Flexor Activity Research Articles

The Effects of Exercise-Induced Muscle Damage on Antagonist Muscles in Upper Limb Reaching Tasks

Coordination and control of multiple muscle groups are critical when adapting to movement disruptions, such as altered goals or pathways. Humans use sensory information from internal and external sources to engage in online movement control. Proprioception, mainly obtained from sensors in the muscles such as muscle spindles, is an important source of sensory information. After intense or unusual exercise, exercise-induced muscle damage (EIMD) can occur within 24 to 48 hours. EIMD can also increase noise in the signals generated by the sensory organs in the muscles and may influence online movement control.
 The objective of the study is to investigate the effects of EIMD on upper-limb movement control.
 Four right-handed, neurologically healthy, female participants (aged 20-21, M = 0.5) took part in the pilot experiment, they had normal, or corrected-to-normal vision, and participated in less than 5 hours of structured strength training weekly. The study consisted of familiarization and baseline testing, an exercise protocol, and a muscle damage assessment. In each session, a maximal voluntary contraction of the biceps brachii was assessed using a dynamometer. This dynamometer was also used for the EIMD-inducing protocol. To test the effects of EIMD on online control, participants completed a series of reaching tasks using the Kinarm Exoskeleton Robot. During some reaches, participants were required to correct their movement to either a force or target perturbation.
 Our pilot data shows that our protocol successfully induced muscle damage, as well as less antagonistic muscle (bicep) activation during reaching tasks. This suggests reduced biceps muscle contribution to movement control post-exercise. A decrease in movement time could signify learning and requires further exploration. We are hopeful that with further data collection, we will establish that participants are less accurate and have reduced flexor muscle activity in responses to both types of perturbations, compared to baseline.

Lunar and mars gravity induce similar changes in spinal motor control as microgravity.

Introduction: Once more, plans are underway to send humans to the Moon or possibly even to Mars. It is therefore, important to know potential physiological effects of a prolonged stay in space and to minimize possible health risks to astronauts. It has been shown that spinal motor control strategies change during microgravity induced by parabolic flight. The way in which spinal motor control strategies change during partial microgravity, such as that encountered on the Moon and on Mars, is not known. Methods: Spinal motor control measurements were performed during Earth, lunar, Mars, and micro-gravity conditions and two hypergravity conditions of a parabola. Three proxy measures of spinal motor control were recorded: spinal stiffness of lumbar L3 vertebra using the impulse response, muscle activity of lumbar flexors and extensors using surface electromyography, and lumbar curvature using two curvature distance sensors placed at the upper and lower lumbar spine. The participants were six females and six males, with a mean age of 33years (standard deviation: 7years). Results: Gravity condition had a statistically significant (Friedmann tests) effect spinal stiffness (p < 0.001); on EMG measures (multifidus (p = 0.047), transversus abdominis (p < 0.001), and psoas (p < 0.001) muscles) and on upper lumbar curvature sensor (p < 0.001). No effect was found on the erector spinae muscle (p = 0.063) or lower curvature sensor (p = 0.170). Post hoc tests revealed a significant increase in stiffness under micro-, lunar-, and Martian gravity conditions (all p's < 0.034). Spinal stiffness decreased under both hypergravity conditions (all p's ≤ 0.012) and decreased during the second hypergravity compared to the first hypergravity condition (p = 0.012). Discussion: Micro-, lunar-, and Martian gravity conditions resulted in similar increases in spinal stiffness, a decrease in transversus abdominis muscle activity, with no change in psoas muscle activity and thus modulation of spinal motor stabilization strategy compared to those observed under Earth's gravity. These findings suggest that the spine is highly sensitive to gravity transitions but that Lunar and Martian gravity are below that required for normal modulation of spinal motor stabilization strategy and thus may be associated with LBP and/or IVD risk without the definition of countermeasures.

Neuromechanical Strategies for Obstacle Negotiation during Overground Locomotion following Incomplete Spinal Cord Injury in Adult Cats.

