Neuromuscular Control

In this study, the effects of mental fatigue on mechanically induced tremor at both a low (3-6 Hz) and high (8-12 Hz) frequency were investigated. The two distinct tremor frequencies were evoked using two springs of different stiffness, during 20 s sustained contractions of the knee extensor muscles at 30% maximum voluntary contraction (MVC) before and after 100 min of a mental fatigue task, in 12 healthy (29 ± 3.7 years) participants. Mental fatigue resulted in a 6.9% decrease in MVC and in a 9.4% decrease in the amplitude of the agonist muscle EMG during sustained 30% MVC contractions in the induced high frequency only. Following the mental fatigue task, the coefficient of variation and standard deviation of the force signal decreased at 8-12 Hz induced tremor by 31.7% and 35.2% respectively, but not at 3-6 Hz induced tremor. Similarly, the maximum value and area underneath the peak in the power spectrum of the force signal decreased by 55.5% and 53.1% respectively in the 8-12 Hz range only. In conclusion, mental fatigue decreased mechanically induced 8-12 Hz tremor and had no effect on induced 3-6 Hz tremor. We suggest that the reduction could be attributed to the decreased activation of the agonist muscles.

Purpose The effects of low-intensity exercise, heat-induced hypo-hydration and rehydration on maximal strength and the underlying neurophysiological mechanisms are not well understood. Methods To assess this, 12 participants took part in a randomised crossover study, in a prolonged (3 h) submaximal (60 W) cycling protocol under 3 conditions: (i) in 45 °C (achieving ~ 5% body mass reduction), with post-exercise rehydration in 2 h (RHY2), (ii) with rehydration across 24 h (RHY24), and (iii) a euhydrated trial in 25 °C (CON). Dependent variables included maximal voluntary contractions (MVC), maximum motor unit potential (M MAX), motor evoked potential (MEP RAW) amplitude and cortical silent period (cSP) duration. Blood-brain-barrier integrity was also assessed by serum Ubiquitin Carboxyl-terminal Hydrolase (UCH-L1) concentrations. All measures were obtained immediately pre, post, post 2 h and 24 h. Results During both dehydration trials, MVC (RHY2: p < 0.001, RHY24: p = 0.001) and MEP RAW (RHY2: p = 0.025, RHY24: p = 0.045) decreased from pre-to post-exercise. MEP RAW returned to baseline during RHY2 and CON, but not RHY24 (p = 0.020). MEP/M MAX ratio decreased across time for all trials (p = 0.009) and returned to baseline, except RHY24 (p < 0.026). Increased cSP (p = 0.011) was observed during CON post-exercise, but not during RHY2 and RHY24. Serum UCH-L1 increased across time for all conditions (p < 0.001) but was not significantly different between conditions. Conclusion Our findings demonstrate an increase in corticospinal inhibition after exercise with fluid ingestion, but a decrease in corticospinal excitability after heat-induced hypo-hydration. In addition, low-intensity exercise increases peripheral markers of blood-brain-barrier permeability. Communicated by George Havenith.

Throughout the human life span the functions of several physiological systems dramatically change, including proprioception. Impaired proprioception leads to less accurate detection of body position changes increasing the risk of fall, and to abnormal joint biomechanics during functional activities so, over a period of time, degenerative joint disease may result. Altered neuromuscular control of the lower limb and consequently poor balance resulting from changes in the proprioceptive function could be related to the high incidence of harmful falls that occur in old age subjects. There is evidence of proprioception deterioration with aging. Regular physical activity seems to be a beneficial strategy to preserve proprioception and prevent falls among older subjects. Some studies have demonstrated that the regular physical activity can attenuate age-related decline in proprioception. This paper reviews the evidence of age effects on joint proprioception. We will discuss the possible me...

Shoulder dysfunction inhibits 80% of competitive swimmers from performing optimally. The most common contributing factor to shoulder dysfunction is an altered scapula position. A standard for the distance between T4 and the medial border of the scapula is lacking. Measurements of the distance between T4 and the root of the scapula were made and the relationship of the distance and the function of trapezius middle fibres at resting length was tested. A Vernier caliper ®  (ICC 0.94) was used to measure the distance from T4 to the medial border of the scapula. Exercises and stretches to retrain and strengthen the middle fibres of the trapezius specifically were performed twice a week, scheduled around the swimmers’ regular training and strengthening sessions, for six weeks. The results showed that palpation of the scapula to measure the distance between T4 and the spinal root is reliable and valid. A normalisation index should be used to adjust for body build and posture. Furthermore, ...

Background: Cervical Radiculopathy (CR) involves nerve root compression in the cervical spine, leading to radiating pain and neurological deficits. Traditional conservative treatments like physical therapy focus on symptom management, while neural mobilization (NM) techniques aim to improve neural mobility directly. Objective: This study compares the effectiveness of neural mobilization techniques with traditional conservative treatment in reducing pain, improving range of motion (ROM), and functional disability in patients with cervical radiculopathy. Methods: Sixty patients with CR were randomly divided into two groups: Group A received neural mobilization, and Group B received traditional physiotherapy. Outcome measures included Visual Analog Scale (VAS) for pain, Neck Disability Index (NDI) for functional disability, and goniometric ROM measurements. Assessments were conducted at baseline, postintervention, and follow-ups at 4, 8, and 12 weeks. Results: Group A exhibited significantly greater reductions in pain, better improvements in functional disability (NDI), and ROM at all follow-up intervals (p < 0.001). Adverse events were more frequent in Group B. Conclusion: Neural mobilization is more effective than traditional physiotherapy in managing cervical radiculopathy and should be considered as a first-line treatment.

