE ACTIVITY AND BODY POSTURE

Abstract Introduction The objective of this study is to compare the ergonomics of surgeons during surgical procedures using the Versius robot (CMR Surgical) and conventional laparoscopic surgery. The study assesses surgeons' body posture and muscle activity to objectively identify ergonomic distinctions between the two surgical approaches. Methods A set of surgeons were asked to perform both tasks in a box trainer and surgical procedures in an experimental model. Laparoscopic tasks and procedures were performed both with the robotic platform and conventionally. During the study, surgeons wore electromyography sensors to measure the activity of 14 muscles. Participants also wore inertial sensors to record body movements. Postures were compared with ergonomic guidelines for conventional and robotic laparoscopic surgery. Results In terms of muscle activity in box trainer and in vivo surgeries, the activity distribution of the gastrocnemius, vastus lateralis, erector spinae and medial trapezius muscles was concentrated around a lower median in robotic procedures compared to conventional ones. However, for the brachioradialis, triceps and upper trapezius, the distribution was concentrated at a higher median for robotic procedures. Regarding surgeon posture, a more ergonomically suitable posture is obtained for flexion-extension of the knee and ulnar-radial deviation of the wrist during robotic surgery. Conclusion The study concludes that the use of robotic surgery improves certain aspects of ergonomics in laparoscopy.

Relevant Biomechanical Variables in Skateboarding: A Literature Review.

Skateboarding, once regarded primarily as a means of transportation and entertainment for youth, has become a recognized professional sport, gaining global popularity. With its recent inclusion in the Olympics, a growing imperative exists to comprehensively understand biomechanics explaining skateboarding performance. This literature review seeks to consolidate knowledge within this domain, focusing on experimental and modeling studies about skateboard riding and tricks. The criteria for study selection encompassed content relevance and publication year, spanning from the last two decades and extending further back to 1980 following cross-referencing of seminal works. Peer-reviewed journal articles, conference proceedings, and books were considered, with comprehensive searches conducted on electronic databases, including SCOPUS, PubMed, Scielo, and Taylor & Francis. Comprehending the biomechanical facets of skateboarding is essential in promoting its use and ensuring safety among all practitioners. Insights into factors such as body kinetics, kinematics, and muscle activation represent a foundational step toward understanding the nuances of this sport with implications for both clinical and biomechanical research. Modern data collection systems such as inertial measurement units (IMU) and electromyography (EMG) offer unprecedented insights into human performance during skateboarding, such as joint range of motion, coordination, and muscle activation, whether in casual riding or executing complex tricks and maneuvers. Developing robust modeling approaches also holds promise for enhancing skateboarding training and performance. Crucially, these models can serve as the initial framework for understanding injury mechanisms and implementing strategies to improve performance and mitigate injury risks.

Effects of a Posture Correction Feedback System on Upper Body Posture, Muscle Activity, and Fatigue During Computer Typing

Effects of a Posture Correction Feedback System on Upper Body Posture, Muscle Activity, and Fatigue During Computer Typing

Iron Deficiency Anaemia in Women & Its Homoeopathic Management

Anaemia is an important public health concern and is a burning problem faced mainly by women from childhood to menopausal age, affecting almost 25% of the global population. In India, more than 50% of the children, non-pregnant and pregnant women being affected by this condition. Amongst anaemia, Iron deficiency is the most common micronutrient deficiency worldwide. Iron is necessary for various functioning of body including formation of haemoglobin, brain development and regulation of body temperature, muscle activity, and catecholamine metabolism. Lack of iron directly affects the immune system; it diminishes the number of T-cells and the production of antibodies. Besides haemoglobin, iron is a component of myoglobin, the cytochromes, catalase and certain enzyme systems. Iron is essential for binding oxygen to the blood cells. The central function of iron is "oxygen transport", and cell respiration. Keywords: India, Iron Deficiency Anaemia, haemoglobin, erythrocytes, anaemia, PBF- peripheral blood smear.

