Changes In Muscle Activation Patterns Research Articles

Forelimb muscle activation patterns in American alligators: Insights into the evolution of limb posture and powered flight in archosaurs.

The evolution of archosaurs provides an important context for understanding the mechanisms behind major functional transformations in vertebrates, such as shifts from sprawling to erect limb posture and the acquisition of powered flight. While comparative anatomy and ichnology of extinct archosaurs have offered insights into musculoskeletal and gait changes associated with locomotor transitions, reconstructing the evolution of motor control requires data from extant species. However, the scarcity of electromyography (EMG) data from the forelimb, especially of crocodylians, has hindered understanding of neuromuscular evolution in archosaurs. Here, we present EMG data for nine forelimb muscles from American alligators during terrestrial locomotion. Our aim was to investigate the modulation of motor control across different limb postures and examine variations in motor control across phylogeny and locomotor modes. Among the nine muscles examined, m. pectoralis, the largest forelimb muscle and primary shoulder adductor, exhibited significantly smaller mean EMG amplitudes for steps in which the shoulder was more adducted (i.e., upright). This suggests that using a more adducted limb posture helps to reduce forelimb muscle force and work during stance. As larger alligators use a more adducted shoulder and hip posture, the sprawling to erect postural transition that occurred in the Triassic could be either the cause or consequence of the evolution of larger body size in archosaurs. Comparisons of EMG burst phases among tetrapods revealed that a bird and turtle, which have experienced major musculoskeletal transformations, displayed distinctive burst phases in comparison to those from an alligator and lizard. These results support the notion that major shifts in body plan and locomotor modes among sauropsid lineages were associated with significant changes in muscle activation patterns.

Whole-Body Adaptive Functional Electrical Stimulation Kinesitherapy Can Promote the Restoring of Physiological Muscle Synergies for Neurological Patients.

Background: Neurological diseases and traumas are major factors that may reduce motor functionality. Functional electrical stimulation is a technique that helps regain motor function, assisting patients in daily life activities and in rehabilitation practices. In this study, we evaluated the efficacy of a treatment based on whole-body Adaptive Functional Electrical Stimulation Kinesitherapy (AFESK™) with the use of muscle synergies, a well-established method for evaluation of motor coordination. The evaluation is performed on retrospectively gathered data of neurological patients executing whole-body movements before and after AFESK-based treatments. Methods: Twenty-four chronic neurologic patients and 9 healthy subjects were recruited in this study. The patient group was further subdivided in 3 subgroups: hemiplegic, tetraplegic and paraplegic. All patients underwent two acquisition sessions: before treatment and after a FES based rehabilitation treatment at the VIKTOR Physio Lab. Patients followed whole-body exercise protocols tailored to their needs. The control group of healthy subjects performed all movements in a single session and provided reference data for evaluating patients’ performance. sEMG was recorded on relevant muscles and muscle synergies were extracted for each patient’s EMG data and then compared to the ones extracted from the healthy volunteers. To evaluate the effect of the treatment, the motricity index was measured and patients’ extracted synergies were compared to the control group before and after treatment. Results: After the treatment, patients’ motricity index increased for many of the screened body segments. Muscle synergies were more similar to those of healthy people. Globally, the normalized synergy similarity in respect to the control group was 0.50 before the treatment and 0.60 after (p < 0.001), with improvements for each subgroup of patients. Conclusions: AFESK treatment induced favorable changes in muscle activation patterns in chronic neurologic patients, partially restoring muscular patterns similar to healthy people. The evaluation of the synergic relationships of muscle activity when performing test exercises allows to assess the results of rehabilitation measures in patients with impaired locomotor functions.