The deleterious effects of anoxia followed by reperfusion with oxygen in higher animals including mammals are well known. A convenient and genetically well characterized small-animal model that exhibits reproducible, quantifiable oxygen reperfusion damage is currently lacking. Here we describe the dynamics of whole-organism metabolic recovery from anoxia in an insect, Drosophila melanogaster, and report that damage caused by oxygen reperfusion can be quantified in a novel but straightforward way. We monitored CO 2 emission (an index of mitochondrial activity) and water vapor output (an index of neuromuscular control of the spiracles, which are valves between the outside air and the insect's tracheal system) during entry into, and recovery from, rapid-onset anoxia exposure with durations ranging from 7.5 to 120 minutes. Anoxia caused a brief peak of CO 2 output followed by knockout. Mitochondrial respiration ceased and the spiracle constrictor muscles relaxed, but then re-contracted, presumably powered by anaerobic processes. Reperfusion to sustained normoxia caused a bimodal reactivation of mitochondrial respiration, and in the case of the spiracle constrictor muscles, slow inactivation followed by reactivation. After long anoxia durations, both the bimodality of mitochondrial reactivation and the recovery of spiracular control were impaired. Repeated reperfusion followed by episodes of anoxia depressed mitochondrial respiratory flux rates and damaged the integrity of the spiracular control system in a dose-dependent fashion. This is the first time that physiological evidence of oxygen reperfusion damage has been described in an insect or any invertebrate. We suggest that some of the traditional approaches of insect respiratory biology, such as quantifying respiratory water loss, may facilitate using D. melanogaster as a convenient, well-characterized experimental model for studying the underlying biology and mechanisms of ischemia and reperfusion damage and its possible mitigation.

Anterior Cruciate Ligament (ACL) injuries are a prevalent concern
in athletic population, particularly among female athletes who are
disproportionately affected. The increased incidence of ACL injuries
in females is attributed to a combination of anatomical, physiological,
and biomechanical factors that influence knee stability. This review
comprehensively explores these contributing factors, highlighting genderspecific anatomical differences such as wider pelvis, increased quadriceps
(Q) angle, and steeper tibial slopes, all of which predispose females to
greater knee valgus during dynamic activities.

The purpose of this study was to investigate the impacts of regular Tai Chi (TC) exercise on neuromuscular reaction in old people. 21 old TC practitioners with regular practicing TC for more than 4 year and 22 sedentary non-practitioners were recruited to respectively form the TC group and sedentary control group. Electromyography (EiViG) was used to detect the neuromuscular reaction of the leg muscles to an unexpected ankle inversion perturbation. The latency of muscles, defined as the time from the moment of perturbation begins to the first EMG response (i.e. onset), was evaluated. The results indicated that regular TC practitioners activated their rectus femoris and anterior tibialis muscles to an unexpected perturbation significantly faster than their sedentary counterparts, which might be helpful for timely correction of postural disturbances.

Jumping on an elastic surface produces a number of sensory and motor adjustments. This effect caused by jumping on the trampoline has been called ''trampoline aftereffect''. The objective of the present study was to investigate the neuromuscular response related with this effect. A group of 15 subjects took part in an experimental session, where simultaneous biomechanical and electromyographic (EMG) recordings were performed during the execution of maximal countermovement jumps (CMJs) before and after jumping on an elastic surface. We assessed motor performance (leg stiffness, jump height, peak force, vertical motion of center of mass and stored and returned energy) and EMG activation patterns of the leg muscles. The results showed a significant increase (p 6 0.05) of the RMS EMG of knee extensors during the eccentric phase of the jump performed immediately after the exposure phase to the elastic surface (CMJ 1), and a significant increase (p 6 0.05) in the levels of co-activation of the muscles crossing the ankle joint during the concentric phase of the same jump. Results related with motor performance of CMJ 1 showed a significant increase in the leg stiffness (p 6 0.01) due to a lower vertical motion of center of mass (CoM) (p 6 0.005), a significant decrease in jump height (p 6 0.01), and a significantly smaller stored and returned energy (p 6 0.01). The changes found during the execution of CMJ 1 may result from a mismatch between sensory feedback and the efferent copy.

Using a padded landing surface during step aerobics has the potential to both reduce impact forces and increase energy cost. Eleven college-aged females performed 8-min trials [2-min of each step: basic step, alternate lead (AL), knee raise (KR), and step kick (SK)] on three surfaces. Surface conditions were uncovered force platform (FP) and FP covered with each of two different pads of medium-density foam [0.025 m (Thick) & 0.010 m (Thin)]. Data for oxygen consumption (VO 2), heart rate (HR), ratings of perceived exertion (RPE), maximum vertical ground reaction force (VGRF), rear-foot motion, and time of foot contact (TFC) were collected and a landing surface questionnaire was administered to obtain subjective perceptions of surfaces. Two-way repeated measures ANOVAs (STEP [3] × SURFACE [3]) were calculated. There were no significant differences for any variables among the surfaces. Significant differences were detected for VO 2 (AL<KR,SK), HR (AL<KR<SK), ROM (AL>SK), and TFC (AL>KR,SK) among the step movements. Subjects preferred stepping on the thick pad, felt less safe on the thin pad, and perceived more lower extremity stress landing on the uncovered force platform. The addition of two different density padded surfaces to the surfaces of two force platforms did not elicit differences in physiological or biomechanical force variables during 8 min of different actions used in step aerobics.

