Co-contraction Ratio Research Articles

Hamstring Co-Contraction in the Early Stage of Rehabilitation After Anterior Cruciate Ligament Reconstruction: A Longitudinal Study.

Hamstring co-contraction may affect recovery from anterior cruciate ligament reconstruction. The aim of the study was to evaluate the changes in hamstring co-contraction during the early postoperative stages. Twenty-five patients with anterior cruciate ligament reconstruction were followed up for 1-3 mos postoperatively, during which the Lysholm and International Knee Documentation Committee questionnaires were completed and surface electromyograms were assessed during terminal knee extension maximum voluntary contraction and step-up tests. The integrated electromyogram of the tested muscles and co-contraction ratio were analyzed. Co-contraction ratio during terminal knee extension maximum voluntary contraction at 3 mos postoperatively was significantly less than that at 1 mo postoperatively (P < 0.0083), and it did not significantly differ from that of the uninvolved knee. In contrast, the co-contraction ratio during step-up was significantly higher at 2 and 3 mos postoperatively than that before surgery (P < 0.0167) and for the uninvolved knee (P < 0.05). Moreover, the postoperative hamstring co-contraction ratio in patients with a chronic injury was significantly higher during the step-up test than in patients with an early injury (P = 0.017). Hamstring co-contraction ratio during terminal knee extension maximum voluntary contraction recovers during the early postoperative stages. However, hamstring co-contraction ratio during step-up, which may be related to knee joint proprioception, remains high, particularly for patients with a chronic injury. ChiCTR-COC-17011167.

The Impact of Music and Attentional Focus on Muscular Activation

Neuromuscular efficiency is improved during exercise when attention is focused externally on the effects of movement, rather than internally on the generation of movement. Music is a form of external attentional focus which may yield additional psychological benefits during exercise. The impact of music on neuromuscular efficiency remains to be fully investigated. PURPOSE: To determine the effects of music and other attentional focus conditions on muscular activation and psychological response to single-joint isometric exercise. METHODS: Apparently healthy subjects (N = 23; 12 men) completed an isometric elbow flexion task (40% of predetermined 3RM) for 1 min in three randomized, counterbalanced conditions: internal focus (INT), external focus with a simple distraction task (EXT), and external focus listening to music (MUS). Muscle activation of the biceps (BI) and triceps (TRI) brachii were recorded at 15 s intervals using a 4 channel Delsys EMG system, and were used to compute cocontraction ratio (CCN). Heart rate (HR) was measured throughout the exercise tasks and recorded at 15 s intervals. Psychological characteristics of perceived exertion (RPE), affective valence, task-motivation, and attentional focus were measured at the end of each trial using single-item scales. Repeated measures 3 (condition) x 4 (time) ANOVAs were used to analyze the physiological variables (BI, TRI, CCN, and HR). Psychological variables were compared across conditions using a series of one-way repeated measures ANOVAs. RESULTS: No significant interaction effect or main effect for condition was found for any of the physiological variables (p > .05), though there was a trend (p = .071, η2 = .12) for decreased HR with MUS (91.41 bpm) compared to INT (93.87 bpm). There was a significant main effect of condition on RPE (p = .002, η2 = .25), with a greater RPE in INT (13.87) compared to EXT (12.39) and MUS (12.61). CONCLUSIONS: The primary finding from the current study was that external focus, through both music and a distraction task, reduced the perception of effort during brief single-joint isometric exercise, despite the fact that muscle activation and physiological demand were unchanged.

Determination of Optimal Riding Positions using Muscle Co-Contraction on Upper Extremity during Manual Standing Wheelchair Propulsion

A newly designed standing wheelchair that moves even while standing posture has been developed to improve the health and the quality of life for wheelchair users. However, this standing wheelchair has hand rims separate from the wheels, likely affecting the biomechanical characteristics and the efficiency of propulsion. Thus, this study aimed to propose a method to determine the optimal riding position by evaluating muscle activation during manual standing wheelchair propulsion. Ten elderly male subjects were asked to propel the hand rims with nine different seat (while sitting) and footrest (while standing) positions. During the experiments, kinematic data were obtained using a 3D motion capture system and sEMG measurement system, respectively. Simultaneously, surface electromyography signals were recorded from eleven muscles on the right side of the trunk and the upper extremity to evaluate relative iEMG and muscle co-contraction ratio. The muscle co-contraction ratio was higher at positions (upward and backward directions) distant from the hand rim and lower at positions (downward and forward directions) close to the hand rim. These results indicate that decreased distance from the hand rim enhances joint stability and decreases muscle co-contraction. These results also showed a good similarity with our previous study using energy expenditure method.