Motor Control Changes after Innovative Aquatic Proprioceptive Training in Athletes with Anterior Cruciate Ligament Reconstruction: Voluntary Response Index Analysis

Objectives: The main aim of this study was to determine and compare the effects of innovative aquatic proprioceptive training plus conventional rehabilitation with conventional rehabilitation alone on voluntary response index (VRI) components in athletes with anterior cruciate ligament reconstruction (ACLR). Methods: Forty male athletes with ACLR (18 - 35 years of age) voluntarily participated in this study. They were randomly allocated into two groups. The conventional therapy group (n = 20) underwent conventional rehabilitation for ten weeks, three sessions a week. The aquatic proprioceptive training plus conventional rehabilitation (n = 20) group received the same conventional rehabilitation plus 30 sessions of innovative hydrotherapy exercises. Voluntary response index analysis was carried out to determine changes in motor control and muscle activation patterns based on electromyographic (EMG) outcome measures. Results: There was a significant difference in the magnitude (MAG) and similarity index (SI) between the two groups at all phases of the functional task (sit-stand-sit) (P &lt; 0.05). Also, both groups showed a significant change in MAG and SI at all phases of the functional task (sit-stand-sit) after the intervention (P &lt; 0.05). Effect size in both groups for MAG and SI at all phases of the functional task (sit-stand-sit) ranged from 2.5 to 4.61 and from 0.29 to 1.7, respectively. Conclusions: The incorporation of innovative aquatic proprioceptive training into conventional accelerated rehabilitation protocol leads to changes in motor control due to changes in the muscle activation pattern after the intervention.

Acoustic pre-stimulation modulates startle and postural reactions during sudden release of standing support surface in aging.

Falls contribute to injuries and reduced level of physical activity in older adults. During falls, the abrupt sensation of moving downward triggers a startle-like reaction that may interfere with protective response movements necessary to maintain balance. Startle reaction could be dampened by sensory pre-stimulation delivered immediately before a startling stimulus. This study investigated the neuromodulatory effects of pre-stimulation on postural/startle responses to drop perturbations of the standing support surface in relation to age. Ten younger and 10 older adults stood quietly on an elevated computer-controlled moveable platform. At an unpredictable time, participants were dropped vertically to elicit a startle-like response. Reactive drop perturbation trials without a pre-stimulus (control) were alternated with trials with acoustic pre-stimulus tone (PSI). A two-way mixed design analysis of variance comparing condition (control vs. PSI) X group (younger vs. older) was performed to analyze changes in muscle activation patterns, ground reaction force, and joint angular displacements. Compared to younger adults, older adults showed lower neck muscle electromyography amplitude reduction rate and incidence of response. Peak muscle activation in neck, upper arm, and hamstring muscles were reduced during PSI trials compared to control trials in both groups (p<0.05). In addition, knee and hip joint flexion prior to ground contact was reduced in PSI trials compared to control (p<0.05). During post-landing balance recovery, increased knee and hip flexion displacement and time to peak impact force were observed in PSI trials compared to control condition (p<0.05). PSI reduced startle-induced muscle activation at proximal body segments and likely decreased joint flexion during abrupt downward vertical displacement perturbations of the body. Older adults retained the ability to modulate startle and postural responses but their neuromodulatory capacity was reduced compared with younger adults. Further research on the potential of applying PSI as a possible therapeutic tool to reduce the risk of fall-related injury is needed.

The effect of targeted resistance training on bench press performance and the alternation of prime mover muscle activation patterns

ABSTRACT Targeted muscle strengthening might improve performance or help overcome training stagnation; therefore, the aim of the present study was to investigate changes in muscle activity patterns before and after six weeks of targeted resistance training. Twenty-seven resistance-trained men were divided into three groups according to their prime mover activity, as measured by surface electromyography during a bench press (BP). Each group underwent a six-week block of targeted exercises for one of the following muscles: anterior deltoid (AD), pectoralis major (PM) or triceps brachii (TB). ANOVA showed that each group increased their 1 repetition maximum (1RM) (p < 0.05) and the activity of the exercised muscle group during an isometric bench press (p < 0.01) and during a dynamic bench press (p < 0.01) at 85% of the 1RM. During the isometric BP, the TB training group had an increase in TB activity in comparison to the other groups. Targeted muscle training is a useful method for muscle activity increase and increasing the maximum strength in complex exercise, when applied in activity-deficient muscle groups. Strengthening the TB elicits changes in all prime movers and results in TB activity domination during a bench press.