탄력밴드를 이용한 고유수용성신경근촉진법의 안정화 운동이 몸통 및 엉덩부위 근 활성도에 미치는 영향

This study attempted to investigate body and hip muscle activities, using resistance band against 12 adult men. For this, one leg-supported pose in bridge position, skater-patterned bridge pose, bird-dog exercise in quadruped position and skater-patterned exercise pose trainings were performed. Specifically, the maximum voluntary isometric contraction (MVIC) of internal abdominal oblique, external abdominal oblique, multifidus, gluteus maximus and gluteus medius muscle was measured, using surface electromyography (sEMG) after conducting bridge pose and quadrupled exercise, and the results found the followings: In the bridge exercise and quadrupled exercise intervention-based proprioceptive neuromuscular facilitation (PNF), internal abdominal oblique and external abdominal oblique revealed a significant difference in muscle activity (p<0.05). In multifidus, gluteus maximus and gluteus medius muscle, on the contrary, no significant difference was observed in bridge exercise (p>0.05). In the quadrupled exercise intervention-based PNF, however, a significant difference of muscle activity was found (p<0.05). The above results confirm that a skater pattern which combined the single pattern of the PNF could reduce pain and enhance body stabilization through body balancing if selectively applied to those who are suffering from lumbar pain and difficulty in supporting their body weight due to weak abdominal and hip muscles and anterior pelvic tilt.

Nonlinear neural control using feedback linearization explains task goals of central nervous system for trunk stability in sitting posture

Objective. Characterizing the task goals of the neural control system for achieving seated stability has been a fundamental challenge in human motor control research. This study aimed to experimentally identify the task goals of the neural control system for seated stability. Approach. Ten able-bodied young individuals participated in our experiments, which allowed us to measure their body motion and muscle activity during perturbed sitting. We used a nonlinear neuromechanical model of the seated human, along with a full-state feedback linearization approach and optimal control theory for identifying the neural control system and characterizing its task goals. Main results. We demonstrated that the neural feedback for trunk stability during seated posture uses angular position, velocity, acceleration, and jerk in a linearized space. The mean squared error between the predicted and measured motor commands was less than 0.6% among all trials and participants, with a median correlation coefficient of more than 0.9. Our identified optimal neural control primarily used trunk angular acceleration and near-minimum muscle activation to achieve seated stability while keeping the deviations of the trunk angular position and acceleration sufficiently small. Significance. Our proposed approach to neural control system identification relied on a performance criterion (e.g. cost function) explaining what the functional goal is and subsequently, finds the control law that leads to the best performance. Therefore, instead of assuming what control schemes the neural control might utilize (e.g. proportional-integral-derivative control), optimal control allows the motor task and the neuromechanical model to dictate a control law that best describes the physiological process. This approach allows for a mechanistic understanding of the neuromuscular mechanisms involved in seated stability and for inferring the task goals used by the neural control system to achieve the targeted motor behavior. Such neural control characterization can contribute to the development of objective balance evaluation tools and of bio-inspired assistive neuromodulation technologies.

The effects of an ergonomic chinrest among professional violin players. A biomechanical investigation in a randomised crossover design

This study aimed to compare violinists' upper body kinematics and muscle activity while playing with different supportive equipment: their usual chinrest (UC) or an ergonomic chinrest (EC), each mounted on the violin. Three-dimensional motion capture and electromyographic data were acquired from the upper body while 38 pain-free professional violinists performed an excerpt of a music piece. There were only minor differences between the two set-ups tested. The EC resulted in less left rotation of the head (3.3°), slightly more neck extension (1.3°) and less muscle activity (0.5–1.0 %MVE). However, the overall high static muscle activity (4–10 %MVE across all muscles) was maintained using EC. For both setups, the head posture was left-rotated >15°, ≤6° flexed and left-bent 90% of the time. The EC did not produce a substantial difference in biomechanical load. Instead, future studies may focus on aspects other than chinrest design to lower the static workload demands.

Motion Analysis of Balance Pre and Post Sensorimotor Exercises to Enhance Elderly Mobility: A Case Study.