Impact of Targeted Assistance of Multiarticular Finger Musculotendons on the Coordination of Finger Muscles During Isometric Force Production.

Neurological injuries often cause degraded motor control. While rehabilitation efforts typically focus on movement kinematics, abnormal muscle activation patterns are often the primary source of impairment. Muscle-based therapies are likely more effective than joint-based therapy. In this paper, we examined the feasibility of biomimetic input mimicking the action of human musculotendons in altering hand muscle coordination. Twelve healthy subjects produced a submaximal isometric dorsal fingertip force, while a custom actuator provided assistance mirroring the actions of either the extrinsic extensor or the intrinsic muscles of the index finger. The biomimetic inputs reduced the activation level of all task-related muscles, but the degree of change was different across the muscles, resulting in significant changes in their coordination (co-contraction ratios) and force-electromyography correlations. Each biomimetic assistance particularly increased the neural coupling between its targeted muscle and the antagonist muscle. Subjects appeared to fully take advantage of the assistance, as they provided minimal level of effort to achieve the task goal. The targeted biomimetic assistance may be used to retrain activation patterns post-stroke by effectively modulating connectivity between the muscles in the functional context and could be beneficial to restore hand function and reduce disability.

Co-contraction characteristics of lumbar muscles in patients with lumbar disc herniation during different types of movement

BackgroundMuscular performance is an important factor for the mechanical stability of lumbar spine in humans, in which, the co-contraction of lumbar muscles plays a key role. We hypothesized that when executing different daily living motions, the performance of the lumbar muscle co-contraction stabilization mechanism varies between patients with lumbar disc herniation (LDH) and healthy controls. Hence, in this study, co-contraction performance of lumbar muscles between patients with LDH and healthy subjects was explored to check if there are significant differences between the two groups when performing four representative movements.MethodsTwenty-six LDH patients (15 females, 11 males) and a control group of twenty-eight subjects (16 females, 12 males) were recruited. Surface electromyography (EMG) signals were recorded from the external oblique, lumbar multifidus, and internal oblique/transversus abdominis muscles during the execution of four types of movement, namely: forward bending, backward bending, left lateral flexion and right lateral flexion. The acquired EMG signals were segmented, and wavelet decomposition was performed followed by reconstruction of the low-frequency components of the signal. Then, the reconstructed signals were used for further analysis. Co-contraction ratio was employed to assess muscle coordination and compare it between the LDH patients and healthy controls. The corresponding signals of the subjects in the two groups were compared to evaluate the differences in agonistic and antagonistic muscle performance during the different motions. Also, sample entropy was applied to evaluate complexity changes in lumbar muscle recruitment during the movements.ResultsSignificant differences between the LDH and control groups were found in the studied situations (p < 0.05). During the four movements considered in this study, the participants of the LDH group exhibited a higher level of co-contraction ratio, lower agonistic, and higher antagonistic lumbar muscle activity (p < 0.01) than those of the control group. Furthermore, the co-contraction ratio of LDH patients was dominated by the antagonistic muscle activity during the movements, except for the forward bending motion. However, in the healthy control group, the agonistic muscle activity contributed more to the co-contraction ratio with an exception for the backward bending motion. Conversely, the sample entropy value was significantly lower for agonistic muscles of LDH group compared to the control group (p < 0.01) while the entropy value was significantly greater in antagonistic muscles (p < 0.01) during the four types of movement, respectively.ConclusionsLumbar disc herniation patients exhibited numerous variations in the evaluated parameters that reflect the co-contraction of lumbar muscles, the agonistic and antagonistic muscle activities, and their respective sample entropy values when compared with the healthy control group. These variations could be due to the compensation mechanism that was required to stabilize the spine. The results of this study could facilitate the design of efficient rehabilitation methods for treatment of lumbar muscle dysfunctions.

