Effect of a task's postural demands on medial longitudinal arch deformation and activation of foot intrinsic and extrinsic musculatur.

PURPOSE: It is not well established how motion and muscle activation of the medial longitudinal arch (MLA) of the foot vary under different loading conditions. Intrinsic and extrinsic foot muscles may play a role in postural control, which may be investigated by comparing loading tasks with differing postural demands. The objective of this study was to investigate the interaction of MLA flexibility and loading task on muscle activation. METHODS: Twenty healthy adults completed two instrumented single-foot loading tasks: controlled external load of 50% body weight while sitting and bilateral standing. Fine-wire intramuscular and surface electromyography collected flexor hallucis brevis, abductor hallucis, tibialis posterior, flexor hallucis longus, tibialis anterior, and peroneus longus activation. MLA deformation was measured as a percent change in navicular height with loading. RESULTS: During seated external loading, greater MLA deformation was associated with greater muscle activation for all instrumented muscles (R² = 0.224-0.303, p < 0.05) except for tibialis anterior. During bilateral stance, there were no correlations between MLA deformation and muscle activation. Activation of all extrinsic muscles except for tibialis anterior were greater during bilateral standing than during external loading ( p = 0.002-0.013), indicating activation of these muscles was caused by postural demands of the standing task, not simply load. CONCLUSIONS: MLA deformation and muscle activation are strongly task-dependent.

Development of a training paradigm for voluntary control of the peri-auricular muscles: a feasibility study.

BACKGROUND: Spinal cord injury (SCI) can lead to severe and permanent functional deficits. In humans, peri-auricular muscles (PAMs) do not serve any physiological function, though their innervation is preserved in even high level SCI. Auricular control systems provide a good example of leveraging contemporary technologies (e.g., sEMG controlled computer games) to enable those with disabilities. Our primary objective is to develop and test the effectiveness of an auricular muscle training protocol to facilitate isolated and coordinated, bilateral voluntary control that could be used in individuals without volitional control of the vestigial PAMs. METHODS: Seventeen non-disabled persons were screened; 13 were eligible and 10 completed the entire protocol. The facilitation phase, included one session of sub-motor threshold, sensory electrical stimulation followed by neuromuscular electrical stimulation paired with ear movement feedback for up to 8 additional sessions. Participants progressed to the skill acquisition phase where they dawned an auricular control device that used sEMG signals to control movements of a cursor through three levels of computer games, each requiring increasingly more complex PAM coordination. RESULTS: The 10 who completed the protocol, finished the facilitation phase in 3 to 9 sessions and achieved some level of voluntary auricle movement that ranged between 1 and 5 mm. Qualitative analysis of longitudinal post-session auricular movement, revealed two subgroups of learners. Six successfully completed all 3 games-the "Learners". Two were partially successful in game completion and two were unable to complete a single game--"Poor/Non-Learners". Quantitative analysis revealed a significant group difference in auricular amplitude for both facilitation and skill phases (p < .05), and a significant relationship between performance in the two phases (R2 = 0.84, p = 0.004). CONCLUSION: Sixty percent of those who completed the facilitation phase were able to learn and demonstrate functional voluntary control of the vestigial PAMs. Those who progressed the fastest through facilitation were also those who were most proficient in skill acquisition with the device. There was considerable variability in progression through the two-phase protocol, with 20% deemed Poor/Non-Learners and unable to complete even the most basic game following training. There were no serious adverse events. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02358915 , first posted February 9, 2015.

Ankle muscle tenotomy does not alter ankle flexor muscle recruitment bias during locomotor-related repetitive limb movement in late-stage chick embryos.

In ovo, late-stage chick embryos repetitively step spontaneously, a locomotor-related behavior also identified as repetitive limb movement (RLM). During RLMs, there is a flexor bias in recruitment and drive of leg muscle activity. The flexor biased activity occurs as embryos assume an extremely flexed posture in a spatially restrictive environment 2-3 days before hatching. We hypothesized that muscle afferent feedback under normal mechanical constraint is a significant input to the flexor bias observed during RLMs on embryonic day (E) 20. To test this hypothesis, muscle afference was altered either by performing a tenotomy of ankle muscles or removing the shell wall restricting leg movement at E20. Results indicated that neither ankle muscle tenotomy nor unilateral release of limb constraint by shell removal altered parameters indicative of flexor bias. We conclude that ankle muscle afference is not essential to ankle flexor bias characteristic of RLMs under normal postural conditions at E20.