Quantitative assessment of movement using motion capture provides insights on mobility which are not evident from clinical evaluation. Here, in older individuals that were healthy or had suffered a stroke, we aimed to investigate their balance in terms of changes in body kinematics and muscle activity. Our research question involved determining the effects on post- compared to pre-sensorimotor training exercises on maintaining or improving balance. Our research hypothesis was that training would improve the gait and balance by increasing joint angles and extensor muscle activities in lower extremities and spatiotemporal measures of stroke and elderly people. This manuscript describes a motion capture-based evaluation protocol to assess joint angles and spatiotemporal parameters (cadence, step length and walking speed), as well as major extensor and flexor muscle activities. We also conducted a case study on a healthy older participant (male, age, 65) and an older participant with chronic stroke (female, age, 55). Both participants performed a walking task along a path with a rectangular shape which included tandem walking forward, right side stepping, tandem walking backward, left side stepping to the starting location. For the stroke participant, the training improved the task completion time by 19 s. Her impaired left leg had improved step length (by 0.197 m) and cadence (by 10 steps/min) when walking forward, and cadence (by 12 steps/min) when walking backward. The non-impaired right leg improved cadence when walking forward (by 15 steps/min) and backward (by 27 steps/min). The joint range of motion (ROM) did not change in most cases. However, the ROM of the hip joint increased significantly by 5.8 degrees (p = 0.019) on the left leg side whereas the ROMs of hip joint and knee joint increased significantly by 4.1 degrees (p = 0.046) and 8.1 degrees (p = 0.007) on the right leg side during backward walking. For the healthy participant, the significant changes were only found in his right knee joint ROM having increased by 4.2 degrees (p = 0.031) and in his left ankle joint ROM having increased by 5.5 degrees (p = 0.006) during the left side stepping.

Behaviour and muscle activity across the aquatic-terrestrial transition in Polypterus senegalus.

Amphibious fishes moving from water to land experience continuous changes in environmental forces. How these subtle changes impact behavioural transitions cannot be resolved by comparisons of aquatic and terrestrial locomotion. For example, aquatic and terrestrial locomotion appear distinct in the actinopterygian fish Polypterus senegalus; however, it is unclear how gradual water level changes influence the transition between these locomotor behaviours. We tested the hypothesis in P. senegalus that swimming and walking are part of an incremental continuum of behaviour and muscle activity across the environmental transition from water to land rather than two discrete behaviours, as proposed by previous literature. We exposed P. senegalus to discrete environments from fully aquatic to fully terrestrial while recording body and pectoral fin kinematics and muscle activity. Anterior axial red muscle effort increases as water depth decreases; however, a typical swimming-like anterior-to-posterior wave of axial red muscle activity is always present, even during terrestrial locomotion, indicating gradual motor control changes. Thus, walking appears to be based on swimming-like axial muscle activity whereas kinematic differences between swimming and walking appear to be due to mechanical constraints. A discrete change in left-right pectoral fin coordination from in-phase to out-of-phase at 0.7 body depths relies on adductor muscle activity with a similar duty factor and adductor muscle effort that increases gradually as water depth decreases. Thus, despite distinct changes in kinematic timing, neuromuscular patterning is similar across the water depth continuum. As the observed, gradual increases in axial muscle effort reflect muscle activity changes between aquatic and terrestrial environments observed in other elongate fishes, a modified, swimming-like axial muscle activity pattern for terrestrial locomotion may be common among elongate amphibious fishes.

The Effects of 8-week Online Yoga Training on Body Composition, Muscle Activity, Flexibility, and Balance