Repeated magnetic stimulation improves the effectiveness of exercise therapy in relieving ankle spasticity after stroke

Objective To study the effect of repetitive peripheral magnetic stimulation combined with exercise on spasticity in the ankle plantar flexors among stroke survivors. Methods Sixty stroke survivors with spasticity in their ankle plantar flexors were randomly divided into a treatment group and a control group, each of 30. Both groups were given conventional kinesitherapy, while the treatment group were additionally provided with repetitive peripheral magnetic stimulation for 4 weeks. The myoelectric activity of the agonist and antagonist muscles was recorded using surface electromyography during maximum isometric voluntary contractions of the ankle dorsiflexors and co-contraction ratios (CRs) were calculated. The motor function, walking ability and ankle plantar flexor spasticity were evaluated using the Fugl-Meyer lower extremity assessment (FMA-LE), functional ambulation categories (FACs) and a composite spasticity scale (CSS). Results Before the intervention there was no signification difference between the two groups in terms of any of the assessments. After 4 weeks of treatment, the average integrated EMG of the anterior tibialis in the treatment group was significantly better than in the control group. That group′s average FMA-LE and FAC scores were also significantly better. The experimental group′s average spasticity score and co-contraction ratio during maximum isometric voluntary contractions of the ankle dorsiflexors had both decreased significantly. All of the improvements in the treatment group were significantly better than those in the control group. Conclusion Repetitive peripheral magnetic stimulation combined with the exercise therapy can effectively reduce ankle plantar flexior spasticity while improving motor function and walking ability. It is more effective than exercise alone. Key words: Magnetic stimulation; Exercise therapy; Stroke; Spasticity; Surface electromyography

Does chronic ankle instability influence lower extremity muscle activation of females during landing?

Much remains unclear about how chronic ankle instability (CAI) could affect knee muscle activations and interact with knee biomechanics. Therefore, the purpose of this study was to assess the influence of CAI on the lower extremity muscle activation at the ankle and knee joints during landings on a tilted surface. A surface electromyography system and two force plates were used to collect lower extremity muscle activation of 21 young female individuals with CAI and 21 pair-matched controls during a double-leg landing with test limb landing on the tilted surface. In the pre-landing phase, compared to controls, CAI participants displayed a reduced ankle evertor activation that could place CAI at a high risk of giving way or sprain injury. In the landing phase, an increased tibialis anterior activation of CAI led to increased co-contraction of ankle muscles in the sagittal and frontal plane. A greater ankle muscle co-contraction could increase the ankle stability during landings but may adversely influence the knee muscle activations (e.g., a greater co-contraction ratio of quadriceps to hamstrings). Relevant training programs (e.g., increasing pre-landing peroneal activation, and optimizing activation ratio of quadriceps to hamstrings) may help individuals with CAI improving ankle stability and reduce atypical knee loading during landings.

Neuromuscular compensatory strategies at the trunk and lower limb are not resolved following an ACL reconstruction

BackgroundFollowing anterior cruciate ligament reconstruction (ACLR), patients present with greater trunk ipsilateral lean, which may affect knee kinetics and increase re-injury risk. However, there has been little research into neuromuscular factors controlling the trunk and their relation to the knee between healthy and ACLR subjects. This is critical to establish in order to develop more directed and effective interventions. HypothesisAs compared to healthy control subjects, ACLR subjects will demonstrate increased erector spinae and rectus abdominis co-contraction, greater rectus abdominis force and greater hamstring force that is correlated to increased forward trunk lean. Study designCross-sectional study, Level of Evidence: 3. MethodsEleven healthy and eleven ACLR subjects were matched for age, mass and height. Subjects were asked to run at a self-selected speed while instrumented gait analysis was performed. An anthropometrically scaled OpenSim model was created for each subject. Trunk and hamstring muscle forces from Static Optimization were analyzed at impact peak. Additionally, directed co-contraction ratios were calculated for the erector spinae and erector spinae/rectus abdominis combinations. ResultsACLR subjects showed more balanced erector spinae co-contraction [p<0.01], and greater hamstring force [biceps femoris long head (p=0.02), semimembranosus (0.01), semitendinosus (0.01)]. There was no statistical difference for any other muscle group. ConclusionDespite release to return to sport, ACLR subjects are continuing to increase the stiffness of their trunk as well increase their hamstring force to potentially reduce anterior tibial translation. Clinical relevanceClinicians may anticipate ACLR subjects using their erector spinae and hamstrings to maintain a sense of stability in their trunk and at their knee.