Non-negative matrix factorisation is the most appropriate method for extraction of muscle synergies in walking and running

Muscle synergies provide a simple description of a complex motor control mechanism. Synergies are extracted from muscle activation patterns using factorisation methods. Despite the availability of several factorisation methods in the literature, the most appropriate method for muscle synergy extraction is currently unknown. In this study, we compared four muscle synergy extraction methods: non-negative matrix factorisation, principal component analysis, independent component analysis, and factor analysis. Probability distribution of muscle activation patterns were compared with the probability distribution of synergy excitation primitives obtained from the four factorisation methods. Muscle synergies extracted using non-negative matrix factorisation best matched the probability distribution of muscle activation patterns across different walking and running speeds. Non-negative matrix factorisation also best tracked changes in muscle activation patterns compared to the other factorisation methods. Our results suggest that non-negative matrix factorisation is the best factorisation method for identifying muscle synergies in dynamic tasks with different levels of muscle contraction.

Comparison of muscle activation imbalance following core stability or general exercises in nonspecific low back pain: a quasi-randomized controlled trial

BackgroundLow back pain causes changes in muscle activation patterns. Knowing how different exercises may improve altered muscle activation is useful in the treatment of patients. The aim of the study was to investigate whether there was a difference in the pattern of muscle activation in chronic nonspecific low back pain sufferers following core stability exercise (CSE) and general exercise (GE).MethodsFifty-six non-specific chronic LBP subjects were randomly assigned to either groups (28 participants in CSE and 28 in GE group). Both groups performed 16 sessions of an exercise program for about 5 weeks. Pain, disability and trunk muscle activation patterns (using surface electromyography) were measured at baseline and post-training.ResultsAfter the intervention period, antagonist coactivation ratio did not change in either groups. Though all compensated imbalance ratios (residual unequal muscular activity after cancellation of directionality) decreased towards negative (imbalance to left side) only this change for total muscles ratio in GE was significant (mean difference in GE group, 0.15; 95% CI: 0.02 to 0.28; p-value of paired t-test: 0.022); (mean difference in CSE, 0.02; 95% CI: − 0.07 to 0.11; p-value of paired t-test: 0.614).. No overall significantly decrease in uncompensated imbalance ratio (absolute imbalance values without cancellation directionality) was observed. Pain and disability decreased significantly in both groups. However, there was no difference between two groups in either of the variables after the intervention.ConclusionsBoth exercise programs reduced pain and disability and made or kept trunk muscle activation imbalance to the left side. The effects of two exercises on pain, disability and antagonist coactivation or imbalance ratios were not different.Trial registrationThis study was registered in the Iranian Clinical Trial Center with the code IRCT201111098035N1, Registered Jan 21, 2013.

Inter-individual variation in hip flexor length may explain differences in trunk flexion during walking in people with knee osteoarthritis