PURPOSE The purpose of this study was to investigate the effects of an 8-week online yoga training on body composition, muscle activity, flexibility, and balance in males (n=7) and females (n=15). METHODS Twenty-two participants were recruited and divided into two groups (Exercise group, n=11 and control group, n=11). All participants had two visits. During the visits, body composition, muscle activity for forward and back-bending poses, flexibility for sitting-forward and back-bending poses, and balance for one-leg standing were determined. After 8-week yoga training, all measurements were re-performed. An independent t-test was performed to determine the difference between the exercise and control groups. A two-way repeated measures of ANOVA was used to assess the interaction effects (group*time). All values were represented as mean ± standard deviation. An α level was set at 0.05 for all analyses. RESULTS First, the height significantly increased (F=16.573, &lt;i&gt;p&lt;/i&gt;=0.001) and body fat mass (F=7.109, &lt;i&gt;p&lt;/i&gt;=0.015) and body fat percent (F=7.667, &lt;i&gt;p&lt;/i&gt;=0.012) were significantly decreased after the 8-week online yoga training. Second, the muscle activity for vatus lateralis doing a back-bending pose (F=6.140, &lt;i&gt;p&lt;/i&gt;=0.022) significantly increased after the 8-week online yoga training. Third, the flexibility on sitting-forward bending pose (F=4.661, &lt;i&gt;p&lt;/i&gt;=0.043) and back-bending pose (F=11.650, &lt;i&gt;p&lt;/i&gt;=0.003) were statistically increased after the 8-week online yoga training. Lastly, balance on the Center Of Pressure (COP) X (F=5.769, &lt;i&gt;p&lt;/i&gt;=0.026) and the Center Of Pressure (COP) Y (F=4.365, &lt;i&gt;p&lt;/i&gt;=0.05) significantly increased after the 8-week online yoga training.CONCLUSIONS This study will provide scientific evidence on improving exercise programs using online yoga training on physical activity.

Research On Diagnostic Criteria Of Upper Crossed Syndrome Based On WOS And CNKI Literature

The incidence of upper crossed syndrome (UCS) has become younger, but now, the diagnosis and screening criteria of UCS are different, and researchers can not quickly and intuitively understand the research trend. PURPOSE: Analyze and sort out the research on UCS in Chinese and English databases, and sort out the current diagnostic screening criteria of UCS research, so as to provide some reference for researchers related to UCS in the future. METHODS: All relevant literature on UCS published in CNKI and WOS databases were searched and analyzed by the literature method. RESULTS: WOS research is mainly screened by observing three factors related to UCS, including body angle, muscle activation and movement mode. The scapula is the cornerstone of UCS evaluation, so the scapula dyskinesia test will be conducted. Meanwhile, it will also be measured by photogrammetry and the forward head (≥ 44°), round shoulder (≥ 49°) or thoracic kyphosis (≥ 42°); Some researchers only set the criteria as rake angle, round shoulder angle and kyphosis, and some set the inclusion criteria of Craniovertebral angle as greater than 46°. Haifah considered that skull angle and shoulder angle met one or both of the inclusion criteria of UCS. Moreover, there are also criteria for selecting the deviation of cervical spine line from the centre greater than 2.5 cm based on GPS test, or the horizontal distance from the centre of the external auditory canal to acromioclavicular joint greater than 1 cm. CNKI's clinical diagnostic criteria for UCS mainly start from the three aspects of shoulder and neck pain, head forward and round shoulder. It also includes the situation of pterygoid scapula but almost does not directly include the relevant angles of neck and shoulder as the diagnostic criteria, but as the observation index before and after an intervention. In short, the diagnostic criteria of CNKI's research are more functional symptoms, combined with the history of chronic strain, pain signs, cervical spine imaging data, etc. CONCLUSION: The diagnostic criteria of CNKI are pain and functional symptoms, and WOS focuses on the measurement angle. Supported by Education Science Project of "14th Five-year Plan" of Henan Province Grant ROI 2021YB0031, and Science and Technology Development Project of Kaifeng Grant ROI 2104006.