O-2-6-15. Immediate effects of anodal tDCS combined with patterned electrical stimulation on gait performance in patients with stroke

Anodal transcranial direct current stimulation (tDCS) combined with patterned electrical stimulation (PES) modulates spinal reciprocal inhibition and improves the ankle movement in patients with incomplete spinal cord injury (Yamaguchi et al., 2016). This study aimed to examine the immediate effects of anodal tDCS combined with PES on gait performance in patients with stroke. Twelve patients with subacute stroke participated in this double-masked, sham-controlled cross-over study. They randomly participated in the following sessions on separate days: (1) anodal tDCS + PES; (2) anodal tDCS + sham PES; (3) sham tDCS + PES. The gait speed and surface electromyography (EMG) of tibialis anterior (TA) and soleus (SOL) muscles were measured before and after the intervention. As a result, the gait speed was not changed before and after the stimulation in all interventions. In anodal tDCS + PES condition, the EMG of the TA after the stimulation was significantly greater than that in the swing phase compared with other interventions. Anodal tDCS + PES produced significant improvement in the co-contraction ratio between TA and SOL after the stimulation, while other interventions produced no change. These findings suggest that anodal tDCS + PES could improve walking function in patients with stroke.

Isokinetic angle-specific moments and ratios characterizing hamstring and quadriceps strength in anterior cruciate ligament deficient knees

This study is intended to find more effective and robust clinical diagnostic indices to characterize muscle strength and coordination alternation following anterior cruciate ligament (ACL) rupture. To evaluate angle-specific moments and hamstring (H)/quadriceps (Q) ratios, 46 male subjects with unilateral chronic ACL-rupture performed isokinetic concentric (c), eccentric (e) quadriceps and hamstring muscle tests respectively at 60°/s. Normalized moments and H/Q ratios were calculated for peak moment (PM) and 30°, 40°, 50°, 60°, 70°, 80° knee flexion angles. Furthermore, we introduced single-to-arithmetic-mean (SAM) and single-to-root-mean-square (SRMS) muscle co-contraction ratios, calculating them for specific angles and different contraction repetitions. Normalized PM and 40° specific concentric quadriceps, concentric hamstring strength in the ACL-deficient knee were reduced significantly (P ≤ 0.05). Concentric angle-specific moments together with Qe/Qc ratios at 40° (d = 0.766 vs. d = 0.654) identify more obvious differences than peak values in ACL ruptured limbs. Furthermore, we found SRMS-QeQc deficits at 40° showed stronger effect than Qe/Qc ratios (d = 0.918 vs. d = 0.766), albeit other ratio differences remained basically the same effect size as the original H/Q ratios. All the newly defined SAM and SRMS indices could decrease variance. Overall, 40° knee moments and SAM/SRMS ratios might be new potential diagnosis indices for ACL rupture detection.

Contribution of upper limb muscles to two different gripping styles in elite indoor tug of war athletes

To investigate characteristic upper limb muscle use between two common tug of war (TOW) gripping styles, 20 elite athletes from two high school TOW teams were recruited. Under conditioned attack pulling (with 90% maximal force) on a tug machine, participants used their own habitual gripping style to pull for five 15-s trials. Force and kinematic measurements showed a significantly better force performance and higher centre-of-gravity tilting angle with the gripping style one than with the gripping style two (GS2) (both p < 0.05). However, an overall higher and more symmetrical muscle activation detected by normalised surface electromyography signal amplitude was found in the GS2 group (both p < 0.05). In both groups, the distal and flexor muscles were more activated than the proximal and extensor muscles, respectively (p < 0.05). Higher co-contraction ratio was found in the wrist joints of the latter arm in both groups (p < 0.05). As higher muscle activation level and co-contraction indicate higher muscle and joint injury incidences, we suggest that gripping style factors should be considered in training to prevent muscle and joint injury. Future study concerning segmental kinematics, ground reaction force, moment arm and muscle endurance during the defence phase are warranted.

