Amplitude Of Muscle Activity Research Articles

P 069 - Effects of heel lifts on postural alignment in children with the motor development problem

To investigate if muscle strength and muscle activation patterns are associated with increased knee abduction during two functional tasks, commonly used in rehabilitation for individuals with anterior cruciate ligament reconstruction (ACLR).Cross-sectional study.Laboratory.24 women and 29 men approximately 7 months after ACLR.Isometric peak torque of the trunk and lower extremity muscles were determined during maximal voluntary contractions. Trunk and lower extremity average muscle activation amplitude and peak knee abduction were evaluated during the single-leg squat (SLS) and the single-leg hop for distance (SLHD) for the injured side. Separate backward regressions were performed for men and women.In women, lower knee flexion and extension strength were associated with greater peak knee abduction during the SLS (B = 4.63–18.26, p ≤ 0.036); lower knee flexion strength and iliocostalis activation on the non-injured side were associated with greater peak knee abduction during the SLHD (B = 0.60–20.48, p ≤ 0.043). No associations between muscle function and peak knee abduction were found in men.Muscle function may contribute differently to knee abduction in men and women after ACLR. This should be considered when designing rehabilitation programs to reduce knee abduction in these patients.

Effect of Botulinum Toxin on the Spatial Distribution of Biceps Brachii EMG Activity Using a Grid of Surface Electrodes: A Case Study.

Botulinum toxin (BT) is widely prescribed by physicians for managing spasticity post stroke. In an ongoing study, we examine the spatial pattern of muscle activity in biceps brachii of stroke survivors before and after receiving BT, examined over the course of 11 weeks (2 weeks before - 9 weeks after). We hypothesize that BT alters muscle electrophysiology by disrupting fiber neuromuscular transmission in an inhomogeneous manner and we seek to detect these changes using grid surface electromyography (sEMG). Also, we obtained B-mode ultrasound images to have an accurate interpretation of sEMG data by looking at the fiber angle and subcutaneous fat thickness distribution across muscle. Here, we are reporting a single case where a chronic stroke survivor received BT injection in the biceps brachii (BB). A 16x8 sEMG electrode grid was used to capture the muscle activity distribution of BB during sustained non-fatiguing isometric contraction at 40% of maximal voluntary (MVC) elbow flexion. We obtained the root mean squared (RMS) maps of the signal recorded at each of the $16 \times 8$ electrodes. We observed substantial changes in the RMS pattern of BB muscle after receiving BT. More than 80% decrease in sEMG amplitude (RMS) was observed for the channels around the BT injection site as well as about 74% elbow flexion force reduction at the time point of 3-4 weeks post-injection. We also found significant differences between the spatial voluntary activation pattern of pre and post BT RMS maps. We further observed a non-uniform effect and recovery caused by the BT on the distribution of muscle activity. In conclusion, we observed evidence of alteration of the amplitude and pattern of muscle activity after botulinum toxin injection and can document the capability of grid recordings to detect these pattern changes. Our major goals target further investigation to provide an indepth understanding of the effect of botulinum toxin injection at motor unit level.

The effect of eccentric exercise and delayed onset muscle soreness on the homologous muscle of the contralateral limb

High intensity eccentric exercise induces muscle fiber damage and associated delayed-onset muscle soreness (DOMS) resulting in an impaired ability of the muscle to generate voluntary force. This study investigates the extent to which DOMS, induced by high intensity eccentric exercise, can affect the activation and performance of the non-exercised homologous muscle of the contralateral limb. Healthy volunteers performed maximal voluntary contractions of knee extension and sustained isometric knee extension at 50% of maximal force until task failure on both the ipsilateral exercised limb and the contralateral limb. Surface electromyography (EMG) was recorded from the ipsilateral and contralateral knee extensor muscles (vastus medialis, rectus femoris, and vastus lateralis). Maximal isometric knee extension force (13.7% reduction) and time to task failure (38.1% reduction) of the contralateral non-exercised leg decreased immediately after eccentric exercise, and persisted 24 h and 48 h later (p < 0.05). Moreover, the amplitude of muscle activity recorded from the contralateral knee extensor muscles was significantly lower during the post exercise maximal and submaximal contractions following high intensity eccentric exercise of the opposite limb (p < 0.05). Unilateral high intensity eccentric exercise of the quadriceps can contribute to reduced neuromuscular activity and physical work capacity of the non-exercised homologous muscle in the contralateral limb.