Postural control typically must be coordinated in a way that is functional with regard to the control of ulterior actions. This entails the formation of coordinative structures that are appropriately flexible and, in general, the incorporation of contributions from the vestibular, visual, and proprioceptive systems. Ballet dancers are known to exhibit heightened proprioceptive awareness and enhanced levels of postural control. However, it is not known if these are related, and the coordination of dancers' body segments during balance has never been examined. The present study utilized a visual tracking task in which participants tracked the foreaft motion of a virtual target, by standing on one leg and swaying so as to maintain an equal distance between their head and the target at all times, at frequencies of 0.20 and 0.60 Hz. Mean and SD relative phase between the ankle and hip joints were used to index coordination stability during task performance. Coordination stability during this task is generally believed to depend on proprioceptive coupling of rhythmic excursions about the ankle and hip. A joint-position matching task was used to assess proprioceptive awareness for the ankle, knee, and hip joints of both legs. An eyes-closed, quiet-standing task was also employed. Results showed that the dancers exhibited greater proprioceptive awareness in their lower limbs, and were also less variable in their ankle-hip coordination during the dynamic postural coordination task. Additionally, dancers exhibited lower determinism in the coupling between ankle and hip oscillations than controls. These results demonstrate that dancers are more sensitive to proprioceptive information in their lower limbs, and this may be an underlying mechanism driving their increased coordination stability. Dancers, through training and experience, may have become proficient at optimizing the constraints that enable them to perform complex balance tasks.

Astronauts adopt a variety of neuromuscular control strategies during space flight that are appropriate for locomoting in that unique environment, but are less than optimal upon return to Earth. We report here the first systematic investigation of potential adaptations in neuromuscular activity patterns associated with postflight locomotion. Astronaut-subjects were tasked with walking on a treadmill at 6.4 km/h while fixating a visual target 30 cm away from their eyes after space flights of 8-15 days. Surface electromyography was collected from selected lower limb muscles and normalized with regard to mean amplitude and temporal relation to heel strike. In general, high correlations (more than 0.80) were found between preflight and postflight activation waveforms for each muscle and each subject; however, relative activation amplitude around heel strike and toe off was changed as a result of flight. The level of muscle cocontraction and activation variability, and the relationship between the phasic characteristics of the ankle musculature in preparation for toe off also were altered by space flight. Subjects also reported oscillopsia during treadmill walking after flight. These findings indicate that, after space flight, the sensory-motor system can generate neuromuscular-activation strategies that permit treadmill walking, but subtle changes in lower-limb neuromuscular activation are present that may contribute to increased lower limb kinematic variability and oscillopsia also present during postflight walking.

Objective: The objective of this study was to determine the association between biomechanical and neuromuscular factors of clinically diagnosed mild to moderate knee osteoarthritis (OA) with radiographic severity and pain severity separately. Method: Three-dimensional gait analysis and electromyography were performed on a group of 40 participants with clinically diagnosed mild to moderate medial knee OA. Associations between radiographic severity, defined using a visual analog radiographic score, and pain severity, defined with the pain subscale of the WOMAC osteoarthritis index, with knee joint kinematics and kinetics, electromyography patterns of periarticular knee muscles, BMI and gait speed were determined with correlation analyses. Multiple linear regression analyses of radiographic and pain severity were also explored. Results: Statistically significant correlations between radiographic severity and the overall magnitude of the knee adduction moment during stance (r 2 ¼ 21.4%, P ¼ 0.003) and the magnitude of the knee flexion angle during the gait cycle (r 2 ¼ 11.4%, P ¼ 0.03) were found. Significant correlations between pain and gait speed (r 2 ¼ 28.2%, P < 0.0001), the activation patterns of the lateral gastrocnemius (r 2 ¼ 16.6%, P ¼ 0.009) and the medial hamstring (r 2 ¼ 10.3%, P ¼ 0.04) during gait were found. The combination of the magnitude of the knee adduction moment during stance and BMI explained a significant portion of the variability in radiographic severity (R 2 ¼ 27.1%, P < 0.0001). No multivariate model explained pain severity better than gait speed alone. Conclusions: This study suggests that some knee joint biomechanical variables are associated with structural knee OA severity measured from radiographs in clinically diagnosed mild to moderate levels of disease, but that pain severity is only reflected in gait speed and neuromuscular activation patterns. A combination of the knee adduction moment and BMI better explained structural knee OA severity than any individual factor alone.

Ankle sprains are common in netball and, if quantified mechanical ankle laxity can be linked with ankle kinematics during common netball landing tasks, then preventative measures can be implemented to reduce the occurrence of such injuries. Four netball players had their ankle laxity measured with an ankle arthrometer and performed two landing tasks (a cutting manoeuvre and a linear running task involving a ball catch and sudden stop) within the 3D motion analysis laboratory. The participant with the highest arthrometry measured ankle laxity angle displayed the highest frontal plane range of motion during both landing tasks. A high correlation coefficient (R 2 =0.84) was found when comparing arthrometry measures with frontal plane range of motion during the cutting task. Although a promising relationship was observed, larger sample sizes are needed for more conclusive results.

The aim of this study was to compare the bilateral electric activity of the rectus femoris (RF) and biceps femoris long head (BF) muscles during flexion and extension isotonic movements of the thigh and leg. Six men and six women accomplished all movements in 45° Leg Press apparatus with 30% and 60% of the maximum voluntary load (MVL). Electromyographic signs were captured using surface electrodes, recorded in a computerized electromyograph and analyzed in a system of data acquisition (Alc-EMG). The results demonstrated that the RF muscle showed greater electric activity than BF in both loads (30% and 60% MVL) and sides, regardless the sex. It can be concluded that in spite of the RF and BF muscles are in opposite ends of the hip and knee joints and are mentioned traditionally as antagonistic muscles, both muscles seem to act with synergism between themselves with predominance of the activation of the RF muscle on the BF muscle in both genders and studied loads in leg press 45 o execution. In addition, the electrical activity of these muscles is directly proportional to the load, independently of the sex.