Surface electromyographic examination of the coordination of the spastic upper limb muscles of stroke survivors

Objective To explore any changes in the surface electromyography (sEMG) signals measured on the spastic upper limb muscles of stroke parents during maximum isometric voluntary contraction and to analyze any abnormal synergy patterns quantitatively in order to design better rehabilitation programs for developing coordination. Methods Ten stroke survivors with hemiparesis were selected into a patient group and ten healthy counterparts were recruited into a control group. sEMG signals were recorded bilaterally from the flexor carpi ulnaris (FCU), biceps brachii (BB), triceps brachii (TB) and deltoid (D) during maximum isometric voluntary contractions involving wrist flexion and extension, elbow flexion and extension, and shoulder abduction. The two groups′ co-contraction ratios (CR) and co-activation ratios were calculated and compared. Results During elbow flexion and extension the average CR of the BB on the affected side was significantly higher than that on the unaffected side and also significantly higher than the control group average. The average CR of the TB on the affected side was significantly higher than that of the healthy controls. In all cases the average CR of the BB was larger than that of the TB. The difference in CR between the TB and the BB on the affected side was significantly larger than on the unaffected side and the control group average. During elbow flexion, the co-activation ratio of the FCU, TB and D on the affected side was significantly higher than on the unaffected side and among the healthy controls, and the co-activation ratio of the FCU on the affected side was significantly higher than that of the D and TB. During elbow extension, the co-activation ratio of the FCU, BB and D on the affected side was significantly higher in the same way, and the co-activation ratio of the FCU on the affected side was again significantly higher than that of the D and BB. During wrist flexion, the average co-activation ratio of the BB and D on the affected side was significantly greater than that on the unaffected side and among the healthy controls, and the co-activation ratio of the BB on the affected side was significantly higher than that of the D and TB. During shoulder abduction, the co-activation ratio of the BB on the affected side was significantly larger than on the unaffected side and among the healthy controls. Conclusion After a stroke the upper limbs often show flexor spasticity and abnormal synergy patterns. Rehabilitation strategy should be adopted to tackle these so as to enhance overall limb coordination. Key words: Stroke; Spasticity; Surface electromyography; Muscle coordination; Abnormal synergy

The influence of digital filter type, amplitude normalisation method, and co-contraction algorithm on clinically relevant surface electromyography data during clinical movement assessments

There is a large and growing body of surface electromyography (sEMG) research using laboratory-specific signal processing procedures (i.e., digital filter type and amplitude normalisation protocols) and data analyses methods (i.e., co-contraction algorithms) to acquire practically meaningful information from these data. As a result, the ability to compare sEMG results between studies is, and continues to be challenging. The aim of this study was to determine if digital filter type, amplitude normalisation method, and co-contraction algorithm could influence the practical or clinical interpretation of processed sEMG data. Sixteen elite female athletes were recruited. During data collection, sEMG data was recorded from nine lower limb muscles while completing a series of calibration and clinical movement assessment trials (running and sidestepping). Three analyses were conducted: (1) signal processing with two different digital filter types (Butterworth or critically damped), (2) three amplitude normalisation methods, and (3) three co-contraction ratio algorithms. Results showed the choice of digital filter did not influence the clinical interpretation of sEMG; however, choice of amplitude normalisation method and co-contraction algorithm did influence the clinical interpretation of the running and sidestepping task. Care is recommended when choosing amplitude normalisation method and co-contraction algorithms if researchers/clinicians are interested in comparing sEMG data between studies.

Functional electrical stimulation and weight loss treadmill synchronous training after botulinum toxin injection can relieve foot-drop and strephenopodia among stroke survivors

Objective To explore the effect of functional electrical stimulation combined with treadmill training and botulinum toxin type A injection on foot-drop and strephenopodia among stroke survivors. Methods Sixty-seven stroke survivors with foot-drop and strephenopodia were randomly divided into an electrical stimulation group (n=23), a conventional treatment group (n=22) and a combined treatment group (n=22). All 3 groups received a 400 U injection of BTX-A and electrical stimulation. After 24 hours, the patients in the conventional treatment group received conventional treatment including a brain protection agent, limb function exercises, gait training, balance training and training in the activities of daily living. The patients in the combined treatment group received that conventional treatment, plus functional electrical stimulation and weight loss training on a treadmill. The patients in the electrical stimulation group received functional electrical stimulation treatment supplementing the conventional treatment. Therapeutic effects were evaluated before and after six weeks of treatment using integral electromyography (iEMS) of the anterior tibial muscle and the lateral head of the gastrocnemius muscle, the co-contraction ratio (CR) during ankle dorsiflexion, the modified Ashworth Scale (MAS), the Berg balance scale (BBS), a functional walking score (FAC), and the active range of motion (AROM) of the ankle in dorsiflexion and eversion. Results After the treatment, significant improvement was observed in all three groups in the average iEMS value of the anterior tibial muscle and the lateral head of the gastrocnemius muscle, the CR in ankle dorsiflexion, and in their MAS, BBS, FAC and AROM results. There was no significant difference among the three groups after treatment in their average iEMS values at the lateral head of the gastrocnemius. The average values of the other indicators were, however, significantly better in the combined treatment group than in the other 2 groups. Conclusion Functional electrical stimulation combined with treadmill training and botulinum toxin type A injection can significantly improve foot-drop, strephenopodia and the walking function of stroke survivors. This combined treatment deserves popularization and application in clinical practice. Key words: Stroke; Botulinum toxin type A; Surface electromyography; Functional electrical stimulation; Exercise; Treadmill training