Purpose: Increasing trunk flexion will shift the position of the centre of mass relative to the hip and knee which may lead to changes in muscle activation patterns during walking. Through previous research, we have demonstrated that people with knee osteoarthritis (OA) walk with an increased flexion of the trunk. Our research has also shown that instructing healthy people to increase trunk flexion during walking, by only 5 degrees, produces a distinct increase in duration and magnitude of both the lateral and medial hamstrings. This may indicate that prolonged/increased hamstring activity in people knee OA may, to some degree, result from increased trunk flexion. Importantly, such muscle patterns are known to increase articular load, accelerate the rate of cartilage loss and to be associated with poor long-term clinical outcomes. It is therefore essential that we understand the underlying drivers of altered trunk flexion in people with knee OA. The hip flexor muscle group comprises iliacus, psoas and rectus femoris. As well as functioning to create a hip flexor moment, the relaxed (resting) length of this muscle group could influence the sagittal plane inclination of the pelvis in standing and during movement. Specifically, if the hip flexor muscles are structurally short, this may lead to a relative anterior tilt of the pelvis on the thigh which could, in turn, lead to an increase in trunk flexion. It is therefore possible that the increase in trunk flexion, observed in people with knee OA, is a consequence of short hip flexor muscles. Therefore, this study had two aims. The first was to compare hip flexor length between people with knee OA and healthy control subjects. The second was to understand the association between hip flexor length and trunk inclination during walking, both in healthy people and those with knee OA. Methods: Data was collected from 20 people with radiographically diagnosed OA of the knee and 20 age/BMI matched healthy participants. For each participant, hip flexor length was measured using the Thomas Test. For this test, subjects lay supine with the non-tested leg held against their chest (knee flexed) while the other leg was extended from a flexed position until muscular restriction prevented any further movement. This tested leg hung freely off the edge of the testing plinth while thigh angle, relative to the horizontal, was measured using an inclinometer. Pelvic position was controlled throughout this testing protocol using a pressure biofeedback cuff. An increase in thigh flexion, in the Thomas test, indicates muscular restriction and therefore shortness of the hip flexor muscles, whereas a more extended thigh position, indicates an increased hip flexor length. Measurements were performed on both left and right sides and the average used for subsequent analysis. Following hip flexor testing, kinematic data were collected at a self-selected walking speed. Trunk flexion angles was then calculated, and an average calculated over the period 15-25% of stance as this corresponds to the period of peak knee loading. Independent t-tests were used to compare trunk flexion and hip flexor length between the two groups. A Pearson’s correlational analysis was then used to understand the association between trunk flexion and hip flexor length in each of the two groups separately. Results: Individuals with knee OA demonstrated a more positive Thomas test (p<0.01), mean (SD) = 6.2 (4.2)° compared to the control subjects, mean (SD) = 1.9 (3.7)°, indicating shorter hip flexor muscles in the group with knee OA. The Individuals with knee OA were also observed to walk with 2.8° more trunk flexion (p<0.05). Interestingly, there was a moderate-strong correlation (r=0.67) between hip flexor muscle length and trunk angle during walking in the group with knee OA and a weak-moderate correlation in the healthy group (r=0.45). Conclusions: These data support the idea that people with knee OA exhibit increased muscular restriction of the hip flexor muscle group in static testing and that they walk with more trunk flexion. These data also support the idea that a reduction in the length of the flexor muscles may be a biomechanical driver of increased trunk inclination in people with the disease. Taken together, these findings motivate future research to understand whether interventions that specifically target hip flexor length could lead to reductions in trunk flexion during walking. Such reductions in trunk flexion may lead to changes in hamstring activation patterns and corresponding reductions in the compressive forces at the knee.

Changes in Muscle Activity Patterns and Joint Kinematics During Gait in Hemophilic Arthropathy.

Hemophilic arthropathy is the result of repetitive intra-articular bleeding and synovial inflammation. In people with hemophilic arthropathy (PWHA), very little is known about the neural control of individual muscles during movement. The aim of the present study was to assess if the neural control of individual muscles and coordination between antagonistic muscle pairs and joint kinematics during gait are affected in PWHA. Thirteen control subjects (CG) walked overground at their preferred and slow velocity (1 m/s), and 14 PWHA walked overground at the preferred velocity (1 m/s). Joint kinematics and temporal gait parameters were assessed using four inertial sensors. Surface electromyography (EMG) was collected from gluteus maximus (GMAX), gluteus medius (GMED), vastus medialis (VM), vastus lateralis (VL), rectus femoris (RF), medial gastrocnemius (MG), lateral gastrocnemius (LG), soleus (SOL), tibialis anterior (TA), semitendinosus (ST), and biceps femoris (BF). Waveforms were compared using the time-series analysis through statistical parametric mapping. In PWHA compared to CG, EMG amplitude during the stance phase was higher for LG (for both velocities of the CG), BF (slow velocity only), and ST (preferred velocity only) (p < 0.05). Co-contraction during the stance phase was higher for MG-TA, LG-TA, VL-BF, VM-ST, LG-VL, and MG-VM (both velocities) (p < 0.05). MG and LG were excited earlier (preferred velocity only) (p < 0.05). A later offset during the stance phase was found for VL, BF, and ST (both velocities), and BF and GMAX (preferred velocity only) (p < 0.05). In addition, the range of motion in knee and ankle joints was lower in PWHA (both velocities) and hip joint (preferred velocity only) (p < 0.05). In conclusion, the neural control of individual muscles and coordination between antagonistic muscles during gait in PWHA differs substantially from control subjects.

