Applications of EMG in Clinical and Sports Medicine

This second of two volumes on EMG (Electromyography) covers a wide range of clinical applications, as a complement to the methods discussed in volume 1. Topics range from gait and vibration analysis, through posture and falls prevention, to biofeedback in the treatment of neurologic swallowing impairment. The volume includes sections on back care, sports and performance medicine, gynecology/urology and orofacial function. Authors describe the procedures for their experimental studies with detailed and clear illustrations and references to the literature. The limitations of SEMG measures and methods for careful analysis are discussed. This broad compilation of articles discussing the use of EMG in both clinical and research applications demonstrates the utility of the method as a tool in a wide variety of disciplines and clinical fields

The effect of mechanical vestibular stimulation on muscle tone and spasticity in individuals with neurological impairment

In the desire to better understand spasticity mainly in Cerebral Palsy (CP) and to examine vestibular stimulation as a future intervention for .muscle tone reduction, and to be able to describe the change in level of spasticity in subjects with disability and describe interventions effects, a series of experiments are done on children with spasticity. In addition to understanding the otoliths in the vestibular system and their projections, properties and pathways a more important major objective of this work is to validate the changes in otoliths signal caused by vestibular stimulation based on the Equilibrium Point Hypothesis and the inclusion of EMG data in assessing the level of spasticity. Stimulation to the saccule in the otolith is induced to reduce spasticity. The otoliths are sensitive to acceleration, and detect the direction and magnitude of gravity, as well as transient linear accelerations due to movement. This is a form of a biological accelerometer. The vestibular mechanical stimulation is provided using a vertical stimulation chair that moves up/down at a constant frequency of 2 Hz and amplitude of ~ 7.5 centimeter for time duration of 15 minutes. This form of stimulation targets the saccule organ in the vestibular system, which results in alterations of the descending signals of the vestibular system responsible for setting tone of the antigravity muscles. Electromyography (EMG) is simultaneously recorded from the quadriceps (Vastus Lateralis) and hamstring (Biceps Femoris) muscles along with the PKD test. The activation of EMG during PKD can be understood in relationship to the flexion and extension of the lower leg. It is interesting that EMG activity for quadriceps is seen at every flexion cycle in the post stimulation data, while on the other hand EMG activity is nearly continuous in the initial cycles of PKD in the pre stimulation. This may be an indication of a change in the activation pattern of EMG from the agonist and antagonist muscles as a result of the vestibular stimulation, which is caused by neural changes in the vestibular descending signal. Preliminary studies done on subjects without disability comparing NASA jump test pre and post riding a rollercoaster indicate that there are significant differences in the knee and hip angles, which can be explained as a result of the change in muscle tone caused by the exposure to microgravity or cyclic gravity while being on rides. A preliminary study done on a 35 year old subject with CP, showed promising results in reducing spasticity after stimulating the vestibular system using the vestibular stimulation chair. Data from the Pendulum Knee Drop (PKD) test show a significant reduction in the knee stiffness (K), and virtual trajectory (θvt) that is noticed as a change in the shape of knee trajectory post stimulation when compared to pre stimulation. The final work presented in this study includes seven subjects with spasticity due to cerebral palsy. The PKD test, along with EMG, is used to assess their level of spasticity. Alterations to the vestibular descending signals while passing through the vestibular nuclei and going down toward the alpha motor neurons command a change in the muscle activation patterns that are responsible for setting the level of spasticity or muscle tone. Furthermore, this effect was found to be retained for at least 15 minutes post stimulation. One subject’s data is excluded from the study due to her high initial baseline measure of muscle tone and spasticity which is determined with the extreme firing of EMG bursts. In all the other six subjects of this study, the knee stiffness and damping parameters show a dramatic decrease post vestibular stimulation, and a smaller change is also noticed in the virtual trajectory (θvt) specifically in two subjects who have no dystonia. Four of the subjects have dystonic spasticity and the other three do not have dystonia along with spasticity. The vestibular stimulation effect is different between the two groups, and it is found that stimulation do not have the same effect on the level of dystonia as much as it do on spasticity. Subsequent analyses of EMG lead to a potential linkage between the EPH and the muscle reflexes (EMG). It is important to note that: 1) this work cannot be claimed as a permanent treatment for children with CP, but a combination of the described stimulation along with the proper physical therapy might have a very positive effect on the disorder. 2) Another path that can have a similar impact on the described population is by changing the stimulation duration intensity and providing the stimulation more frequently for at least five consecutive weeks might have a major impact on reducing the level of spasticity in children with CP