Relationship between co-contraction ratio and knee adduction moment in knee osteoarthritis subjects

Relationship between co-contraction ratio and knee adduction moment in knee osteoarthritis subjects

Aquatic Therapy Improves Outcomes for Subacute Stroke Patients by Enhancing Muscular Strength of Paretic Lower Limbs Without Increasing Spasticity

The aim of this study was to evaluate the effects of an aquatic exercise program designed to enhance muscular strength in paretic lower limbs in subacute stroke patients. Thirty-six subacute stroke patients were randomly divided to a conventional or an aquatic group (n = 18 each). Outcome measures were assessed at baseline and after 8 wks of training. For the paretic lower limbs, maximum isometric voluntary contraction strength of the rectus femoris and biceps femoris caput longus and the tibialis anterior and lateral gastrocnemius was measured. Cocontraction ratios during knee extension and flexion and ankle dorsiflexion and plantarflexion were calculated respectively. In addition, Modified Ashworth Scale, Functional Ambulation Category, and Barthel Index were assessed. Compared with the conventional intervention, the aquatic intervention resulted in significantly higher knee extension (P = 0.002) and ankle plantarflexion torque (P = 0.002), accompanied with a significantly lower knee extension cocontraction ratio in the paretic limb (P = 0.000). Functional Ambulation Category (P = 0.009) and Barthel Index (P = 0.024) were greater in aquatic group than conventional group posttreatment. Modified Ashworth Scale scores did not show any differences between groups. Aquatic exercise enhanced muscle strength in paretic lower limbs and improved muscle cocontraction without increasing spasticity in subacute stroke patients.

Psychophysiology of women: Sex difference and changes in psychophysiological measures with the menstrual cycle

There is a large and growing body of surface electromyography (sEMG) research using laboratory-specific signal processing procedures (i.e., digital filter type and amplitude normalisation protocols) and data analyses methods (i.e., co-contraction algorithms) to acquire practically meaningful information from these data. As a result, the ability to compare sEMG results between studies is, and continues to be challenging. The aim of this study was to determine if digital filter type, amplitude normalisation method, and co-contraction algorithm could influence the practical or clinical interpretation of processed sEMG data. Sixteen elite female athletes were recruited. During data collection, sEMG data was recorded from nine lower limb muscles while completing a series of calibration and clinical movement assessment trials (running and sidestepping). Three analyses were conducted: (1) signal processing with two different digital filter types (Butterworth or critically damped), (2) three amplitude normalisation methods, and (3) three co-contraction ratio algorithms. Results showed the choice of digital filter did not influence the clinical interpretation of sEMG; however, choice of amplitude normalisation method and co-contraction algorithm did influence the clinical interpretation of the running and sidestepping task. Care is recommended when choosing amplitude normalisation method and co-contraction algorithms if researchers/clinicians are interested in comparing sEMG data between studies.