Age-related differences in muscle activity patterns during walking in healthy individuals

ObjectiveTo examine how muscle activity over the entire gait cycle changes with increasing age. MethodsElectromyography data of the erector spinae, rectus femoris, vastus lateralis, biceps femoris, tibialis anterior and gastrocnemius muscles were collected by an instrumented gait analysis during over ground walking in healthy adults aged between 20 and 89 years. Participants were categorized per decade (n = 105, 15 per decade, decades 3–9). Normalized integrated linear envelopes of the electromyographic signal were calculated for one stride. A one way ANOVA using spm1d statistics explored the differences between age groups, followed by a post hoc analysis. ResultsWhile initiation of decline commenced at the age of 60 for erector spinae and tibialis anterior, age-related changes are most pronounced after the age of 80. Concerning timing of muscle activity, subjects in decade 7–9 had prolonged activity and/or early activity of the erector spinae, vastus lateralis, biceps femoris, tibialis anterior and gastrocnemius compared to other decades. Regarding amplitude of muscle activity, decreased peak amplitudes of the erector spinae, rectus femoris, vastus lateralis and gastrocnemius were observed in decades 7–9 compared to other decades. ConclusionBoth timing and amplitude of muscle activation patterns need to be considered to understand the aging process. Regarding the erector spinae, tibialis anterior and vastus lateralis, a decrease in muscle activation coincides with prolonged activity, compared to the gastrocnemius where decreased muscle activation is associated with early activation.

1. Investigating the Link Between Kinematic, Kinetic and Muscular Symmetry in Young Adults 12 or More Months post-ACL Reconstruction

Anterior cruciate ligament (ACL) injury after primary reconstruction and return-to-sport clearance is common. Since research indicates asymmetry as a valid predictor of injury, it is proposed that inter-limb asymmetry following ACL reconstruction contributes to the elevated incidence of re-injury in this population. Current return-to-sport protocol include objective tests such as joint laxity and strength tests, as well as single leg hop and drop landing tests. Since these assessments are based on visual observation, or simple kinematics measurements, it is unclear how visual asymmetry reflects the underlying joint forces and muscular effort responsible for the performance in these tasks. This study aims to assess the asymmetry present at the kinematic, kinetic, and motor control levels to clarify the after-effects of ACL reconstruction. This pilot study will help us appreciate if additional work exploring screening measures as effective tools for predicting ACL injury following primary reconstruction is warranted. Standard techniques will be used to measure the kinematics, joint kinetics and muscle activation during this 25-repetition squat protocol. Correlations will compare the left and right lower limbs for joint angular displacement, joint angular velocity, joint power, vertical ground reaction forces, and muscle activation amplitude.

Mirror Visual Feedback Impact on Abductor Pollicis Brevis Muscle Electrical Activity in the Stroke Affected Arm

Research background and hypothesis. Stroke is recognized as one of the major causes of morbidity, mortality and long-term disability around the world (Laver et al., 2012). Mirror visual feedback is one of the newest areas of research that shows the potential application in neurorehabilitation (Kang et al., 2012). We hypothesize that abductor pollicis brevis muscle activity in the stroke affected arm will be higher when the movements are performed with non-affected hand visual mirror feedback.Research aim was to identify mirror visual feedback impact on abductor pollicis brevis muscle electrical activity in the stroke affected arm.Research methods. Post-stroke subjects (n = 12) performed bimanual thumb opposition under three conditions: without mirror visual feedback, with non-affected and affected arm reflection in the mirror. Electrical activity of abductor pollicis brevis muscle was recorded simultaniously.Research results. There was a significantly higher (p &lt; 0.05) muscle activity amplitude when thumb opposition was performed with visual feedback of non-affected hand compared to task without mirror visual feedback. No muscle activity amplitude difference was observed when thumb opposition was performed looking at affected hand mirror visual feedback compared to task without mirror visual feedback. Motor unit firing rate did not differ between tasks.Discussion and conclusions. I. Nojima and co-authors (2012) have identified that mirror visual feedback activates motor cortex. Additionally, our study shows that even during one-time movement with observation of non-affected hand in the mirror shows higher muscle electrical activity in the affected hand.Keywords: mirror neurones, thumb opposition, bimanual movement.