The Effect of Astym Treatment on Muscle Performance

Purpose: Astym treatment is a manual therapy intervention that stimulates tissue regeneration and treats pain, limited mobility, and muscle weakness associated with musculoskeletal pathology. The purpose of this study was to determine if Astym treatment administered to the lower extremity would result in an immediate change of maximal force output during a unilateral isometric squat test among individuals with a lower extremity injury. Methods: Forty-five subjects (14males; 31females) aged between 18-65 years participated in this study. The subjects were randomized into 3 treatment groups: 1) Control group - received no treatment 2) Placebo group - received a sham Astym treatment 3) Astym treatment group- received Astym treatment to the lower extremity. After familiarization to the operations of a computerized leg press machine, a baseline measure of maximal force output (pre-test) was determined by the average of 3 trials with a 30 second rest period between the trials. The subjects then received the designated treatment intervention. Immediately following the treatment intervention the subjects were retested (post-test) using identical testing procedures by an investigator who was blinded to the treatment intervention received by the subjects. The percent change of maximal force output from pre-test to post-test measures was compared using a one-way analysis of variance with alpha set at 0.05. A Tukey\u27s post-hoc analysis determined the statistical differences between the groups. Results: The treatment intervention had a significant effect on the percent change of maximal force output [F(2,42) = 7.91, p = 0.001]. Tukey\u27s post hoc analysis demonstrated that the percent change of maximal force output was significantly greater in the Astym group (15+18%change) compared to the placebo (-6+11%change) and control (-1+17%change) groups. No significant difference (p=0.68) was noted between the control and placebo groups. Conclusions: Astym treatment to the involved lower extremity increased maximum force output during an isometric squat test immediately following treatment. The results of this study suggest that Astym treatment can be used as an intervention for the immediate improvement of muscle performance for patients presenting with muscular weakness caused by a lower extremity musculoskeletal injury

Gait Variability and Kinematic Alterations in People with Diabetes Mellitus and Peripheral Neuropathy

Background: People with diabetes and peripheral neuropathy have been reported to show alterations in lower limb joint function compared to healthy non-diabetic people. Specifically the maximum angular movement available at certain joints can be reduced during static, non-weight bearing tasks. Limited joint range of motion has the potential to compromise balance and stability thereby increasing the risk of falling. It is unclear whether a reduction in the extent of movement available at the joints is reflected by a reduction in the amount of angular movement actually utilised during a functional task such as stair negotiation. The aim of this study was to determine if people with diabetes show reduced dynamic range of motion at the ankle, knee and hip joints during stair ascent and descent in comparison to controls. Falls risk during stair negotiation was calculated by measuring the degree of variability in dynamic joint range of motion. Methods: Data were generated from three groups: subjects with diabetes and peripheral neuropathy (DPN), diabetes without peripheral neuropathy (DM), and healthy controls (Ctl). The study was conducted in a gait laboratory using motion capture and related 3D software for analysis. Joint range of motion for the ankle, knee, and hip were captured during level walking, stair ascent, and descent. A seven step, bespoke staircase was fabricated for this purpose. Analysis of Variance (ANOVA) and Newman-Keuls tests were used to analyse the data. Results: Significantly reduced ankle range of motion, in the sagittal plane, was observed in the DPN group during stair ascent when compared to the controls. For stair descent, the DPN group demonstrated a significant increase in knee and hip ROM in the frontal plane, and also hip ROM in the transverse plane. No significant differences between the groups were identified for joint variability. Conclusions: People with DPN demonstrate alterations in dynamic range of motion at the lower limb joints during stair ascent and descent. The degree of angular movement utilised for both stair tasks was decreased at the ankle joint and this has the potential to undermine balance and stability. In contrast, angular movement at the knee and hip joints was increased in the frontal and transverse planes. This may compensate for impaired balance and stability by increasing the base of support to maintain balance and assist in foot clearance and placement. The specific combination of increased angular movement at the knee and hip may represent a compensatory stair gait strategy in response to reduced angular movement at the ankle joint

A review of the effectiveness of lower limb orthoses used in cerebral palsy

To produce this review, a systematic literature search was conducted for relevant articles published in the period between the date of the previous ISPO consensus conference report on cerebral palsy (1994) and April 2008. The search terms were 'cerebral and pals* (palsy, palsies), 'hemiplegia', 'diplegia', 'orthos*' (orthoses, orthosis) orthot* (orthotic, orthotics), brace or AFO

Aerospace medicine and biology: A continuing bibliography with indexes (supplement 297)

This bibliography lists 89 reports, articles and other documents introduced into the NASA scientific and technical information system in April, 1987