Following incomplete spinal cord injury in animals, including humans, substantial locomotor recovery can occur. However, functional aspects of locomotion, such as negotiating obstacles, remains challenging. We collected kinematic and electromyography data in 10 adult cats (5 males, 5 females) before and at weeks 1-2 and 7-8 after a lateral mid-thoracic hemisection on the right side of the cord while they negotiated obstacles of three different heights. Intact cats always cleared obstacles without contact. At weeks 1-2 after hemisection, the ipsilesional right hindlimb contacted obstacles in ∼50% of trials, triggering a stumbling corrective reaction or absent responses, which we termed Other. When complete clearance occurred, we observed exaggerated ipsilesional hindlimb flexion when crossing the obstacle with contralesional Left limbs leading. At weeks 7-8 after hemisection, the proportion of complete clearance increased, Other responses decreased, and stumbling corrective reactions remained relatively unchanged. We found redistribution of weight support after hemisection, with reduced diagonal supports and increased homolateral supports, particularly on the left contralesional side. The main neural strategy for complete clearance in intact cats consisted of increased knee flexor activation. After hemisection, ipsilesional knee flexor activation remained, but it was insufficient or more variable as the limb approached the obstacle. Intact cats also increased their speed when stepping over an obstacle, an increase that disappeared after hemisection. The increase in complete clearance over time after hemisection paralleled the recovery of muscle activation patterns or new strategies. Our results suggest partial recovery of anticipatory control through neuroplastic changes in the locomotor control system.SIGNIFICANCE STATEMENT Most spinal cord injuries (SCIs) are incomplete and people can recover some walking functions. However, the main challenge for people with SCIs that do recover a high level of function is to produce a gait that can adjust to everyday occurrences, such as turning, stepping over an obstacle, etc. Here, we use the cat model to answer two basic questions: How does an animal negotiate an obstacle after an incomplete SCI and why does it fail to safely clear it? We show that the inability to clear an obstacle is because of improper activation of muscles that flex the knee. Animals recover a certain amount of function thanks to new strategies and changes within the nervous system.

Effects of tendon elastic energy and electromyographic activity pattern on jumping height and pre-stretch augmentation during jumps with different pre-stretch intensity

ABSTRACT The present study aimed to investigate the effects of tendon elastic energy and electromyographic activity patterns (ratio of pre-landing to concentric: mEMG PLA/CON; ratio of eccentric to concentric; mEMG ECC/CON) on jump performance. Twenty-nine males performed five kinds of unilateral jumps using only ankle joint (no-countermovement jump: noCMJ; countermovement jump: CMJ; drop jumps at 10, 20 and 30 cm drop height: DJ10, DJ20 and DJ30). Jumping height, pre-stretch augmentation and electromyographic activity of the plantar flexor muscles were measured. The elastic energy of the Achilles tendon was measured during isometric contractions. Relative tendon elastic energy (to body mass) was highly correlated with jumping heights of CMJ, DJ10 and DJ20 but not with noCMJ and DJ30, whereas that was significantly correlated with pre-stretch augmentation in CMJ, but not with three DJs. The mEMG PLA/CON was significantly correlated with the pre-stretch augmentation of DJ20 and DJ30, but not with DJ10, whereas the mEMG ECC/CON was significantly correlated with the pre-stretch augmentation of DJ20 and DJ30, but not with CMJ and DJ10. These results suggested that jumping exercises with low pre-stretch intensity benefited from tendon elastic energy, but those with high pre-stretch intensity benefited from electromyographic activity patterns.

Skill-level based examination of forearm muscle activation associated with efficient wrist and finger movements during typing

This study aims to elucidate the relationship between the wrist and finger movements and forearm muscle activation of twelve young people (age: 21.1 ± 0.76 years, nine men and three women) with different typing skills. We hypothesize that skilled typists (STs) could move their wrist and finger joints faster than unskilled typists (UTs) because they could efficiently use their muscles according to the activity characteristics of the flexors and extensors of the wrist joint. We measured wrist and finger movements using a 3D motion capture system and forearm muscle activation using surface electromyography during the typing task. We analyzed the entire task and the time when the U key was entered during the same task. The angular velocity of the wrist and finger flexion/extension and the muscle activation of the wrist flexors was higher in the STs than in the UTs, while the muscle activation of the wrist extensors was higher in the latter than that in the former. Our results showed that STs may have used their forearm muscles to take advantage of the physical characteristics of the keys and the spring characteristics of their muscles and tendons. It was suggested that they placed less mechanical stress on their finger muscles and tendons when pressing and releasing the keys.