The present review covers current knowledge about the ageing of oral physiology related to mastication and its effects on eating behaviour. Mastication is the first process undergone by a food during feeding. It has a key role in the maintenance of nutritional status in two respects. First, the perceptions of food&#39;s sensory properties elicited during chewing and swallowing are one of the major determinants of the pleasure which drives us to eat; second, the properties of the swallowed bolus are affected by oral conditions and this may modulate the subsequent phases of digestion. Ageing in healthy dentate subjects induces moderate changes in oral physiology. Changes in neuromuscular activity are partly compensated by changes in chewing behaviour. No clear age effect is seen in texture perception, although this does impact on food bolus properties. In contrast, great alterations in both chewing behaviour and food bolus properties are observed when ageing is associated with a compr...

While the typical physical exposure to modern-day workers has changed from heavy to low level repetitive demands, there is limited research that examines light occupations. This study examined trunk muscle recruitment strategies in response to a simulated checkout operation. Surface electromyography and kinematic variables were recorded from 29 healthy subjects. Four principal patterns accounted for 95.3% of the variation. Significant differences in scores captured different strategies in response to reach conditions and external moment directions. Synergistic co-activation of ipsilateral back sites and differential activation among external oblique and erector spinae sites suggests that the central nervous system may control different regions of the trunk musculature to optimally account for asymmetrical demands. The strategy between the internal oblique and back extensor sites suggests that a specific co-activation strategy may be needed during lighter work. During low-load occupational tasks, several recruitment strategies were required to maintain spinal stability and account for changing external moments. Statement of Relevance: Different recruitment strategies found in response to changing external moments offer new insights into neuromuscular control for lighter work. Specifically, multiple trunk muscle sites interact in a complex manner, taking into account task specificity and individual variation that are valuable in workstation design, evaluating injury risk and estimating spinal loads.

While the typical physical exposure to modern-day workers has changed from heavy to low level repetitive demands, there is limited research that examines light occupations. This study examined trunk muscle recruitment strategies in response to a simulated checkout operation. Surface electromyography and kinematic variables were recorded from 29 healthy subjects. Four principal patterns accounted for 95.3% of the variation. Significant differences in scores captured different strategies in response to reach conditions and external moment directions. Synergistic co-activation of ipsilateral back sites and differential activation among external oblique and erector spinae sites suggests that the central nervous system may control different regions of the trunk musculature to optimally account for asymmetrical demands. The strategy between the internal oblique and back extensor sites suggests that a specific co-activation strategy may be needed during lighter work. During low-load occupational tasks, several recruitment strategies were required to maintain spinal stability and account for changing external moments. Statement of Relevance: Different recruitment strategies found in response to changing external moments offer new insights into neuromuscular control for lighter work. Specifically, multiple trunk muscle sites interact in a complex manner, taking into account task specificity and individual variation that are valuable in workstation design, evaluating injury risk and estimating spinal loads.

Tracking the movement of the muscle-tendon junction is important for quantifying how muscles and tendons drive human movement. However, this remains an arduous task. Deep learning methods have recently shown promise for tracking, but there are limits to how well these networks generalize to novels subjects and tasks. Muscle-tendon junction movement is dependent upon muscle activation and joint-level motion. Therefore, we sought to determine if supplementing current networks with ankle angle and electromyographical (EMG) data would improve tracking. We observed a 20% increase in tracking accuracy for novel subjects when we incorporated EMG and ankle angle data into a current deep-learning network. Our results indicate that extending current methods to include data beyond the ultrasound image can significantly improve their accuracy.

Postural control typically must be coordinated in a way that is functional with regard to the control of ulterior actions. This entails the formation of coordinative structures that are appropriately flexible and, in general, the incorporation of contributions from the vestibular, visual, and proprioceptive systems. Ballet dancers are known to exhibit heightened proprioceptive awareness and enhanced levels of postural control. However, it is not known if these are related, and the coordination of dancers' body segments during balance has never been examined. The present study utilized a visual tracking task in which participants tracked the foreaft motion of a virtual target, by standing on one leg and swaying so as to maintain an equal distance between their head and the target at all times, at frequencies of 0.20 and 0.60 Hz. Mean and SD relative phase between the ankle and hip joints were used to index coordination stability during task performance. Coordination stability during this task is generally believed to depend on proprioceptive coupling of rhythmic excursions about the ankle and hip. A joint-position matching task was used to assess proprioceptive awareness for the ankle, knee, and hip joints of both legs. An eyes-closed, quiet-standing task was also employed. Results showed that the dancers exhibited greater proprioceptive awareness in their lower limbs, and were also less variable in their ankle-hip coordination during the dynamic postural coordination task. Additionally, dancers exhibited lower determinism in the coupling between ankle and hip oscillations than controls. These results demonstrate that dancers are more sensitive to proprioceptive information in their lower limbs, and this may be an underlying mechanism driving their increased coordination stability. Dancers, through training and experience, may have become proficient at optimizing the constraints that enable them to perform complex balance tasks.

Causative insight into the link between important aspects of an athlete's kinematics and knee joint loading in potentially injurious landings remains limited. The aim of this simulation study was to develop insight into the intra-limb configuration contributions to sagittal plane knee joint loading in drop (0.46m) landings. Notably accentuated (up to a 1.53 N.m.kg-1) peak knee joint extensor moments (Mek) were incurred with increased ankle, knee and hip joint flexion across the landing phase. While the peak Mek was alleviated with reduced ankle and knee joint flexion, a marginal, participant-specific effect was evident with a similarly reduced hip joint flexion. The extended use of customised simulations to understand the unique role of each lower-extremity joint in the kinematic chain was warranted to inform injury prevention strategies.

early work will be used as the standard definition. Sherrington defined proprioception as the culmination of all neural inputs originating from joints, tendons, muscles, and associated deep tissue proprioceptors. These inputs are projected to the central nervous system for processing and ultimately result in the regulation of reflexes and motor control. This definition views proprioception primarily as a sensory activity, occurring along the afferent pathway. More recently, the definition of the proprioceptive system has been expanded to include the complex interaction between the sensory pathways and the motor pathway (efferent system). This system has come to be known as the sensorimotor system. 33 Neurophysiology of Proprioception and Neuromuscular Control of the Joint When a proprioceptive stimulus is presented to the body, input occurs at three separate locations, including the visual system, the vestibular system, and the peripheral mechanoreceptors (Fig 1). These peripheral mechanoreceptors are Fig 1. A flow chart of lower limb dynamic neuromuscular response to sensory receptor input is shown.