Electromyographical Gait Characteristics in Parkinson's Disease: Effects of Combined Physical Therapy and Rhythmic Auditory Stimulation.

In persons with Parkinson's disease (PD), gait dysfunctions are often associated with abnormal neuromuscular function. Physical therapy combined with auditory stimulation has been recently shown to improve motor function and gait kinematic patterns; however, the underlying neuromuscular control patterns leading to this improvement have never been identified. (1) Assess the relationships between motor dysfunction and lower limb muscle activity during gait in persons with PD; (2) Quantify the effects of physical therapy with rhythmic auditory stimulation (PT-RAS) on lower limb muscle activity during gait in persons with PD. Participants (15 with PD) completed a 17-week intervention of PT-RAS. Gait was analyzed at baseline, after 5 weeks of supervised treatment (T5), and at a 12-week follow-up (T17). For each session, motor dysfunction was scored using the United Parkinson Disease Rating Scale, and muscle activation amplitude, modulation, variability, and asymmetry were measured for the rectus femoris, tibialis anterior, and gastrocnemius lateralis (GL). Spearman correlation analyses assessed the relationships between dysfunction and muscle activity, and mixed effect models (session × muscle) tested for intervention effects. PT-RAS was effective in decreasing motor dysfunction by an average of 23 (T5) to 36% (T17). Higher GL activity variability and bilateral asymmetry were correlated to higher dysfunction (ρ = 0.301 -0.610, p's < 0.05) and asymmetry significantly decreased during the intervention (p < 0.05). Results suggest that gait motor dysfunction in PD may be explained by neuromuscular control impairments of GL that go beyond simple muscle amplitude change. Physical therapy with RAS improves bilateral symmetry, but its effect on muscle variability requires future investigation.

Muscle activation and sound during voluntary single coughs and cough peals in healthy volunteers: Insights into cough intensity

Very few studies have addressed how coughing varies in intensity. We assessed the influence of cough effort and operating volume on the mechanics of coughing using respiratory muscle surface electromyography (EMG), oesophageal/gastric pressures and cough sounds recorded from 15 healthy subjects [8 female, median age 30 (IQR 30–50)years] performing 120 voluntary coughs from controlled operating volume/effort and three cough peals. For single coughs, low operating volumes and high efforts were associated with the highest EMG activity (p < 0.001); the resultant pressures increased with effort but volume had little influence. In contrast, cough sounds increased with both volume and effort. During cough peals, EMG fell initially, increasing towards the end of peals, pressures remained stable and sound parameters fell steadily to the end of the peal.In conclusion, effort and operating volume have important influences on cough mechanics but modulate muscle activation, pressure and cough sound amplitude and energy differently. Consequently, these cough sound parameters poorly represent voluntary cough mechanics and have limited potential as a surrogate intensity measure.

The involvement of the pathway connecting the substantia nigra, the periaqueductal gray matter and the retrotrapezoid nucleus in breathing control in a rat model of Parkinson's disease

Parkinson's disease (PD) is characterized by a reduction in the number of dopaminergic neurons of the substantia nigra (SNpc), accompanied by motor and non-motor deficiencies such as respiratory failure. Here, our aim was to investigate possible neuronal communications between the SNpc and chemoreceptor neurons within the retrotrapezoid nucleus (RTN), in order to explain neurodegeneration and the loss of breathing function in the 6-OHDA PD animal model. Male Wistar rats received tracer injections in the SNpc, RTN and periaqueductal gray (PAG) regions to investigate the projections between those regions. The results showed that neurons of the SNpc project to the RTN by an indirect pathway that goes through the PAG region. In different groups of rats, reductions in the density of neuronal markers (NeuN) and the number of catecholaminergic varicosities in PAG, as well as reductions in the number of CO2-activated PAG neurons with RTN projections, were observed in a 6-OHDA model of PD. Physiological experiments showed that inhibition of the PAG by bilateral injection of muscimol did not produce resting breathing disturbances but instead reduced genioglossus (GGEMG) and abdominal (AbdEMG) muscle activity amplitude induced by hypercapnia in control rats that were urethane-anesthetized, vagotomized, and artificially ventilated. However, in a model of PD, we found reductions in resting diaphragm muscle activity (DiaEMG) and GGEMG frequencies, as well as in hypercapnia-induced DiaEMG, GGEMG and AbdEMG frequencies and GGEMG and AbdEMG amplitudes. Therefore, we can conclude that there is an indirect pathway between neurons of the SNpc and RTN that goes through the PAG and that there is a defect of this pathway in an animal model of PD.