Electromyographic analysis of trunk and hip muscles during Yoga poses prescribed for treating chronic low back pain

Yoga is effective for the management of chronic low back pain as it improves muscle strength and endurance. The objective of the current study was to assess trunk and hip muscle activation during Yoga poses usually prescribed for patients with chronic LBP. The study included 22 healthy Yoga trained subjects (mean age: 24.4 ± 2.6 years; 16 females, 6 males). The testing involved collecting surface electromyography data from Rectus Abdominis (RA) and Transverse Abdominis (TA), Gluteus Medius (GM), and Erector Spinae (ES) as subjects attained and held 16 different Yoga poses in standing, kneeling, supine, or prone positions in random order. The signal of each muscle was processed and normalized to its maximum voluntary isometric contraction (MVC). Statistical comparisons were made across selected poses and phases (attaining and holding) for each muscle using repeated-measures ANOVA. The data was also descriptively analyzed for sorting muscle activity. The activation of trunk flexors was significantly higher during boat pose (>50% MVC) followed by plank pose (∼30% MVC), activation of ES was significantly higher during reverse boat (41.7% ± 3.3 MVC) as compared to bow, snake, backward-sway, and warrior poses. The GM activation was significantly less in standing poses than during side-lying and Tiger poses (32–42% MVC). The cat-camel, kneeling camel, downward dog, backward-sway, swaying-palm tree, and warrior poses activated all tested muscles fairly (<20% MVC). The study helps the grading of Yoga positions according to the challenge imposed. The challenging poses may be used to develop graded rehabilitation programs to improve muscle strength/endurance.

Determinants of joint stiffness and jumping height during drop jump.

The present study aimed to examine the effects of muscle-tendon mechanical properties and electromyographic activity on joint stiffness and jumping height and to explore the determinants of joint stiffness and jumping height. Twenty-nine males performed unilateral drop jumps at three drop heights (10, 20, and 30 cm) using only the ankle joint on the sledge apparatus. Ankle joint stiffness, jumping height, and electromyographic activity of the plantar flexor muscles were measured during drop jumps. Active muscle stiffness of the medial gastrocnemius muscle was calculated according to changes in the estimated muscle force and fascicle length during fast stretching at five different angular velocities (100, 200, 300, 500, and 600 deg s-1 ) after submaximal isometric contractions. Tendon stiffness and elastic energy were measured during ramp and ballistic contractions. Active muscle stiffness was significantly correlated with joint stiffness, except for a few conditions. Tendon stiffness measured during ramp and ballistic contractions was not significantly correlated with joint stiffness. The ratios of electromyographic activity before landing and during the eccentric phase to that during the concentric phase were significantly correlated with joint stiffness. In addition, jumping heights at 10 and 20 cm (except for 30 cm) drop heights were strongly associated with the tendon elastic energy, whereas no other measured variables showed significant correlations with jumping heights. These results suggested that (1) joint stiffness is determined by active muscle stiffness and electromyographic activity patterns during jumping, and (2) jumping height is determined by tendon elastic energy.

Low Stiffness Dance Flooring Increases Peak Ankle Plantar Flexor Muscle Activation During a Ballet Jump.

Research in court sports shows that factors which aid in extrinsic shock absorption, that is, flooring and footwear, can help reduce lower extremity injuries. However, since students and performers of ballet or most styles of contemporary dance cannot depend upon footwear, the only extrinsic factor to help them with shock absorption is flooring. We investigated whether doing sauté on a low stiffness dance floor produced a difference in EMG output of the vastus lateralis, gastrocnemius, of soleus compared to a high stiffness floor. Average and average peak amplitude EMG output from 18 dance students or active dancers performing 8 repetitions of sauté on a low stiffness floor (Harlequin® Woodspring) was compared to a maple hardwood floor on concreted subflooring. The data showed a significant increase in average peak EMG muscle amplitude during jumping on the low stiffness floor compared to a high stiffness floor for the soleus muscle (P = .033) and a trend for increase average peak output for the medial gastrocnemius (P = .088). The difference in average peak amplitude of EMG output is explained through the difference in force absorption between floors. With the high stiffness floor, more force of the landing was returned to the dancers' legs, but the low stiffness floor absorbed some of the force of landing the jump, and therefore muscles needed to contribute more to maintain the same jump height. The force absorption characteristic of the low stiffness floor may decrease injury rates in dance through causing an adjustment in muscle velocity. Rapid eccentric muscle activity carries the greatest possibility of musculotendinous injury and is experienced in lower body muscles controlling all joints during impact absorption, which includes landing of jumps in dance. If a surface can decelerate the landing of a high velocity dance movement, it also decreases the musculotendinous demand for high velocity tension generation.