Blunted Myoglobin and Quadriceps Soreness After Electrical Stimulation During the Luteal Phase or Oral Contraception.

PURPOSE: Acute muscle damage after exercise triggers subsequent regeneration, leading to hypertrophy and increased strength after repeated exercise. It has been debated whether acute exercise-induced muscle damage is altered under various premenopausal estrogen conditions. Acute contraction-induced muscle damage was compared during exogenous (oral contraceptive, OC), endogenous (luteal phase, HI), or low (menses, LO) estrogen in healthy young women aged 21 to 30 years old. METHODS: Women (OC, n = 9; HI, n = 9; LO, n = 8; total N = 26) performed 1 neuromuscular electrical stimulation (NMES) bout. Soreness, measured via visual analog scale and the Likert Scale of Muscle Soreness for Lower Limb (LSMSLL), quadriceps strength, and plasma myoglobin (Mb), interleukin (IL)-6, IL-8, and granulocyte-colony stimulating factor were measured before and after NMES. RESULTS: NMES performance was similar across groups. Meaningful within-group increases in Mb (effect size [ES] = 1.12) and IL-8 (ES = 0.38) occurred in LO; ES for HI and OC were trivial. ES of the between-group difference in change was moderate for Mb (LO vs. HI = 1.15) and IL-8 (LO vs. HI = 0.86; LO vs. OC = 0.73). 17-ß estradiol correlated moderately and negatively with Mb relative change (r = -.52, p < .05). LO had ~5% greater strength loss than OC and HI. The mean change score for the LSMSLL 2 days post-NMES was clinically greater in LO than OC or HI. CONCLUSIONS: Acute NMES-induced indicators of muscle fiber damage and qualitative muscle soreness may be attenuated during the luteal phase or active OC pill consumption compared with the menstrual phase.

Effectiveness of neuromuscular electrical stimulation for management of shoulder subluxation post-stroke: a systematic review with meta-analysis.

OBJECTIVES: To examine the effectiveness of neuromuscular electrical stimulation (NMES) for the management of shoulder subluxation after stroke including assessment of short (1 hour or less) and long (more than one hour) daily treatment duration. DATA SOURCES: MEDLINE, CENTRAL, CINAHL, WOS, KoreaMed, RISS and reference lists from inception to January 2017 Review methods: We considered randomized controlled trials that reported neuromuscular electrical stimulation for the treatment of shoulder subluxation post-stroke. Two reviewers independently selected trials for inclusion, assessed trial quality, and extracted data. RESULTS: Eleven studies were included (432 participants); seven studies were good quality, four were fair. There was a significant treatment effect of neuromuscular electrical stimulation for reduction of subluxation for persons with acute and subacute stroke (SMD:-1.11; 95% CI:-1.53, -0.68) with either short (SMD:-0.91; 95% CI:-1.43, -0.40) or long (SMD:-1.49; 95% CI:-2.31, -0.67) daily treatment duration. The effect for patients with chronic stroke was not significant (SMD:-1.25; 95% CI:-2.60, 0.11). There was no significant effect of neuromuscular electrical stimulation on arm function or shoulder pain. CONCLUSION: This meta-analysis suggests a beneficial effect of neuromuscular electrical stimulation, with either short or long daily treatment duration, for reducing shoulder subluxation in persons with acute and subacute stroke. No significant benefits were observed for persons with chronic stroke or for improving arm function or reducing shoulder pain.

The Influence of a Bout of Exertion on Novice Barefoot Running Dynamics.

Barefoot, forefoot strike (FFS) running has recently risen in popularity. Relative to shod, rear-foot strike (RFS) running, employing a FFS is associated with heightened triceps surae muscle activation and ankle mechanical demand. Novice to this pattern, it is plausible that habitually shod RFS runners exhibit fatigue to the triceps surae when acutely transitioning to barefoot running, thereby limiting their ability to attenuate impact. Therefore, the purpose was to determine how habitually shod RFS runners respond to an exertion bout of barefoot running, operationally defined as a barefoot run 20% of mean daily running distance. Twenty-one RFS runners performed novice barefoot running, before and after exertion. Ankle peak torque, triceps surae EMG median frequency, foot-strike patterns, joint energy absorption, and loading rates were evaluated. Of the 21 runners, 6 maintained a RFS, 10 adopted a mid-foot strike (MFS), and 5 adopted a FFS during novice barefoot running. In-response to exertion, MFS and FFS runners demonstrated reductions in peak torque, median frequency, and ankle energy absorption, and an increase in loading rate. RFS runners demonstrated reductions in peak torque and loading rate. These results indicate that a short bout of running may elicit fatigue to novice barefoot runners, limiting their ability to attenuate impact. Key pointsIn response to exertion, novice barefoot runners demonstrate fatigue to their soleus.In response to exertion, novice barefoot runners demonstrate a reduction in ankle energy absorptionIn response to exertion, novice barefoot runners demonstrate an increase in loading rate.