Gluteal activation and increased frontal plane projection angle during a step-down test in young women

PurposeTo investigate how the activation of gluteus maximus and gluteus medius interacts with different frontal plane projection angles (FPPA) in healthy young women presenting dynamic knee valgus in one limb while performing the step-down test.MethodsThe total of 18 young women presenting FPPA &gt; 15° during the step-down test in one limb (dynamic knee valgus) were assessed. The other limb should present less than 15° for comparisons. The amplitude of muscle activation was assessed through surface electromyography of gluteus medius and gluteus maximus during 8 subsequent weight bearing step-down tests.ResultsFPPA was positively correlated with gluteus maximus activation and with the assessed side showing FPPA &gt; 15°, which also revealed increased activation of gluteus maximus. No differences were noted for gluteus medius. The principal component analysis explained 73% of the variance in 2 components, with gluteus maximus explaining 48% of the variance on the 1st component. Gluteus medius explained 25% on the 2nd component.ConclusionsGluteus maximus seems to be a major component to explain dynamic knee valgus in women without symptoms of patellofemoral pain, probably owing to weakness and lack of stabilization of other proximal muscles of the hip-knee complex during the task.

Contribution of muscle activity at different gait phases for improving walking performance in chronic stroke patients with hemiparesis.

[Purpose] The aim of this study was to clarify the optimal timing for increasing muscle activity in the paralyzed lower limb of stroke survivors by evaluating the relationship between gait muscle activity patterns and gait parameters. [Participants and Methods] Electromyography of the tibialis anterior, soleus, rectus femoris, and biceps femoris on the paralyzed side and spatiotemporal gait parameters were evaluated in 40 chronic post-stroke patients as they walked at a comfortable speed. The normalized average amplitude and asymmetry indexes of each gait phase were calculated. The correlations between gait velocity or asymmetry indexes and the activity amplitudes of various muscles during each gait phase were analyzed. Multiple regression analysis was performed with gait velocity or asymmetry indexes as the response variable and the muscle activity amplitudes in the various gait phases as explanatory variables. [Results] The major determinants of gait velocity were the tibialis anterior activity (β=−0.35) and biceps femoris activity (β=0.45) during the swing phase. In addition, the biceps femoris activity during the swing phase was the major determinant of the asymmetry index for the swing phase duration (β=−0.41). [Conclusion] For patients with hemiparesis, increasing the biceps femoris activity during the swing phase is considered optimal, which may lead to improvement in walking performance.

Observations on muscle activity in REM sleep behavior disorder assessed with a semi-automated scoring algorithm

ObjectivesRapid eye movement (REM) sleep behavior disorder (RBD) is defined by dream enactment due to a failure of normal muscle atonia. Visual assessment of this muscle activity is time consuming and rater-dependent. MethodsAn EMG computer algorithm for scoring ‘tonic’, ‘phasic’ and ‘any’ submental muscle activity during REM sleep was evaluated compared with human visual ratings. Subsequently, 52 subjects were analyzed with the algorithm. Duration and maximal amplitude of muscle activity, and self-awareness of RBD symptoms were assessed. ResultsThe computer algorithm showed high congruency with human ratings and all subjects with RBD were correctly identified by excess of submental muscle activity, when artifacts were removed before analysis. Subjects with RBD exhibited prolonged bouts of ‘phasic’ muscle activity with high amplitude. Self-awareness of RBD symptoms correlated with amount of REM sleep without atonia. ConclusionsOur proposed algorithm was able to detect and rate REM sleep without atonia allowing identification of RBD. Increased duration and amplitude of muscle activity bouts were characteristics of RBD. Quantification of REM sleep without atonia represents a marker of RBD severity. SignificanceOur EMG computer algorithm can support a diagnosis of RBD while the quantification of altered muscle activity provides a measure of its severity.