Characteristics of uneven surface walking in stroke patients: Modification in biomechanical parameters and muscle activity

BackgroundStroke patients have difficulty walking in outdoor environments, including uneven surfaces, reducing their opportunities for social participation. Changes in stroke patients’ gait while walking on even surfaces have been reported; however, gait alterations on uneven surfaces remain unclear. Research questionTo what extent do biomechanical parameters and muscle activity during even and uneven surface walking differ between stroke patients and healthy people? MethodsTwenty stroke patients and 20 age-matched healthy people walked on a 6 m even and uneven surfaces. Data on gait speed, root mean square (RMS) of trunk acceleration as a measure of gait stability, maximum joint angle, average muscle activity, and muscle activity time were quantified using accelerometers attached to the trunk, video camera images, and electromyography of lower extremities. A two-factor mixed-model analysis of variance was used to test the effects of group, surface, and group × surface interactions. ResultsGait speed decreased (p < 0.001) on the uneven surface in stroke patients and healthy people. RMS showed an interaction (p < 0.001), and the post-hoc test revealed an increase in stroke patients in the mediolateral direction during the swing phase on the uneven surface. The hip extension angle during the stance phase showed an interaction (p = 0.023), and the post-hoc test revealed a decrease in stroke patients on the uneven surface. The soleus muscle activity time showed an interaction during the swing phase (p = 0.041), and the post-hoc test revealed an increase in stroke patients compared to healthy people only on the uneven surface. SignificanceWhile walking on an uneven surface, stroke patients showed decreased gait stability, decreased hip extension angle during stance phase, and increased ankle plantar flexor activity time during swing phase. These changes may result from impaired motor control and compensatory strategies used by stroke patients on uneven surfaces.

Corticomuscular and intermuscular coherence are correlated after stroke: a simplified motor control?

During movement, corticomuscular coherence is a measure of central-peripheral communication, while intermuscular coherence is a measure of the amount of common central drive to the muscles. Although these two measures are modified in stroke subjects, no author has explored a correlation between them, neither in stroke subjects nor in healthy subjects. Twenty-four chronic stroke subjects and 22 healthy control subjects were included in this cohort study, and they performed 20 active elbow extension movements. The electroencephalographic and electromyographic activity of the elbow flexors and extensors were recorded. Corticomuscular and intermuscular coherence were calculated in the time-frequency domain for each limb of stroke and control subjects. Partial rank correlations were performed to study the link between these two variables. Our results showed a positive correlation between corticomuscular and intermuscular coherence only for stroke subjects, for their paretic and non-paretic limbs (P < 0.022; Rho > 0.50). These results suggest, beyond the cortical and spinal hypotheses to explain them, that stroke subjects present a form of simplification of motor control. When central-peripheral communication increases, it is less modulated and more common to the muscles involved in the active movement. This motor control simplification suggests a new way of understanding the plasticity of the neuromuscular system after stroke.

Does human foot anthropometry relate to plantar flexor fascicle mechanics and metabolic energy cost across various walking speeds?

Foot structures define the leverage in which the ankle muscles push off against the ground during locomotion. While prior studies have indicated that inter-individual variation in anthropometry (e.g. heel and hallux lengths) can directly affect force production of ankle plantar flexor muscles, its effect on the metabolic energy cost of locomotion has been inconclusive. Here, we tested the hypotheses that shorter heels and longer halluces are associated with slower plantar flexor (soleus) shortening velocity and greater ankle plantar flexion moment, indicating enhanced force potential as a result of the force-velocity relationship. We also hypothesized that such anthropometry profiles would reduce the metabolic energy cost of walking at faster walking speeds. Healthy young adults (N=15) walked at three speeds (1.25, 1.75 and 2.00 m s-1), and we collected in vivo muscle mechanics (via ultrasound), activation (via electromyography) and whole-body metabolic energy cost of transport (via indirect calorimetry). Contrary to our hypotheses, shorter heels and longer halluces were not associated with slower soleus shortening velocity or greater plantar flexion moment. Additionally, longer heels were associated with reduced metabolic cost of transport, but only at the fastest speed (2.00ms-1, R2=0.305, P=0.033). We also found that individuals with longer heels required less increase in plantar flexor (soleus and gastrocnemius) muscle activation to walk at faster speeds, potentially explaining the reduced metabolic cost.