Therapeutic application of electrical stimulation and constraint induced movement therapy in perinatal brachial plexus injury: A case report.

Infants and children with perinatal brachial plexus injury (PBPI) have motion limitations in the shoulder, elbow, forearm and hand that are dependent on the level of injury and degree of recovery. The injury and subsequent recovery period occur during critical periods of central and spinal neural development placing infants and children at-risk for developmental disregard and disuse of the affected arm and hand. A case report outlines the therapy and surgical interventions provided in the first 2 years of life for a child with global PBPI and a positive Horner's sign. Electrical stimulation and constraint induced movement therapy provided sequentially were effective therapy interventions. Neurosurgery to repair the brachial plexus was performed at an optimal time period.(2) The Assisting Hand Assessment,(12) Modified Mallet(13) and Active Movement Scale(14) are effective outcome measures in PBPI and served as valuable guides for therapy intervention. Oxford Level of Evidence: 3b; Individual Case Control Study.

Spectral analysis of EMG using intramuscular electrodes reveals non-linear fatigability characteristics in persons with chronic low back pain.

Greater fatigability across lumbar extensors has been reported in persons with chronic low back pain (LBP), however, extensor atrophy tends to be local to the site of pain. Therefore, specific ultrasound guided local and remote intramuscular electromyographic recordings were undertaken during an isometric horizontal trunk hold in two carefully matched cohorts; persons with and without LBP. The test was performed to self-determined maximal hold time, and the control group held the horizontal position longer (P < 0.001). A power spectral analysis was performed to calculate the normalized median frequency (NMF) slope for both the first and last 30s of the fatigue test due to the group difference in hold times. There were no significant group differences in NMF slope at the first 30s of testing (P = 0.650). The NMF slope for the first and last 30s was not different in healthy subjects (P = 0.688), but was different in persons with LBP, illustrated by shallowing of the slope at the last 30s of the test (P = 0.008). A between muscle comparison in the LBP group showed greater non-linear behavior in the deep multifidus (painful region) in contrast to T10 longissimus thoracis (nonpainful region) (P = 0.013). Possible explanations for these findings are discussed.

Unique hue loci differ with methodology.

BACKGROUND: Studies investigating the effect of rods on unique hue loci in the peripheral retina generally obtain measures at two time points associated with the dark adaptation function - the cone plateau and the rod plateau. In comparison, this study used a color-naming procedure to identify the loci of unique green and unique yellow as a function of time associated with the entire dark adaptation function. The unique hue loci derived by this procedure were then compared to those obtained directly with a staircase procedure. METHOD: Hue-scaling functions were obtained for monochromatic stimuli for four observers using the '4 + 1' procedure. Data were collected every 4 min following extinction of a bleaching stimulus. These hue-scaling functions were then converted to uniform appearance diagrams (UADs) to derive unique green and unique yellow loci. Unique green and unique yellow loci were also obtained from the same observers via a staircase procedure at 4-9 min post-bleach (minimal rod input) and after 28 min dark adaptation (maximal rod input). Measurements were made in the peripheral retina at 10° temporal retinal eccentricity and at the fovea. RESULTS: Unique green loci derived from UADs are at longer wavelengths compared to those measured directly with the staircase procedure. In addition, unique green loci derived from UADs show a progressive shift to longer wavelengths as time post-bleach increases; whereas, unique green loci obtained from the staircase procedure differ little between the rod-bleach and no-bleach conditions. Unique yellow loci are similar across both experimental procedures. CONCLUSION: Unique green loci derived from UADs are not the same as those measured with traditional psychophysical procedures. These differences may be due to the different response criteria used by observers in the color-naming and staircase procedures. The unique green loci obtained from UADs indicate that rod signals shift unique green loci to longer wavelengths as time post-bleach increases. More direct methods need to be employed to determine if this rod effect is valid.