Active and passive contributions to arm swing: Implications of the restriction of pelvis motion during human locomotion

Current research has yet to determine how passive dynamics and active neural control contribute to upper limb swing during human locomotion. The present study aimed to investigate these contributions by restricting pelvis motion during walking, thereby altering the upward energy transfer from the swinging lower limbs. Ten healthy individuals walked freely on a treadmill (CON) and with an apparatus that reduced pelvis motion (PR) at three walking speeds (0.9, 1.3, and 1.8m/s). Spatiotemporal characteristics of limb movement and muscle activation were recorded and analyzed. When wearing the apparatus, the ranges of the sagittal and transverse rotations of the trunk and shoulders, as well as vertical trunk center of mass movement all decreased. At higher treadmill speeds, the movement amplitudes of the upper and lower limbs increased. This increase was less pronounced in the upper limbs when the apparatus reduced pelvis motion. However, this decrease in arm swing was accompanied with a preservation of upper and lower limb muscle activity amplitudes. The temporal coordination between upper and lower limbs was also conserved irrespective of the PR or CON conditions. Relating shoulder muscle activities to upper limb kinematics suggested these muscles mainly acted eccentrically, providing evidence that passive elements are a significant factor in arm swing control. However, the conserved muscle activity patterns and temporal coupling of limb movements when pelvis motion was reduced are suggestive of an underlying active maintenance of the locomotor pattern via linked upper and lower limb neural networks.

Electromiography comparison of distal and proximal lower limb muscle activity patterns during external perturbation in subjects with and without functional ankle instability

Ankle sprain is one of the most common injuries among athletes and the general population. Most ankle injuries commonly affect the lateral ligament complex. Changes in postural sway and hip abductor muscle strength may be generated after inversion ankle sprain. Therefore, the consequences of ankle injury may affect proximal structures of the lower limb. The aim is to describe and compare the activity patterns of distal and proximal lower limb muscles following external perturbation in individuals with and without functional ankle instability. The sample consisted of 16 women with functional ankle instability and 18 healthy women were recruited to participate in this research. The external perturbation via body jacket using surface electromyography, amplitude and onset of muscle activity of gluteus maximums, gluteus medius, tibialis anterior, and peroneus longus was recorded and analyzed during external perturbation. There were differences between the onset of muscles activity due to perturbation direction in the two groups (healthy and functional ankle instability). In the healthy group, there were statistically significant differences in amplitude of proximal muscle activity with distal muscle activity during front perturbation with eyes open and closed. In the functional ankle instability group; there were statistically significant differences in amplitude of proximal muscle activity with distal muscle activity during perturbation of the front and back with eyes open. There were statistically significant differences in the onset of muscle activity and amplitude of muscle activity, with-in and between groups (P<0.05). Therefore, in the presence of functional ankle instability, activation patterns of the lower limb proximal muscles may be altered.

Chronic pain alters spatiotemporal activation patterns of forearm muscle synergies during the development of grip force.