Inhibitory Effects of Prolonged Focal Muscle Vibration on Maximal Grip Strength and Muscle Activity of Wrist and Extrinsic Finger Flexor Muscles

ObjectiveThe objective of this study was to identify effective stimulus time by quantifying the inhibitory effects of focal muscle vibration (FMV) on maximal grip strength and muscle activities of the wrist and extrinsic finger flexors. MethodsA randomized repeated-measures design was used in this study. A total of 22 healthy volunteers (mean age, 20.9 years) participated. An FMV of 86 Hz was applied to the anterior surface of the distal forearm under the following 3 conditions: no FMV (control), 5-minute FMV, and 10-minute FMV. Maximal grip strength was measured before and after FMV. The muscle activities of the flexor digitorum superficialis, flexor digitorum profundus (FDP), and flexor carpi ulnaris were simultaneously recorded using surface electromyography. Discomfort and complications following FMV were also assessed. ResultsCompared with the control group, a significant decrease in muscle activity was observed in both the flexor digitorum superficialis and flexor carpi ulnaris after 5 and 10 minutes of FMV. In contrast, there was no significant decrease in the maximal grip strength or FDP muscle activity after either FMV condition. The discomfort was significantly higher immediately after both FMV conditions than in the control group, but it decreased 15 minutes after FMV, indicating no significant difference among the 3 conditions. Redness and/or swelling were observed in 13.6% and 36.3% of the participants after 5 and 10 minutes of FMV, respectively. ConclusionFive-minute FMV to the distal forearm could be a useful therapeutic method with few complications. However, the FMV in this area alone was not sufficient to suppress the muscle activity of the FDP located in the deep layer.

Teaching Video NeuroImages: Acquired focal neuromyotonia in LGI-1 autoimmunity

An 81-year-old woman was diagnosed with corticobasal degeneration (cognitive decline and left hand posturing). Hyponatremia and bilateral faciobrachial dystonic seizures (FBDS) ensued. Neurologic examination (figure, A; video) revealed persistent involuntary continuous left 3rd and 4th finger flexor activation and delayed relaxation. EMG revealed high-frequency spontaneous discharges, including neuromyotonia and fast myokymia of the left flexor digitorum superficialis and pronator teres (figure, B). LGI1 immunoglobulin G (IgG)1 was detected, but not CASPR2-IgG (figure, C–E). Oncologic evaluation revealed breast ductal carcinoma in situ. Encephalopathy and FBDS resolved after IV immunoglobulin. Encephalopathy coexisting with peripheral nerve hyperexcitability can mimic neurodegeneration, and should prompt exclusion of LGI1/CASPR2 autoimmunity.2

Immediate neck hypoalgesic effects of craniocervical flexion exercises and cervical retraction exercises among individuals with non-acute neck pain and a directional preference for retraction or extension: preliminary pretest-posttest randomized experimental design

ABSTRACT Background Selective deep neck flexor muscle activation through craniocervical flexion exercises has been considered to be different from cervical retraction exercises. Objective To compare the immediate analgesic effect of craniocervical flexion versus cervical retraction exercises in individuals with nonacute, directional preference (DP) for cervical retraction or extension Methods A two-arm, assessor-blinded, pretest-posttest randomized experiment was conducted. Participants were randomly assigned to either craniocervical flexion or cervical retraction exercises and those who were confirmed at the post-intervention examination to have a DP for cervical retraction or extension were analyzed. The primary outcome measure was pressure pain thresholds at the C2 and C5-C6 levels. Results A total of 10 (mean age = 20.6 years) and nine participants (mean age = 19.4 years) undertook craniocervical flexion and retraction exercises, respectively. One-way analysis of variance demonstrated no statistically significant (p > 0.05) interaction effect regardless of the neck level. In the pre-post change percentages, retraction exercises provided greater analgesic effects compared to craniocervical flexion exercises at the C2 (Hedges’ g = 0.679) and C5-C6 levels (g = 0.637). Conclusion This study showed a comparable or greater immediate neck analgesic effect from cervical retraction exercises compared to craniocervical flexion exercises in individuals with a DP for cervical retraction or extension.