Recruitment and comfort of BION implanted electrical stimulation: implications for FES applications.

Restoration of motor function to paralyzed limbs by functional electrical stimulation (FES) has been hampered by the lack of precise and gradual control over muscle recruitment. A suitable interface should provide selective stimulation of individual muscles with graded recruitment of force. The BION was developed to enable neuromuscular stimulation through a miniature, self-contained implant designed to be injected in or near muscles and peripheral nerves. In this study, recruitment properties and comfort of the BION implanted electrical stimulation were systematically evaluated in subjects who participated in a clinical trial. Recruitment properties were qualitatively similar to other methods of implanted neuromuscular stimulation: thresholds and steepness of recruitment were negatively correlated and depended on stimulus charge (product of pulse current and duration). Perceived comfort was not affected by the choice of stimulus parameters, thus their choice can be based purely on technical considerations such as efficiency or resolution of recruitment.

Mechanical loading of rigid intramuscular implants.

Several groups are developing different versions of a new class of leadless, permanently implanted electronic devices with a size and form factor that allows them to be injected into muscles (BIONs). Their circuitry is protected from body fluids by thin-walled hermetic capsules made from rigid and brittle materials (glass or ceramic) that include feedthroughs to their electrodes. These packages experience repetitive stresses from the very contractions that they excite. We here provide a worst-case analysis of such stresses and methods for testing and validation of devices intended for such usage, along with the failure analysis and remediation strategy for a design that experienced unanticipated failures in vivo.

The BION devices: injectable interfaces with peripheral nerves and muscles.

OBJECT: The purpose of this study was to describe a novel technology for implantable neuromuscular stimulation to treat complications of paralysis and disuse atrophy, including shoulder subluxation, hand contractures, drop foot, and osteoarthritis. The authors review the results so far of several pilot clinical studies of these muscle stimulation devices. METHODS: Miniature wireless stimulators received power and individually addressed command signals from an external radiofrequency transmission coil. One or more implants were injected through a 12-gauge hypodermic insertion tool into muscles or adjacent to motor nerves, where they provided the means to activate the muscles in any desired pattern of intensity and frequency. Randomized controlled studies in small numbers of patients are underway to identify efficacy, acceptability, best methods of practice, and any design changes that may be required to improve the technology. Fifty patients have been enrolled in five studies; 35 patients have undergone implantation of a total of 79 BION1 devices. Comparisons with surface stimulation in patients who have suffered a stroke with shoulder subluxation and hand contractures show similar improvements in objective measures of efficacy but higher comfort levels for stimulation by implants. CONCLUSIONS: Injected microstimulators represent a promising new class of technology for the rehabilitation of patients with upper motor neuropathies. As the technology evolves, practitioners may be able to use it to facilitate functional reanimation of paralyzed limbs.

Effect of an electric stimulation facilitation program on quadriceps motor unit recruitment after stroke.

OBJECTIVE: To compare maximum voluntary isometric torque (MVIT) and motor unit recruitment of the quadriceps after an electric stimulation facilitation program in persons affected by cerebrovascular accident (CVA). DESIGN: Three-week, randomized controlled trial with an electric stimulation facilitation program added to standard care. SETTING: Inpatient rehabilitation center. PARTICIPANTS: Twenty patients receiving rehabilitation for first-time CVA (51.8+/-15.2 y; days post-CVA, 38.4+/-40.0 d). Patients were randomly assigned to study and control groups. INTERVENTIONS: All patients received standard physical therapy (PT) care. In addition, the study group received an electric stimulation facilitation program during weight-bearing and ambulatory activities of the PT program. MAIN OUTCOME MEASURES: MVIT and motor unit recruitment measured by interpolated twitch testing. A 2 x 4 repeated-measures analysis of variance was performed on measurements at 4 intervals: pretest, 1 week, 2 weeks, and 3 weeks. RESULTS: MVIT increased by 77% in patients receiving electric stimulation, compared with a 31% increase for the control group. There was a significant effect for assessment time only. Motor unit recruitment increased from 35% to 53% for the study group, whereas the control group recorded no change in recruitment ability. A significant interaction was recorded, indicating improved motor unit recruitment for the study group. CONCLUSIONS: A brief and dynamic electric stimulation facilitation program significantly improved motor unit recruitment in persons after CVA.