It is largely unknown how the CNS regulates multiple muscle systems in the presence of pain. This study used muscle synergy analysis to investigate multiple forearm muscles in individuals with chronic elbow pain during the development of grip force. Eleven individuals with chronic elbow pain and 11 healthy age-matched control subjects developed grip force to 15% and 30% of maximum voluntary contraction (MVC). Surface electromyography was obtained from six forearm muscles during force development before nonnegative matrix factorization was performed. The relationship between muscle synergies and standard clinical tests of elbow pain were examined by linear regression. During grip force development to 15% MVC the pain group had a lower number of forearm muscle synergies, increased similarity in spatial activation patterns, increased cocontraction of forearm flexors, and a greater magnitude of muscle weightings across the forearm when performing the task. During the 30% MVC grip the numbers of muscle synergies were the same for both groups; however, the pain group had lower activation and reduced variability in the timing of peak activation. The timing of peak activation was delayed in the pain group regardless of the task, and performing the grip in different wrist postures did not affect muscle synergy characteristics in either group. Although localized pain causes direct dysfunction of an affected muscle, this study provides evidence that the timing and amplitude of agonist and antagonist muscle activity are also affected with chronic pain.NEW & NOTEWORTHY Muscle activation patterns of individuals with chronic elbow pain are simplified compared with healthy individuals. This is apparent as individuals with pain exhibit fewer forearm muscle synergies, and increased similarity of activation patterns between forearm muscles, when performing pain-free isometric gripping. As such, even during pain-free tasks it is possible to observe changes in motor control in people with chronic pain.

Compensating for intersegmental dynamics across the shoulder, elbow, and wrist joints during feedforward and feedback control

Moving the arm is complicated by mechanical interactions that arise between limb segments. Such intersegmental dynamics cause torques applied at one joint to produce movement at multiple joints, and in turn, the only way to create single joint movement is by applying torques at multiple joints. We investigated whether the nervous system accounts for intersegmental limb dynamics across the shoulder, elbow, and wrist joints during self-initiated planar reaching and when countering external mechanical perturbations. Our first experiment tested whether the timing and amplitude of shoulder muscle activity account for interaction torques produced during single-joint elbow movements from different elbow initial orientations and over a range of movement speeds. We found that shoulder muscle activity reliably preceded movement onset and elbow agonist activity, and was scaled to compensate for the magnitude of interaction torques arising because of forearm rotation. Our second experiment tested whether elbow muscles compensate for interaction torques introduced by single-joint wrist movements. We found that elbow muscle activity preceded movement onset and wrist agonist muscle activity, and thus the nervous system predicted interaction torques arising because of hand rotation. Our third and fourth experiments tested whether shoulder muscles compensate for interaction torques introduced by different hand orientations during self-initiated elbow movements and to counter mechanical perturbations that caused pure elbow motion. We found that the nervous system predicted the amplitude and direction of interaction torques, appropriately scaling the amplitude of shoulder muscle activity during self-initiated elbow movements and rapid feedback control. Taken together, our results demonstrate that the nervous system robustly accounts for intersegmental dynamics and that the process is similar across the proximal to distal musculature of the arm as well as between feedforward (i.e., self-initiated) and feedback (i.e., reflexive) control.NEW & NOTEWORTHY Intersegmental dynamics complicate the mapping between applied joint torques and the resulting joint motions. We provide evidence that the nervous system robustly predicts these intersegmental limb dynamics across the shoulder, elbow, and wrist joints during reaching and when countering external perturbations.

Evaluation of a laser-based sensor for the diagnosis of neurological disorders.

Involuntary muscle activities like fasciculations or tremor are an indication for several neurological disorders. However, currently used techniques for measuring those activities are limited due to their invasiveness, the unsuitability for measuring a whole body simultaneously and the lack of an objective measurement of amplitude and duration of muscle activity. Hence, we developed a new laser-based sensor for the remote quantification of muscle activity. In the present paper we show a basic evaluation of our system by reference to ultrasound measurements. Our results show the detection limits of our remote sensor technology in terms of fasciculation size and depth within the muscle. Those results will help us for a better interpretation of our measurement results and hold promise for the future development of our system.

Effects of Foot Orthoses Extrinsic Rearfoot and Forefoot Posts on Muscle Activity During Walking: A Case Study