The effect of a portable electrical muscle stimulation device at home on muscle strength and activation patterns in locomotive syndrome patients: A randomized control trial

The aim of the present study was to quantify the effect of electrical muscle stimulation (EMS) intervention using a portable device on muscle strength and activation patterns in locomotive syndrome. Nineteen women were randomly assigned to the intervention group (n = 10; age = 71–82 years) and control group (n = 9; age = 70–84 years). Participants in the intervention group used a portable EMS device to stimulate the bilateral quadriceps muscles for 8 weeks (23 min/5 days/week). To understand the effects of EMS, the following measurements were made at baseline, 8 weeks, and 12 weeks: locomotive syndrome assessment score, knee extensor strength, vastus lateralis muscle activation patterns during a maximal isometric knee extension contraction using multi-channel surface electromyography, and muscle thickness. The locomotive syndrome assessment, muscle strength, muscle thickness, and muscle activity patterns in the intervention group were significantly different to control after 8 weeks (p < 0.05). However, these results were not sustained at 12 weeks. EMS increased locomotor assessment scores, which were accompanied by enhanced muscle strength, increased muscle thickness, and changes in muscle activation patterns in locomotive syndrome patients. These results suggest that EMS is potentially useful for improving muscle neural activation and force output in locomotive syndrome.

The impact of shoe flexibility on gait, pressure and muscle activity of young children. A systematic review

BackgroundThere is limited evidence of shoe impact in younger children, particularly in the context of immature gait patterns. It is unclear if the impact from shoes in younger children is similar to what has been seen in older children. This systematic review aims to identify any impact of shoe features on younger children’s gait, and if there are any differences between shoe sole flexibility compared to barefoot.MethodsStudy inclusion criteria included: typically developing children aged ≤6 years; comparison of barefoot and shod conditions (walking and/or running) with shoe features or style of shoe described; sample size > 1. Novelty types of footwear were excluded, as was any mention of in shoe support or modifications. Studies were located from six databases. Study methodology was assessed using the McMasters critical review form. Sample size weighted standardized mean differences (SMD) and 95% confidence intervals (CI) were calculated.ResultsFour studies were included. Participant age ranged from 15.2 to 78.7 months, with 262 participants across all studies. All studies had limited methodological bias based on their design type. Compared to barefoot walking, shoes increased velocity, step time and step length. Shod walking decreased cadence. Peak plantar pressure was generally lower in the stiff shoe design and there was a higher peak plantar pressure in the Ultraflex shoes. No studies were found investigating muscle activation.ConclusionsShoes affect younger children’s gait in spatiotemporal gait aspects, similar to those seen in older children. There is limited evidence on effects of particular shoe features such as sole hardness, on gait, and no evidence of any changes in muscle activation patterns. Further research is required to evaluate the impact of different types of shoe and shoe features in this population to provide clinical advice on the type of shoe that is appropriate in this age group.

The influence of knee extensor fatigue on lower extremity muscle activity during chair rise in young and older adults.

The purpose of this investigation was to evaluate alterations in muscular effort and temporal characteristics of their activity during the sit-to-stand (STS) due to isolated fatiguing of the knee extensors, as indicated by declines in torque output. Surface electromyography of the lower extremity was recorded in healthy young (n = 11) and older (n = 11) adults as they ascended from a seated position, before and after dynamic knee extension exercise. Knee extensor fatigue caused significant increases in soleus, gastrocnemius, and gluteus maximus relative effort (%MVC) in both age groups during the STS task. Rectus femoris %MVCs in both young and older adults significantly increased to similar extents throughout the STS movement, whereas vastus lateralis amplitudes only increased in preparation for seat-off. Muscle temporal characteristics appeared to generally be invariant with fatigue, except for earlier activation onset for the ankle musculature in older adult participants. These findings demonstrate that isolated knee extension fatiguing exercise caused compensatory changes in muscle activation patterns and increased reliance of non-fatigued muscles at the ankle and hip as well as increased activity of synergist muscles during the STS. Moreover, this occurred to similar extents in older adults who had lower knee extensor strengths and greater quadriceps %MVCs in comparison to their younger counterparts, regardless of fatigue condition.

Potential Relevance of Altered Muscle Activity and Fatigue in the Development of Performance-Related Musculoskeletal Injuries in High String Musicians.