Currently, the majority of neural stimulation studies are limited to acute animal experiments due to lack of suitable implantable microstimulation devices. As an initial step to observe the long-term effects of neural stimulation, a system consisting of an external wireless controller and an implantable dual-channel microcontroller-based microstimulator for tripolar high frequency blocking was developed. The system is not only small in size, and thus suitable for short-term implantation, but also has sufficient current output parameter ranges to meet the demand for high frequency blocking experiments. Using this implantable microstimulator, a series of experiments were conducted on New Zealand rabbit's tibial nerve, including frequency and amplitude selection in driving stimulus and blocking effect tests, which were designed to assess the feasibility and efficiency of the device via torque measurements. Our results showed that the implantable microstimulator system gave a satisfactory performance and could be utilized to achieve selective stimulation and blocking on various sizes of nerve fibers. Our implantable microstimulation system is not only a novel tool for neuromuscular control studies but could also provide a basis for developing various types of sophisticated neural prostheses.

No objective criteria exist for progressing athletes into cutting manoeuvres following ACL reconstruction (ACLR). The purpose of this study was to evaluate the relationship between a jump-cut task (JC) and the single-limb squat (SLS) in both ACLR and healthy controls. Case-control, laboratory based. Twenty-three participants with a history of ACLR (Age = 21 ± 3 years; Height = 174.5 ± 7.2 cm; Mass = 76.2 ± 9.9 kg) and 23 healthy controls participants (Age = 21 ± 3 years; Height = 173.8 ± 9.2 cm; Mass = 75.0 ± 10.5 kg) were included. Kinematics were collected bilaterally. Correlations between tasks were evaluated for kinematics. Independent sample t-tests were used to evaluate differences between groups for each dependent variable. Peak trunk rotation and medial knee displacement were strongly correlated (p < 0.001, r 2 = 0.63), between tasks. ACLR group performed SLS and JC tasks with less sagittal plane motion compared to healthy controls (p < 0.05). Lack of frontal and transverse plane control during SLS resulted in positions of increased lateral trunk flexion, hip adduction, and medial knee displacement during JC. The SLS may be considered for use as a clinical predictor of JC during rehabilitation following ACLR.

The aim of this study was to investigate if there is a common behaviour distinguishing subjects with stable ankles from those with unstable ankles. Therefore the muscular response and the ground reaction forces (GRF) of 24 subjects performing horizontal jumps and also drop landings from a 40cm high box, on three different surfaces (a level one and two surfaces inclined 3° either laterally or medially) were measured. Eight parameters of the EMG signals from each of six muscles of the lower leg and several GRF parameters (eight for jumping and seven for landing) were analysed. EMG data reveal that stable subjects have higher mean power frequencies (MPF), whereas unstable subjects increase their amplitudes. The GRFs show significant differences (p&lt;0.05) for the 2nd vertical force maximum (Fz2) and its slope (Fz2slope), for the contact time (CT) and for the force maximum in medial direction (FYmin) The one-legged horizontal jumping task, as well as the inclined ground conditions, see...

BACKGROUND Menopause is an aging process of the female reproductive system characterized by reduced estrogen levels. This results in increased osteoclastic activity, causing increased bone resorption and thus reduced bone mineral density (BMD). In addition to being influenced by osteoclastic activity, BMD of the lumbar vertebrae is also affected by the erector spinae muscle. The purpose of this study was to determine an association between postural scoliosis and erector spinae muscle endurance and its relation to BMD in postmenopausal women. METHODS This was a cross-sectional study conducted on postmenopausal women, who were selected by simple random sampling among residents of Mampang Prapatan subdistrict. The postural abnormality of scoliosis was determined by physical examnation, while erector spinae muscle endurance time was assessed using a modified Biering-Sorensen technique, and BMD was measured by bone mineral densitometry, to categorize into normal, osteopenia, and osteoporosis. RESULTS A total of 213 postmenopausal women with mean age of 53.52 ± 3.64 years participated in the study. The prevalence of scoliosis was 54.0%, and osteoporosis was 38.1%. The prevalence of osteoporosis was higher in women with scoliosis (48.7%) in comparison with those without scoliosis (31.6%) (p=0.411). In postmenopausal women with strong erector spinae muscle endurance the risk of of scoliosis was lower (0.76;95% Confidence Interval = 0.58-0.99) CONCLUSIONS In post menopausal women with postural scoliosis found a higher incidence of osteoporosis. High endurance of erector spinae muscle lowers the risk of scoliosis. Exercise to improve posture and increase endurance of erector spinae muscle need to be done to prevent decline of BMD.

The present study utilized high-impact supra-maximal landings to examine the influence of the pre-impact force level on the post-impact electromyographic (EMG) activity and, in particular, on the short latency EMG reflex (SLR) component. Unilateral-leg landings were performed in a sitting position on a sledge apparatus after release from high, but individually constant dropping height. A lower limb guiding device fixed to the front of the sledge seat allowed the subjects to sustain a given pre-set force level up to impact. This force level was either freely chosen or set at 20, 35, and 50% of maximal isometric plantarflexion force. EMG activity was recorded from eight major lower limb muscles. It was expected that the increase in the pre-impact force level would require the intervention of a protective neural strategy during the post-impact phase that would attenuate the SLR amplitude. The ultrasonography recordings confirmed that the soleus fascicles were stretched to induce SLR. T...