ABSTRACT Introduction In clinical practice, different types of rearfoot and forefoot extrinsic posts are regularly added to foot orthoses (FOs) to make the treatment more specific. However, to this day, their effects on muscle activity during walking are still unclear and few studies have quantified them. The purpose of this case study was to quantify the effects of FOs with different extrinsic rearfoot and forefoot posts on muscle activity during walking to generate hypotheses with the goal to develop a more complex experimental design for further studies. Materials and Methods A 26-year-old man with hyperpronated feet was recruited to walk on a 5-meter walkway with seven pairs of FOs with different extrinsic rearfoot and forefoot posts (no post, external oblique rearfoot post, internal oblique rearfoot post, straight rearfoot post, rearfoot and forefoot posts, rearfoot and forefoot posts at 2° varus, and rearfoot and forefoot posts at 5° varus). Mean activity of eight lower-limb muscles (gluteus medius, vastus lateralis, vastus medialis, biceps femoris, medial gastrocnemius, lateral gastrocnemius, fibularis longus, and tibialis anterior) was analyzed during the three phases of the walking cycle (contact, midstance, and propulsion). Peak root mean square (RMS) amplitude was also measured. Results Significant differences were observed between the control and the experimental conditions for mean muscle activity and peak RMS amplitude during the gait cycle. Results were variable between conditions. However, in general, more muscle activity was observed when increasing the frontal plane inclination of the extrinsic rearfoot and forefoot posts. Conclusions The addition of extrinsic rearfoot and forefoot posts to the FOs can modulate muscle function during walking. However, to this day, not enough data are available to build a clinical guideline, and it is still unknown if they can have positive effects on musculoskeletal pathologies of the lower limb.

Activation of the semispinalis cervicis and splenius capitis with cervical pulley exercises

Study designQuasi-Experimental. ObjectiveTo assess the activation of semispinalis cervicis (d-SSC) and splenius capitis (s-SC) muscles, and the activation between the two during neck pulley and free weight exercises. BackgroundAltered activation of cervical extensors may occur with neck pain, suggesting that exercises should be designed to target these muscles. Methodsd-SSC and s-SC activity was recorded unilaterally with intramuscular electromyography from healthy volunteers during cervical isometric exercises: 1) extension with a pulley rope angled from incline to vertical, 2) extension with right, left and central forehead hanging weight, and 3) rotation with pulley rope angled from incline to decline. ResultsExtension against a vertical force led to greater activation of d-SSC (P < 0.001) and s-SC (P < 0.001) compared to the inclined, declined and horizontal pulley. With each of these conditions, amplitude of muscle activity was higher for the d-SSC compared to the s-SC muscle (P < 0.0001). Extension with free weight hanging on right, left or central forehead, showed no differences across conditions, although in each condition, the d-SSC amplitude was higher than the s-SC. For cervical rotation, the declined pulley led to the greatest activation of both muscles (P < 0.05). Higher levels of activity were observed for the s-SC compared to the d-SSC (P < 0.01) for all rotation conditions. ConclusionA vertical resistance during an extension exercise or a declined resistance during cervical rotation, increased neck extensor activation. The results from this preliminary study provide guidance for future work on the exploration and development of low-load exercise design for patients with neck pain disorders.

Dual-belt treadmill familiarization: Implications for knee function in moderate knee osteoarthritis compared to asymptomatic controls

BackgroundEffect of treadmill familiarization on knee function in osteoarthritis is not clear. Purpose was to determine whether spatiotemporal characteristics, knee joint biomechanics and muscle activation patterns change as individuals with and without medial compartment knee osteoarthritis familiarize to dual-belt treadmill walking over 6min. Methods20 individuals with knee osteoarthritis and 20 asymptomatic controls walked at a self-selected speed. Spatiotemporal characteristics, sagittal plane joint motions, sagittal and frontal plane moments and knee joint muscle activation patterns, amplitude normalized to maximum isometric contractions were analyzed. Discrete measures were extracted from each biomechanical waveform and principal component analysis was used to determine knee joint muscle activation patterns. Statistical significance was determined using Analysis of Variance models (alpha=0.05). FindingsSpatiotemporal gait characteristics, knee motion and moment differences were found between groups however no group by time interactions existed and no changes in these variables were found over 6min of walking. Group differences in muscle activation patterns were found in all muscle activations. Muscle activation amplitude and patterns at minute 5 and 6 were generally lower, less prolonged and more dynamic when compared to minute 1 and 3. InterpretationIndividuals with and without medial compartment knee osteoarthritis familiarized to treadmill walking in a similar manner. Minimal changes to knee biomechanics were found during treadmill familiarization. Five to six minutes of familiarization should be considered for surface electromyography in these populations.