Upper Body Muscle Activation And Measures Of Sprint Performance

PURPOSE: Effective arm swing and core muscle activation are involved in acceleration and maximal sprinting, yet muscle activity in these areas have not been measured via electromyography (EMG) during over ground sprinting trials. The purpose of this study was to explore the relationship between muscle activation of the upper body and measures of performance during sprint acceleration and maximal sprinting. METHODS: Sixteen participants (20.93 ± 0.96 yrs.; 1.71 ± 0.07 m; 67.69 ± 11.81 kg) completed six 40-m sprint trials on an outdoor track, with three from a block start and three from a split start. Muscle activation was measured via EMG in the triceps brachii, biceps brachii, upper trapezius, anterior deltoid, latissimus dorsi, erector spinae, rectus abdominis, and oblique muscles, recorded as a percentage of maximal voluntary isometric contraction. Split times recorded during each sprint were used to calculate acceleration, net horizontal force (Fh), and the ratio of Fh and resultant ground reaction force (%RF) using previously validated methods. Repeated measures multilevel modeling was used to evaluate the relationship between mean upper body muscle activation and average acceleration, Fh, and %RF during each 10-m window of the sprint. RESULTS: During the 0-10 m window, mean activation of the upper trapezius showed a significant positive relationship with acceleration (t = 2.66, p = 0.01), Fh (t = 2.20, p = 0.03), and %RF (t = 2.57, p = 0.01), erector spinae activation was positively associated with %RF (t = 2.42, p = 0.02), and biceps activation was negatively associated with Fh (t = -2.23, p = 0.03). In the 30-40 m window, there was a significant negative relationship between mean latissimus dorsi activation and %RF (t = -2.16, p = 0.04). There were no significant relationships between upper body muscle activation and indicators of sprint performance detected during the 10-20 m or 20-30 m windows. CONCLUSIONS: These results indicate that upper trapezius muscle activity is important during initial sprint acceleration, which agrees with past research on scapular restriction limiting maximal acceleration while sprinting. After the initial period of sprint acceleration, there was no evidence that greater activation of certain upper body muscles was related to improving maximal sprinting performance.

Comparison between wrap around screens and a head mounted display on driver muscle and kinematic responses to a pedestrian hazard

As driving performance relies heavily on the interpretation of visual information, driving simulators require a visual display that can effectively communicate the virtual environment to the driver. Most high-fidelity visual displays include an expensive system of high-definition projectors and wraparound screens. To reduce the overall cost of a driving simulator while preserving the generalizability of results to naturalistic driving, head mounted displays (HMD) are being considered as a substitute visual cueing system. Recent innovations to virtual reality technologies are encouraging, however, differences between HMDs and more traditional visual displays have not been explored for all types of driving measures. In particular, while existing literature provides insight into the validity of HMDs as a substitute for higher fidelity visual displays in tests of driver behaviour and performance, there is a gap in the literature regarding differences in physiological responses. In the current study, upper body muscle activation and joint angle ranges were compared between an Oculus™ Rift Development Kit 2 HMD and a system of wrap around screens. Twenty-one participants each completed two simulated drives, one per display, in a counterbalanced order. During the simulation, drivers encountered unanticipated pedestrian crossings during which peak surface electromyography, root-mean-square of the surface electromyography signal and joint angles were determined bilaterally on the upper limbs. No significant differences (p ≤ 0.05) were observed between the Oculus™ Rift HMD and the wrap around screens for all dependent variables with the exception of left joint range of motion in female participants, suggesting that the HMD reduced field of view had a minimal effect on driver kinematics and no effect on muscle activation levels. Upper body bracing was observed during the hazard response time segments characterized by significantly increased muscle activity during hazard response time segments and minimal joint movement. Considering the lack of significant kinematic and muscle activation differences between the two visual inputs, HMD technology for hazard response may provide a suitable alternative to wrap around screens for studying kinematic responses during hazardous driving scenarios.

Analysis of Muscle Activity in the Sit-to-Stand Motion When Knee Movability is Disturbed

Sit-to-stand motion is an important daily activity, and disability of motion can significantly reduce quality of life. Therefore, it is important to understand the mechanism of sit-to-stand motion in order to prevent such scenarios. The sit-to-stand motion was found to be generated by four muscle groups, through muscle synergy. However, it is unclear how muscle synergy can be controlled. Human sit-to-stand motion may be planned based on body condition before motion. In this study, we aimed to clarify the relationship between body condition and muscle activity during the sit-to-stand motion. Accordingly, we measured the muscle activity when knee movability was disturbed as a condition of body change. We also measured the muscle activity during normal sit-to-stand motion and sit-to-stand motion with disturbed knee movability using surface electromyography. Subsequently, we extracted the muscle synergy from the measured muscle activity and compared the activity levels of muscle synergy. The results revealed that muscle activity contributing to forward bending increased and that contributing to the rise of the hip and stabilization decreased when knee movability was disturbed. These results suggest that humans compensate for disturbed knee movability with forward momentum and bending motion. Moreover, this implies that humans adjust their motion to various environments or body conditions by adjusting the level of forward bending activity.