Background Lack of the neuromuscular control during locomotion in the knee joint leads to an increased risk of anterior cruciate ligament (ACL) injury in children. Hence, we aimed to explore the effects of a repetitive, model-oriented, and self-organized approach on lower limb kinematics during gait in children. Methods In randomized controlled trial, 36 children with 4 ± 0.79 years of age from the children gym were randomly (a lottery method) allocated into three groups, including (1) the model-oriented (n = 10), (2) Differential Learning (n = 11), and (3) control (n = 10) groups. Kinematic data of hip, knee, and ankle joints in the sagittal plane were recorded by a GoPro camera at the moments of heel-ground contact and toe-off the ground before and after a 6-week intervention (two sessions per week). Results The results indicate a 35% post-intervention increase of ankle dorsiflexion (95% CI: − 5.63 _ − 0.96) in the moment of heel-ground contact in the model-oriented group; however...

espanolEl objetivo de este estudio fue evaluar el seguimiento de la masa grasa y masa magra de los segmentos corporales de brazos y piernas de ambas extremidades en futbolistas juveniles profesionales. Se llevo a cabo un estudio longitudinal a 41 futbolistas (15.85 ± 0.98 anos de edad), realizando una medicion inicial (MI) y despues de 6 meses una medicion final (MF), utilizando el equipo de absorciometro dual de rayos X (DEXA). Se utilizo la prueba de t-student del programa SPSS (version 21.0). La masa magra de los brazos total lograron un aumento significativo (p EnglishThe objective of this study was to evaluate the follow-up of fat mass and lean mass of the body segments of the arms and legs in young professional soccer players. A longitudinal study was held to 41 players (15.85 ± 0.98 years old), performing an initial measurement (MI) and after 6 months a final measurement (MF), using the dual absorptiometer x-rays equipment (DEXA). The program SPSS t-student test (version 21.0...

Background: Muscle strength of the involved limb is known to be decreased after injury. Comparison with the uninvolved limb has become standard of practice to measure progress and for calculation of limb symmetry indices (LSIs) to determine readiness to return to sport. However, some literature suggests strength changes in the uninvolved limb also are present after lower extremity injury. Purpose: To examine the uninvolved limb strength in a population of adolescent athletes after an anterior cruciate ligament (ACL) injury and compare strength values with those of the dominant limb in a healthy control group.

The aim of this study was to investigate if there is a common behaviour distinguishing subjects with stable ankles from those with unstable ankles. Therefore the muscular response and the ground reaction forces (GRF) of 24 subjects performing horizontal jumps and also drop landings from a 40cm high box, on three different surfaces (a level one and two surfaces inclined 3° either laterally or medially) were measured. Eight parameters of the EMG signals from each of six muscles of the lower leg and several GRF parameters (eight for jumping and seven for landing) were analysed. EMG data reveal that stable subjects have higher mean power frequencies (MPF), whereas unstable subjects increase their amplitudes. The GRFs show significant differences (p&lt;0.05) for the 2nd vertical force maximum (Fz2) and its slope (Fz2slope), for the contact time (CT) and for the force maximum in medial direction (FYmin) The one-legged horizontal jumping task, as well as the inclined ground conditions, see...

Limb asymmetries in loading and movement patterns persist up to 2 years after anterior cruciate ligament reconstruction (ACLR) and are related to re-injury risk. PURPOSE: To determine changes in limb asymmetry across the first year following ACLR. METHODS: 23 adolescent ACLR athletes participated in the study (14 female, 9 male). Movement and loading mechanics were collected using an 8 camera motion capture system (120Hz) and 2 embedded force plates (2400Hz) during five vertical stop-jump trials. All analyses were completed using the MIXED models ANOVA procedure in SAS (version 9.3, Cary, NC), with a type I error rate of α=0.05. RESULTS: An interaction between time and surgical limb was observed for the peak knee extension moment (KEM) (p=0.041) with the surgical (Sx) and non-surgical (NSx) limbs converging across time (Figure 1). When examining side-to-side symmetry, there were no differences in frontal plane knee range of motion (ROM), sagittal plane hip ROM, and sagittal plane knee angle at contact independent of time. For the peak vertical ground reaction force (GRF) (p<0.001), impulse (p<0.001), limb stiffness (p<0.001), peak posterior GRF (p<0.001), and peak knee flexion angle (p=0.049) the NSx side demonstrated an increased value when compared to the Sx side. The peak vertical GRF and impulse were asymmetric up to 12 months after ACLR. However, loading rate and peak posterior GRF demonstrated asymmetry up to 6 months after ACLR, while limb stiffness asymmetry perpetuated until 5 months after ACLR. CONCLUSIONS: Movement and load asymmetry remain up to 12 months following surgery indicating that these patients are at risk for subsequent injuries even after being released to return to sports. Additional therapeutic interventions need to be implemented to restore symmetry and improve landing mechanics prior to athletes being return to sports. Figure 1: Peak knee extension moment differences between limbs and across time

The anterior cruciate ligament is the most commonly disrupted ligament in the knee in high-performance athletes. Most recently, advancements in surgical technique and graft fixation have enabled athletes to participate in early postoperative rehabilitation, focusing on range of motion and progressing to patellar mobilization, strengthening, and neuromuscular control. Several rehabilitation protocols exist with variations in specific exercises, progression through phases, and key components. The ultimate goal of rehabilitation is to return the athlete to preinjury performance level, including motion and strength, without injuring or elongating the graft. Each athlete is unique; thus, safe return to play should be individualized rather than follow a particular postoperative month or time line. This article provides an overview of the application and the scientific basis for formulating a rehabilitation protocol prior to and following anterior cruciate ligament surgery. [ Orthopedics. ...