Characterization of the influence of the dominant tract on hand closing post stroke based on the Fugl-Meyer score

While stroke survivors with moderate or mild impairment are typically able to open their hand at will, those with severe impairment cannot. Abnormal synergies govern the arm and hand in stoke survivors with severe impairment, so hand opening, which is required to overcome the working synergy, is an extremely difficult task for them to achieve. It is universally accepted that alternative tracts including the cortico-reticulospinal tract (CRST), employed in the case that the corticospinal tract (CST) is damaged by stroke, brings about such abnormal synergies. Here we note that hand closing is enabled by alternative tracts as well as the CST, and a research question arises: Does motor characteristics while closing the hand depend on the integrity of the CST? In this study, we evaluate the abilities of 17 stroke survivors to flex and relax the metacarpophalangeal (MCP) joints and investigate whether motor characteristics can be distinguished based on CST integrity which is estimated using upper-extremity Fugl-Meyer (UEFM) scores. UEFM scores have been perceived as an indirect indicator of CST integrity. We found that participants with the UEFM score above a certain value, who are assumed to use the CST, moves the MCP joints more smoothly (P < 0.05) and activates the flexors to flex the joints faster (P < 0.05), in comparison to participants with low UEFM scores, who are assumed to preferentially use alternative tracts. The results imply that use of alternative tracts (i.e. the CRST) results in a degradation in movement smoothness and slow activation of MCP flexors. We present evidence that responses of flexors of the MCP joints following stroke depend on the degree of impairment which is hypothesized to originate from preferentially use of different neural motor pathways.

The Evaluation of Asymmetry in Isokinetic and Electromyographic Activity (sEMG) of the Knee Flexor and Extensor Muscles in Football Players after ACL Rupture Reconstruction and in the Athletes following Mild Lower-Limb Injuries.

This study was aimed at evaluating knee stabilizer (quadriceps and hamstring) muscle strength and the medio-lateral symmetry of hamstring fatigue in football players after ACL reconstruction and with mild lower extremity injuries. The study comprised 65 professional football players who were divided into three groups: Group 1 (n = 24; 22.7 ± 3.6 years; 175 ± 4 cm; 77.3 ± 7.6 kg) after ACL reconstruction, Group 2 (n = 21; 20.5 ± 3.7 years; 177 ± 6 cm; 74.3 ± 9.1 kg) with mild lower-limb injuries (grade 1 muscle strains) and Group 3 (n = 20; 23.1 ± 2.8 years; 178 ± 6 cm; 75.8 ± 8.8 kg) without injuries in the past 3 years. The concentric isokinetic test (10 knee flexions and extensions at 60, 180 and 300°/s with a 30 s interval for rest) was performed on both limbs. Fatigue symmetry between the medial and lateral hamstrings was measured with sEMG during 60 s of isometric contractions. In comparison to the other groups, the injured leg demonstrated significantly lower values of peak torque for the quadriceps (G1-G2 = 48%, 38%, 14%; G1-G3 = 49%, 25%, 14%) and hamstring muscles (G1-G2 = 36%, 35%, 18%; G1-G3 = 64%, 28%, 17%) as well as lower values of hamstring muscle work (G1-G2 = 262 J, 157 J; G1-G3 = 219 J, 179 J) and power (G1-G2 = 34 W; 11 W; G1-G3 = 29 W, 12 W). No significant differences were noted in strength between Groups 2 and 3. The significantly higher fatigue of the BF compared to the SEM muscle was seen in Group 1 for the involved (mean difference = 0.12) and uninvolved limbs (mean difference = -0.10), but in Group 2, a non-significant trend towards asymmetry was also noted. No asymmetry in hamstring muscle fatigue was determined in Group 3. The results of our study allow us to indicate that active football players who previously met the RTS criteria, had deficits in lower-limb muscle performance 2-3 years after reconstruction, which could lead to ACL re-injury. This observation is potentially of importance because these deficits may not be subjectively reported by such athletes and also may not be visible in regular orthopedic and physiotherapeutic assessment.