Addition of a Cognitive Task During Walking Alters Lower Body Muscle Activity.

This study compared electromyography of five leg muscles during a single walking task (WALK) to a dual task (walking + cognitive task; COG) in 40 individuals (20M and 20F) using a wavelet analysis technique. It was hypothesized that muscle activation during the dual task would differ significantly from the walking task with respect to both timing (H1) and frequency (H2). The mean overall intensity for the COG trials was 4.1% lower for the tibialis anterior and 5.5% higher for the gastrocnemius medialis than in the WALK trials. The changes between the WALK and COG trials were short 50ms bursts that occurred within 100ms of heel strike in the tibialis anterior, and longer activation periods during the stance phase in the gastrocnemius medialis. No changes in overall intensity were observed in the peroneus longus, gastrocnemius lateralis, or soleus. Furthermore, no clear frequency bands within the signal could further characterize the overall changes in muscle activity during the COG task. This advances our understanding of how the division of attentional resources affects muscle activity in a healthy population of adults.

Specific features of blood parameters in volleyball players and wrestlers in preparatory period of training cycle

Annotation. Study of modern laboratory markers of structural and functional disturbances of muscle tissue in athletes, reflecting energy metabolism, paravertebral muscle damage, and being an indicator of body performance and muscle activity, is of undeniable practical importance for modern sports medicine. The aim of the study was to determine clinical and biochemical parameters of blood in volleyball players and wrestlers in assessment of structural and functional changes in skeletal muscles. Blood examination was carried out in 26 volleyball players and 25 middleweight Greco-Roman wrestlers as part of repeated comprehensive medical examination being conducted at the Department of Physical Education of Vinnytsia National Pirogov Memorial Medical University. Eligible subjects included athletes 17 to 21years of age having first adult category to master of sports and being in preparatory period of annual training macrocycle. The athletes were examined in the morning, on empty stomach, not less than 12 hours after training. The control group consisted of 25 practically healthy students having moderate physical activity. Clinical blood indices were determined by conductometric method on an automatic hematology analyzer ABX HORIBA PENTRA 60 C + (France). Hormonal studies were carried out by immunochemiluminescence method on automatic analyzer “ACCESS-2”, Bekchman Coulter (USA). Biochemical studies were performed using an automatic analyzer AU-480, Bekchman Coulter (USA). Electrolyte content was determined by ion-selective electrode technology on Medica electrolyte analyzer in EasyElectrolytes™, using lithium heparin vacuum system. Glucose levels were determined on automatic analyzer Biosen (Germany). Statistical processing was done using the program “Statistica 5.5”. Significance of differences between the variables was determined by Mann-Whitney U-test. The following serum humoral factors were found to be of great significance in assessment of structural and functional changes in skeletal muscles in volleyball players and wrestlers: the number of large immature cells of monocytes and platelets, electrolyte content, concentration of creatine phosphokinase and lactate dehydrogenase, creatinine level, as well as triglycerides and lactate levels. Establishing blood biomarkers should be an integral part of scientific and practical monitoring of health status in team athletes and wrestlers.

The Human Neck is Part of the Musculoskeletal Core: Cervical Muscles Help Stabilize the Pelvis During Running and Jumping.