Muscle fatigue seems to be a risk factor in the development of performance-related musculoskeletal disorders (PRMDs) in musicians, but it is unclear how muscle activity characteristics change between musicians with and without PRMDs over a prolonged playing period. To investigate muscle activity patterns in muscles of the arms, shoulder, and back of high string musicians during prolonged performance. Fifteen professional or university high string musicians were divided into PRMD and non-PRMD groups. All musicians played a chromatic scale, then an individual "heavy" piece for 1 hr, and finally the chromatic scale again. Surface electromyography (sEMG) data were recorded from 16 muscles of the arm, shoulder, and trunk on both sides of the body. Two parameters were analyzed: the percentage load in relation to the respective maximum force during the chromatic scale, and the low-frequency spectrum to determine the fatigue behavior of muscles during the 1-hr play. Changes in muscle activation patterns were observed at the beginning and end of the trial duration; however, these varied depending on whether musicians had PRMDs or no PRMDs. In addition, low-frequency spectrum changes were observed after 1 hr of playing in the PRMD musicians, consistent with signs of muscular fatigue. Differences in muscle activity appear between high string musicians with and without PRMDs as well as altered frequency spectrum shifts, suggesting possible differential muscle fatigue effects between the groups. The applied sEMG analysis proved a suitable tool for detailed analysis of muscle activation characteristics over prolonged playing periods for musicians with and without PRMDs.

Scapholunate interosseous ligament dysfunction as a source of elbow pain syndromes: Possible mechanisms and implications for hand surgeons and therapists

Elbow pain syndromes are common upper extremity musculoskeletal disorders, and they are usually associated with repetitive occupational exposure. Ligaments are often one of the sources of musculoskeletal disorders because of their mechanical and neurological properties. The wrist ligaments are some of the ligaments most vulnerable to occupational exposure. Since most occupational tasks require wrist extension for handling tools and loading, the scapholunate interosseous ligament (SLIL) bears greater strain during loading, which results in creep deformation and hysteresis. Ligamentous creep may result in diminished ability to detect signal changes during joint movements, which impairs neuromuscular control established by ligamentomuscular reflex arcs elicited from mechanoreceptors in the ligaments. Changes in muscle activation patterns of forearm muscles due to diminished ligamentomuscular reflexes may initiate a positive feedback loop, leading to musculoskeletal pain syndromes. The relationship between elbow pain syndromes and SLIL injury will be presented through two hypotheses and relevant pain mechanisms: 1. Repetitive tasks may cause creep deformation of the SLIL, which then impairs ligamentomuscular reflexes, leading to elbow pain disorders. 2. Lateral epicondylalgia may increase the risk of SLIL injury through the compensation of the lower extensor carpi radialis muscle activity by higher extensor carpi ulnaris muscle activity, which may alter carpal kinematics, leading to SLIL degeneration over time. The differential diagnosis is usually complicated in musculoskeletal pain disorders. The failure of treatment methods is one of the issues of concern for many researchers. A key element in developing treatment strategies is to understand the source of the disorder and the nature of the injury. We proposed that the differential diagnosis include SLIL injuries when describing elbow pain syndromes, particularly, lateral epicondylalgia.

A Longitudinal Electromyography Study of Complex Movements in Poststroke Therapy. 1: Heterogeneous Changes Despite Consistent Improvements in Clinical Assessments.