In bivalves, water-pumping potential is determined both by ciliary activity and by the geometry of the system of passageways that acts as a conduit for water flow. Smooth muscles intrinsic to the gills of eulamellibranch bivalves possess the anatomical organization needed to regulate the dimensions of these water passageways. The tone of these muscles can be controlled experimentally using excitatory neurotransmitters to elicit muscle contraction and by removing Ca ++ from the Ringer's solution to induce muscular relaxation. These experimental methods were used to investigate the effects of smooth muscle tone on the gill dimensions of two freshwater bivalves, Dreissena polymorpha and Corbicula fliuninea, and one marine bivalve, Mercenaria mercenaries In addition, endoscopic observations were made from the suprabranchial chamber of a freshwater unionid, Lampsilis anodontoides. Contraction of gill muscles led to a significant reduction in interfilament width, internal ostial area, and the cross-sectional area of the water tubes. Endoscopic observation from minimally disturbed L. anodontoides revealed rapid constriction of the water tubes upon contraction of the muscles of the gill and gill axis. Taken together, these data support the idea that alteration of smooth muscle tone in the gill provides a mechanism for controlling water-pumping activities.

medialis (VM), vastus lateralis (VL), rectus femoris (RF), semitendinosus (ST), biceps femoris (BF), gastrocnemius medialis (GM), and gastrocnemius lateralis (GL) in both lower extremities. The maximal displacement, delay time, contraction time, sustained time, and half-relaxation time were obtained and compared between both sides. Results There were no significant differences in the vast majority of the TMG parameters between both lower extremities. The dominant side demonstrated higher VM contraction time (p = 0.008), RF sustained time (p = 0.009), RF half-relaxation time (p = 0.01), and BF sustained time (p = 0.04), but lower VL contraction time (p = 0.03) and VL delay time (p = 0.02) compared to the non-dominant side. Conclusion In general, TMG-assessed neuromuscular characteristics of the VM, VL, RF, ST, BF, GM, and GL were not affected by lower extremity dominance in male soccer players. Therefore, there is no need to assess both sides when using TMG to monitor the response to training or muscles at risk of injury in soccer players unless there is a specific reason. Level of evidence Prognostic study, Level II.

Purpose To synthesize the results of systematic literature review focused on the effectiveness of anterior cruciate ligament (ACL) injury prevention programmes in male athletes. Methods All abstracts and articles of potential interest identified through the systematic literature search were reviewed in detail to determine on inclusion status. Information regarding prevention programmes to reduce ACL injuries or to modify risk factors for ACL injuries in male athletes was systematically extracted and included intervention and study design, characteristics of participants, sport and level of competition, characteristics of prevention programmes, results, and conclusions. All studies were evaluated for methodological quality to assess the risk of bias. Results The principal findings of this systematic review are as follows: (1) most of the studies applied prevention

Beach handball is a growing sport without available scientific data on the type of injuries that occur. The aim of this study is to record the incidence rate, type and severity of injuries in this sport. During the finals of the European Beach Tour 2014, 122 beach handball players completed a self-report questionnaire about the injuries they had sustained during the previous 24 months. The injury incidence rate for male and female was 12/1000h and 11.36/1000h respectively during games, and 1.8/1000h and 4/1000h during training accordingly. Muscle strains were the most common type of injury, while the majority of injuries affected the knee. The return to sports period was within 2 weeks from injury for 62% of male and 64.5% of female athletes. Statistical analysis could not correlate the incidence or severity of injuries in beach handball to any of the analyzed variables. This study showed that injuries in beach handball are similar to team handball, rather than to other "sand" sports.

We used whole-head magnetoencephalography to investigate cortical activity during two oromotor activities foundational to speech production. 13 adults performed mouth opening and phoneme (/ pa/) production tasks to a visual cue. Jaw movements were tracked with an ultrasound-emitting device. Trials were time-locked to both stimulus onset and peak of jaw displacement. An eventrelated beamformer source reconstruction algorithm was used to detect areas of cortical activity for each condition. Beamformer output was submitted to iterative K-means clustering analyses. The time course of neural activity at each cluster centroid was computed for each individual and condition. Peaks were identified and latencies submitted for statistical analysis to reveal the relative timing of activity in each brain region. Stimulus locked activations for the mouth open task included a progression from left cuneus to left frontal and then right pre-central gyrus. Phoneme generation revealed the same sequence but with bilateral frontal activation. When time locked to jaw displacement, the mouth open condition showed left frontal followed by right frontal-temporal areas. Phoneme generation showed a complicated sequence of bilateral temporal and frontal areas. This study used three unique approaches (beamforming, clustering and jaw tracking) to demonstrate the temporal progression of neural activations that underlie the motor control of two simple oromotor tasks. These findings have implications for understanding clinical conditions with deficits in articulatory control or motor speech planning.