SynopsisDuring locomotion, cervical muscles must be active to stabilize the head as the body accelerates and decelerates. We hypothesized that cervical muscles are also part of the linked chain of axial muscles that provide core stabilization against torques applied to the hip joint by the extrinsic muscles of the legs. To test whether specific cervical muscles play a role in postural stabilization of the head and/or core stabilization of the pelvic girdle, we used surface electromyography to measure changes in muscle activity in response to force manipulations during constant speed running and maximum effort counter-movement jumps. We found that doubling the mass of the head during both running and maximum effort jumping had little or no effect on (1) acceleration of the body and (2) cervical muscle activity. Application of horizontal forward and rearward directed forces at the pelvis during running tripled mean fore and aft accelerations, thereby increasing both the pitching moments on the head and flexion and extension torques applied to the hip. These manipulations primarily resulted in increases in cervical muscle activity that is appropriate for core stabilization of the pelvis. Additionally, when subjects jumped maximally with an applied downward directed force that reduced acceleration and therefore need for cervical muscles to stabilize the head, cervical muscle activity did not decrease. These results suggest that during locomotion, rather than acting to stabilize the head against the effects of inertia, the superficial muscles of the neck monitored in this study help to stabilize the pelvis against torques imposed by the extrinsic muscles of the legs at the hip joint. We suggest that a division of labor may exist between deep cervical muscles that presumably provide postural stabilization of the head versus superficial cervical muscles that provide core stabilization against torques applied to the pelvic and pectoral girdles by the extrinsic appendicular muscles.

Comparison of Shoulder Kinematics and Muscle Activation of Female Elite Handball Players With and Without Pain-An Explorative Cross-Sectional Study.

Non-traumatic shoulder injuries are common in team handball. However, many athletes continue to throw, despite pain in the shoulder. This study investigated upper body kinematics and muscle activation while throwing in female elite handball players with and without shoulder pain. Thirty female elite team handball players, 15 with pain (age 22.2 ± 2.9 yrs.) and 15 without pain (age 20.4 ± 2.6 yrs.) performed five standing throws in which joint kinematics and muscle activity were measured in the following muscles: pectoralis major, infraspinatus, serratus anterior, latissimus dorsi, and upper-, middle-, and lower trapezius. The main findings revealed that peak joint angles and angular velocities were not different between groups; however, group differences were observed in earlier timing of position and longer time spent in maximal shoulder extension and external shoulder rotation in the pain group compared with the no pain group. The pain group also revealed a significant lower muscle peak activity in the serratus anterior during the cocking phase compared to the no pain group. After the cocking phase and at ball release, the groups had similar activation. In conclusion, the present study showed group differences in appearance and time spent in maximal humerus extension and external rotation and a different serratus anterior muscle peak activity between elite handball players playing with and without shoulder pain, which are identified as possible mechanisms of adaptation to avoid pain.

Undulatory Swimming Performance Explored With a Biorobotic Fish and Measured by Soft Sensors and Particle Image Velocimetry.

Due to the difficulty of manipulating muscle activation in live, freely swimming fish, a thorough examination of the body kinematics, propulsive performance, and muscle activity patterns in fish during undulatory swimming motion has not been conducted. We propose to use soft robotic model animals as experimental platforms to address biomechanics questions and acquire understanding into subcarangiform fish swimming behavior. We extend previous research on a bio-inspired soft robotic fish equipped with two pneumatic actuators and soft strain sensors to investigate swimming performance in undulation frequencies between 0.3 and 0.7 Hz and flow rates ranging from 0 to 20 in a recirculating flow tank. We demonstrate the potential of eutectic gallium–indium (eGaIn) sensors to measure the lateral deflection of a robotic fish in real time, a controller that is able to keep a constant undulatory amplitude in varying flow conditions, as well as using Particle Image Velocimetry (PIV) to characterizing swimming performance across a range of flow speeds and give a qualitative measurement of thrust force exerted by the physical platform without the need of externally attached force sensors. A detailed wake structure was then analyzed with Dynamic Mode Decomposition (DMD) to highlight different wave modes present in the robot’s swimming motion and provide insights into the efficiency of the robotic swimmer. In the future, we anticipate 3D-PIV with DMD serving as a global framework for comparing the performance of diverse bio-inspired swimming robots against a variety of swimming animals.