Poststroke weakness on the more-affected side may arise from reduced corticospinal drive, disuse muscle atrophy, spasticity, and abnormal coordination. This study investigated changes in muscle activation patterns to understand therapy-induced improvements in motor-function in chronic stroke compared to clinical assessments and to identify the effect of motor-function level on muscle activation changes. Electromyography (EMG) was recorded from five upper limb muscles on the more-affected side of 24 patients during early and late therapy sessions of an intensive 14-day program of Wii-based Movement Therapy (WMT) and for a subset of 13 patients at 6-month follow-up. Patients were classified according to residual voluntary motor capacity with low, moderate, or high motor-function levels. The area under the curve was calculated from EMG amplitude and movement duration. Clinical assessments of upper limb motor-function pre- and post-therapy included the Wolf Motor Function Test, Fugl-Meyer Assessment and Motor Activity Log Quality of Movement scale. Clinical assessments improved over time (p < 0.01) with an effect of motor-function level (p < 0.001). The pattern of EMG change by late therapy was complex and variable, with differences between patients with low compared to moderate or high motor-function levels. The area under the curve (p = 0.028) and peak amplitude (p = 0.043) during Wii-tennis backhand increased for patients with low motor-function, whereas EMG decreased for patients with moderate and high motor-function levels. The reductions included movement duration during Wii-golf (p = 0.048, moderate; p = 0.026, high) and Wii-tennis backhand (p = 0.046, moderate; p = 0.023, high) and forehand (p = 0.009, high) and the area under the curve during Wii-golf (p = 0.018, moderate) and Wii-baseball (p = 0.036, moderate). For the pooled data over time, there was an effect of motor-function (p = 0.016) and an interaction between time and motor-function (p = 0.009) for Wii-golf movement duration. Wii-baseball movement duration decreased as a function of time (p = 0.022). There was an effect on Wii-tennis forehand duration for time (p = 0.002), an interaction of time and motor-function (p = 0.005) and an effect of motor-function level on the area under the curve (p = 0.034) for Wii-golf. This study demonstrated different patterns of EMG changes according to residual voluntary motor-function levels, despite heterogeneity within each level that was not evident following clinical assessments alone. Thus, rehabilitation efficacy might be underestimated by analyses of pooled data.

Compression apparel does not have an acute effect on quadriceps strength but is associated with changes in muscle activation patterns

BACKGROUND: The mechanism by which increased compression affects muscle strength and electromyographic (EMG) time/frequency domain behavior during prolonged muscle actions has yet to be elucidated. OBJECTIVE: To determine the effectiveness of compression on quadriceps strength and endurance and EMG amplitude/frequency of the quadriceps during repeated concentric muscle contractions. METHODS: Twelve healthy male athletes executed 25 maximal repeated isokinetic knee extensions in compression garment (CG) and control condition (CC) at 60 and 300 ◦ /s on a dynamometer. The EMG time and frequency domain behavior of the rectus femoris (RF), vastus lateralis (VL), and vastus medialis were collected synchronously. RESULTS: Compression exerted no significant effect on peak moment and total work during the isokinetic contractions. By contrast, the overall EMG root mean square amplitude was significantly lower ( p< 0.05) in CG than in CC while the EMG mean power frequency of the RF and VL was significantly higher ( p< 0.05) in CG than in CC at 60 ◦ /s. CONCLUSION: The described effects may potentially improve muscle endurance and fatigue resistance during prolonged muscle actions.

Patterns of Forearm Muscle Activity and Task Parameters Change During a Repetitive Sub-Maximum Forceful Wrist Flexion Task

OCCUPATIONAL APPLICATIONSWhile completing a sub-maximum forceful wrist flexion task for two 1-hour sessions, the temporal patterns of forearm muscle activity of 10 females changed along with corresponding changes in torque, duty-cycle, and torque-time integral. These temporal changes in muscle activity promote variation in muscle activity during repetitive tasks, and as a result may prove to be a protection mechanism for musculoskeletal disorder development. In addition, the changes observed in torque, duty-cycle, or torque-time integral indicate that even during very defined simulated occupational tasks, workers may find ways to interject variation into a task that may also contribute to this protection.TECHNICAL ABSTRACT Background: Jobs requiring repetitive motion are common in many industries, and such jobs can be associated with the development of musculoskeletal disorders. Temporal changes in muscle activity patterns throughout repetitive tasks, if they occur, may promote variation in muscle activity and therefore may prevent the development of musculoskeletal disorders during repetitive work. Purpose: To assess temporal changes in activity patterns of the forearm muscles during a prolonged (2-hour) repetitive wrist flexion task. Methods: Ten females completed a repeated-measures study by performing a task requiring 80° wrist flexions at a rate of 15 flexions per minute overcoming a resistant force set at 25% of their maximum voluntary isometric wrist flexion torque for two 1-hour sessions, with a 5-minute break between the two sessions. Muscle activity of six forearm flexor and extensor muscles was measured using surface electromyography during the first and last 5 minutes of each of the 2-hour sessions. Task performance parameters including torque, cycle time, angle, duty cycle, work, and torque-time integral were also recorded and calculated during the 5-minute periods. Results: Compared to the first 5 minutes of the first hour, mean extensor carpi ulnaris activity was significantly lower during the last 5 minutes of both hours, and the muscle activity percentage of time in gaps was significantly higher for the last 5 minutes of the first hour and both 5-minute periods of the second hour. Torque, duty cycle, and torque-time integral were also significantly lower during the last 5 minutes of the first hour and both 5-minute periods of the second hour compared to the first 5 minutes of the first hour. Conclusions: The observed temporal changes indicate some variation in muscle activity during the repetitive task, which may affect musculoskeletal disorder development. These results provide some preliminary insight into mechanisms that may prevent the development of musculoskeletal disorder development during repetitive tasks.