BACKGROUND: Even though literature indicates presence of weak hip abductors and lateral rotators' in Patellofemoral Pain (PFP), studies evaluating the effect of hip abductors and lateral rotators strengthening to improve knee function and quality of life in PFP are limited. OBJECTIVE: This study systematically reviews and meta-analyzes the best evidence on the therapeutic value of strengthening hip abductors and lateral rotators muscles for treating PFP with a presumptive hypothesis that strengthening hip muscles stabilizes the patellofemoral joint, relieves pain, and enhances knee functions. METHOD: Medline, EMBASE, CINAHL, PEDro and PubMed Central databases were searched between January 1994 and September 2019 using the PICOS tool. The methodological quality of the selected studies were appraised individually using the 20-item McMaster Critical Review Form for Quantitative Studies. Supplemental quality appraisal of randomized controlled clinical trials performed using the Cochrane Collaboration's 'Risk of bias' quality criteria. Data on patient population demographics, interventions, duration of intervention, and outcome measures were extracted and summarized in evidence tables and descriptive analysis. Meta-analyses under both fixed and random-effects models determined pooled effects size from appropriate RCTs. RESULTS: All fourteen studies demonstrated that hip muscle strengthening improved pain and knee function. All RCTs, except one, demonstrated that hip muscle strengthening is superior to quadriceps strengthening. Of the five RCTs assessing the additional effect of hip-quad versus quadriceps strengthening, four suggested that hip-quad strengthening is superior to standard quadriceps strengthening alone to improve PFP and knee function. CONCLUSION: In adult patients with PFP, strengthening hip abductors and lateral rotators' have beneficial therapeutic effects than the conventional quadriceps exercises in improving knee pain and function both in the short-and long term. However, the present review data can be used to develop a standardized hip-quad protocol in the future.

The purpose of the thesis was to evaluate the neuromuscular control of shoulder muscles when performing shoulder efforts concurrently with hand or elbow efforts in healthy and injured individuals. Of particular interest was the response of the supraspinatus and infraspinatus muscles to performing an additional hand task, such as targeted gripping, while also performing different shoulder actions. Prior to doing so, two studies were undertaken to provide the necessary groundwork for the remaining two studies of this thesis. The first study investigated whether changes to shoulder muscle activity previously seen with gripping where solely the result of the novelty of using feedback to regulate grip force. The results of this study suggested that the alterations in shoulder muscle activity with gripping are not diminished with repetition. The second study provided an improved method of normalizing electromyograms from dynamic contractions and was used in the subsequent studies of this thesis. Studies 3 and 4 of this thesis examined the response of shoulder muscles in healthy individuals during static submaximal efforts and maximal dynamic efforts in flexion and scapular planes with neutral and supinated forearm postures. Three conditions were tested in both studies: (i) no additional load, (ii) gripping to 30% of maximum and (iii) contracting the biceps to 30% of maximum. A prevailing theme found during sub-maximal contractions was individuality in neuromuscular recruitment strategies and precluded any significant effects of gripping or biceps contractions. During dynamic contractions, concurrent shoulder efforts with gripping and biceps contractions was found to significantly decrease iv deltoid, supraspinatus and infraspinatus muscle forces during flexion with supinated forearm posture. This thesis provided a thorough examination of shoulder electromyography in healthy individuals, improving our understanding of the neuromuscular control of the shoulder musculature. A common theme of this thesis was the individuality of neuromuscular strategies of the shoulder.

Requirements of a successful skier have changed during last decades due to e.g. changes in race forms and developments of equipment. The purpose of this thesis was to clarify in four Articles (I-IV) what are the requests modern skate skiing sets for the athletes in a biomechanical point of view. Firstly, it was explained how skiers control speed from low to maximal speeds (I). Secondly, the effects of long simulated ski race were determined with traditional force measurement methods (III) as well as with novel propulsion methods (IV). During the work process a need for updated multi-dimensional leg force sensor appeared and it was materialized (II). During the thesis 16 national level athletes participated in the different experiments of the study. Measurements for controlling speed were carried out with 3D force sensor for legs and pole force sensor for arms. Conventional cycle, force and joint kinematic parameters were analysed (I). After, a need for reliable force sensor appeared...

Context: The Landing Error Scoring System (LESS) is a two-dimensional landing technique assessment tool that is readily available to clinicians. However, the LESS merely assesses a contrived landing, rather than dynamic, complex movements that may occur during actual athletic performance. Objective: To compare the LESS scores and knee joint kinematics between the LESS vertical-drop jump (DVJ), and two simulated basketball landing performances, jump-stop jump shot (JS) and rebounding (RB).

The present study investigates the various physiological and mechanical techniques employed by archers of varying skill levels. A total number of four archers and non-medalist) and two males (expert and novice) participated in the study in two separate experiments. A sum of four shimmer sensors were used to examine, compare and differentiate the postural balance, movement of the bow, digitorum superficial and muscle extensor digitorum as well as the heart rate variability of the archers. The results revealed that elite and medalist archers are better in controlling their postural sway, reducing the movement of their bows, have greater activation of muscle extensors. Both medalist and elite archers maintained a lower heart rate, hence achieved consistency and maximum scores as opposed to the non

Forearm electromyographic (EMG) data are assumed to be an effective method in estimating performance level in archery. The aim of the current study was to establish archery skill indexes based on EMG data. Elite (n = 7, FITA score = 1303.4 ± 26.2), beginner (n = 6, FITA score = 1152 ± 9.0) and non-archers (n = 10, assumed FITA score = 250 0), were involved in the study. EMG activity of Muscle flexor digitorum superficialis and Muscle extensor digitorum were quantified. Two-second periods-1 s before and 1 s after the fall of the clicker-were used to obtain averaged and rectified EMG data. The averaged and rectified EMG data were filtered by averaging finite impulse response filter with 80 ms time window and then normalized with respect to maximum voluntary contraction. To estimate FITA scores from EMG data, the following skill indexes that based on mean area under some parts of processed EMG waveforms was offered for archery. These were the pre-clicker archery skill index (PreCASI), post-clicker archery skill index (PostCASI), archery skill index (ASI) and post-clicker archery skill index 2 (PostCASI2).The correlations between rank of FITA scores and natural logarithms of archery skill indexes were significant for log(PreCASI): r = À0.66, p < 0.0008; for log(PostCASI): r = À0.70, p < 0.0003; for log(ASI): r = À0.74, p < 0.0001; log(PostCASI2): r = À0.63, p < 0.002. It is concluded that EMG skill indexes may be useful for: (a) assessing shooting techniques, (b) evaluation of archersÕ progress and (c) selection of talented archers.