The co-contraction index of the upper limb for young and old adult cyclists

Bicycling is a popular and convenient means of transportation amongst the elderly in the Netherlands. However, the uptake of the electric bicycle resulted in an increase of single-sided bicycle accidents amongst the elderly (Veiligheid, 2010). Since elderly are prone to severe injuries, bicycle stability is currently a popular research topic. Three main balance strategies have been proposed in former studies: steering as the primary balance strategy and trunk −and lateral knee movement as secondary balance strategies (Moore et al., 2011; Cain, 2013). Since steering is the primary strategy for bicycle stability, the stiffness of the arms plays an important role in active stability during cycling. It has been shown that the arm stiffness of a passive rider is an important factor on the stability of a bicycle (Doria and Tognazzo, 2014). In the study presented here, the co-contraction index (CCI) of the upper limb for young and old adult cyclist is studied. Data is collected during experiments based on the setup described in (Kiewiet et al., 2014), wherein contact forces, muscle activities and motions of the rider and bicycle are measured for 15 young adult (mean±sd: 25.3±2.8 yrs) and 15 old adult (mean±sd: 58.1±2.1 yrs) subjects during unperturbed and perturbed cycling. The arm stiffness is defined as a co-contraction ratio between muscle activity of the m. Biceps Brachii and m. Triceps Lateralis. Results suggest that older adult cyclists use more co-contraction of their arm muscles during cycling, compared to young cyclists. The inter-subject variability of the found CCI was higher for the old adult subject group, compared to the young group. The results support the initial hypothesis that the increase in co-contraction of the upper limb for older cyclists is higher during perturbed cycling compared to unperturbed cycling than for younger cyclists. The findings might give direction towards solutions for increasing the safety and stability for elderly cyclists.

The effect of bilateral trainings on upper extremities muscle activation on level of motor function in stroke patients.

[Purpose] This study was conducted in order to compare muscle activation level on the affected and unaffected limb according to the recovery level of upper limb between bilateral activity with hands clasped and bilateral activity with pilates ring. [Subjects and Methods] Twenty inpatient who have had a stroke were recruited. Subjects were divided into two groups by the Fugl-Meyer Assessment of Motor Function score of moderately recovered group and well recovered group. The muscles activation of upper extremity and Co-Contraction Ratio (CCR) were analyzed. [Results] In the muscles activation of the well group, trapezius, anterior deltoid, and triceps muscles of affected side and biceps muscles of both sides were significantly higher when activity with pilates ring than activity with hands clasped. CCR of both side in the well group was significantly decreased during activity with pilates ring and in the moderate group, CCR of affected side was significantly decreased during activity with pilates ring. [Conclusion] Bilateral activity with a pilates ring is more effective than activity with hands clasped for the facilitation of muscle activation and coordination in stroke patients.

Muscle Recruitment and Coordination following Constraint-Induced Movement Therapy with Electrical Stimulation on Children with Hemiplegic Cerebral Palsy: A Randomized Controlled Trial.

ObjectiveTo investigate changes of muscle recruitment and coordination following constraint-induced movement therapy, constraint-induced movement therapy plus electrical stimulation, and traditional occupational therapy in treating hand dysfunction.MethodsIn a randomized, single-blind, controlled trial, children with hemiplegic cerebral palsy were randomly assigned to receive constraint-induced movement therapy (n = 22), constraint-induced movement therapy plus electrical stimulation (n = 23), or traditional occupational therapy (n = 23). Three groups received a 2-week hospital-based intervention and a 6-month home-based exercise program following hospital-based intervention. Constraint-induced movement therapy involved intensive functional training of the involved hand during which the uninvolved hand was constrained. Electrical stimulation was applied on wrist extensors of the involved hand. Traditional occupational therapy involved functional unimanual and bimanual training. All children underwent clinical assessments and surface electromyography (EMG) at baseline, 2 weeks, 3 and 6 months after treatment. Surface myoelectric signals were integrated EMG, root mean square and cocontraction ratio. Clinical measures were grip strength and upper extremity functional test.ResultsConstraint-induced movement therapy plus electrical stimulation group showed both a greater rate of improvement in integrated EMG of the involved wrist extensors and cocontraction ratio compared to the other two groups at 3 and 6 months, as well as improving in root mean square of the involved wrist extensors than traditional occupational therapy group (p<0.05). Positive correlations were found between both upper extremity functional test scores and integrated EMG of the involved wrist as well as grip strength and integrated EMG of the involved wrist extensors (p<0.05).ConclusionsConstraint-induced movement therapy plus electrical stimulation is likely to produce the best outcome in improving muscle recruitment and coordination in children with hemiplegic cerebral palsy compared to constraint-induced movement therapy alone or traditional occupational therapy.Trial registrationchictr.org ChiCTR-TRC-13004041