Effects of spinal cord injury-induced changes in muscle activation on foot drag in a computational rat ankle model.

Spinal cord injury (SCI) can lead to changes in muscle activation patterns and atrophy of affected muscles. Moderate levels of SCI are typically associated with foot drag during the swing phase of locomotion. Foot drag is often used to assess locomotor recovery, but the causes remain unclear. We hypothesized that foot drag results from inappropriate muscle coordination preventing flexion at the stance-to-swing transition. To test this hypothesis and to assess the relative contributions of neural and muscular changes on foot drag, we developed a two-dimensional, one degree of freedom ankle musculoskeletal model with gastrocnemius and tibialis anterior muscles. Anatomical data collected from sham-injured and incomplete SCI (iSCI) female Long-Evans rats as well as physiological data from the literature were used to implement an open-loop muscle dynamics model. Muscle insertion point motion was calculated with imposed ankle trajectories from kinematic analysis of treadmill walking in sham-injured and iSCI animals. Relative gastrocnemius deactivation and tibialis anterior activation onset times were varied within physiologically relevant ranges based on simplified locomotor electromyogram profiles. No-atrophy and moderate muscle atrophy as well as normal and injured muscle activation profiles were also simulated. Positive moments coinciding with the transition from stance to swing phase were defined as foot swing and negative moments as foot drag. Whereas decreases in activation delay caused by delayed gastrocnemius deactivation promote foot drag, all other changes associated with iSCI facilitate foot swing. Our results suggest that even small changes in the ability to precisely deactivate the gastrocnemius could result in foot drag after iSCI.

Medical Equipment to Make Colonoscopy Procedures Safer for Physicians: Control Head Holder and Splatter Shield1

Medical Equipment to Make Colonoscopy Procedures Safer for Physicians: Control Head Holder and Splatter Shield1

Altered postural responses persist following physical therapy of general versus specific trunk exercises in people with low back pain

Interventions that target trunk muscle impairments in people with LBP have been promoted; however, the treatment effects on muscle activation impairments during postural tasks remain unclear. Thus, our objective was to evaluate the effects trunk stabilization vs. general strength and conditioning exercises on the automatic postural response in persons with chronic low back pain (LBP).Fifty-eight subjects with chronic, recurrent LBP (n = 58) (i.e., longer than six months) were recruited and randomly assigned to one of two, 10-week physical therapy programs: stabilization (n = 29) or strength and conditioning (n = 29). Pain and function were measured at 11 weeks and 6 months post-treatment initiation. To quantify postural following support surface perturbations, surface electrodes recorded electromyography (EMG) of trunk and leg muscles and force plates recorded forces under the feet, to calculate the center of pressure.Both groups demonstrated significant improvements in pain and function out to 6 months. There were also changes in muscle activation patterns immediately post-treatment, but not at 6 months. However, changes in center of pressure (COP) responses were treatment specific. Following treatment, the stabilization group demonstrated later onset of COP displacement, while the onset of COP displacement in the strengthening group was significantly earlier following treatment.Despite two different treatments, clinical improvements and muscle activation patterns were similar for both groups, indicating that the stabilization treatment protocol does not preferentially improve treatment outcomes or inter-muscle postural coordination patterns for persons with LBP. Clinical Trial Registration NumberNCT01611792.