Variation of body weight supported treadmill training parameters during a single session can modulate muscle activity patterns in post-stroke gait

Evidence supporting the benefits of locomotor training (LT) to improve walking ability following stroke are inconclusive and could likely be improved with a better understanding of the effects of individual parameters i.e., body weight support (BWS), speed, and therapist assistance and their interactions with walking ability and specific impairments. We evaluated changes in muscle activity of thirty-seven individuals with chronic stroke (> 6 months), in response to a single session of LT at their self-selected or fastest-comfortable speed (FS) with three levels of BWS (0%, 15%, and 30%), and at FS with 30% BWS and seven different combinations of therapist assistance at the paretic foot, non-paretic foot, and trunk. Altered Muscle Activation Pattern (AMAP), a previously developed tool in our lab was used to evaluate the effects of LT parameter variation on eight lower-extremity muscle patterns in individuals with stroke. Repeated-measures mixed-model ANOVA was used to determine the effects of speed, BWS, and their interaction on AMAP scores. The Wilcoxon-signed rank test was used to determine the effects of therapist-assisted conditions on AMAP scores. Increased BWS mostly improved lower-extremity muscle activity patterns, but increased speed resulted in worse plantar flexor activity. Abnormal early plantar flexor activity during stance decreased with assistance at trunk and both feet, exaggerated plantar flexor activity during late swing decreased with assistance to the non-paretic foot or trunk, and diminished gluteus medius activity during stance increased with assistance to paretic foot and/or trunk. Therefore, different sets of training parameters have different immediate effects on activation patterns of each muscle and gait subphases.

Cortical, muscular, and kinetic activity underpinning attentional focus strategies during visuomotor control.

Focusing internally on movement control or bodily sensations is frequently shown to disrupt the effectiveness and efficiency of motor control when compared to focusing externally on the outcome of movement. Whilst the behavioral consequences of these attentional strategies are well-documented, it is unclear how they are explained at the corticomuscular level. The aim of the present study was to investigate how attentional focus strategies affect kinetic, cortical, muscular, and corticomuscular activity during an isometric force precision task. In a repeated measures design, we measured force, EEG and EMG activity from twenty-seven participants who performed isometric contractions of the right hand whilst encouraged to adopt either an internal or external focus through a combination of instructions, secondary tasks, and self-report evaluations. Results indicated that focusing internally led to poorer force accuracy and steadiness compared to an external focus. An internal focus also increased muscle activity of the forearm flexor, increased EEG alpha activity across the parieto-occipital cortex, lowered frontal midline EEG theta activity, and lowered beta corticomuscular coherence between the forearm flexor and contralateral motor cortex. The results of this study provide a holistic understanding of how attentional focus strategies alter corticomuscular control during an isometric force precision task, paving the way for exploring how the behavioral consequences of attentional strategies can be explained at the corticomuscular levels across a wide range of motor tasks and contexts.

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

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

Force Generation and Muscle Activation of Knee Extensor and Flexor Muscles in Type 2 Diabetes Mellitus Patients.

Type 2 diabetes mellitus (T2DM) is associated with decreased muscle force generation. The disturbed force generation process in T2DM could be attributed to either or both agonist and antagonist muscles activation. The present study aims to assess the effects of T2DM on the interaction of antagonist and agonist muscles in the knee joint. The peak torque, root mean square (RMS) of the SEMG signals, the ratio of torque/RMS, and the interaction of antagonists and agonist muscles were compared between healthy and T2DM patients. Surface ElectroMyoGraphy (SEMG) of knee flexor and extensor muscles were recorded during concentric contraction with an isokinetic dynamometer at 60°/s in 13 T2DM and 12 healthy subjects. The independent sample t-tests were used to compare diabetic and healthy subjects. The significance level was set at 0.05. The antagonist/agonist interaction during maximal extension (P = 0.010) and flexion (P = 0.022) torques of the knee joint showed significantly lower activation of antagonist muscles in T2DM patients than in healthy subjects. Lower knee flexion (41.3%) and extension torques (49.1%) and RMS of agonist and antagonist muscles were observed in T2DM. The torque/RMS ratio (P > 0.05) showed no significant differences in T2DM and healthy subjects. The reduced maximal knee flexor and extensor torques in T2DM are accompanied with the decreased myoelectric activity of corresponding muscles. The related mechanism could be attributed to lower values of antagonist/agonist interaction, which may point out some neural compensatory processes to preserve the functional capacity of the neuromuscular system in T2DM.