Showing posts with label surface emg. Show all posts
Surface EMG | Exercise and Muscle Fatigue
Electromyography (EMG) has long been the clinical and research standard for skeletal muscle activity. Through manipulations of waveforms produced by electrical signals given off by muscle movement, researchers can gain insight into the mechanical properties of the muscular system. In exercise physiology, surface EMG is often used to study effort and usage dynamics of human muscles in an exercise setting. In a recent study by Jenkins et al, researchers observed the activity of the biceps and forearm during dumbbell curls between two groups. One group performed repetitions of curls with lighter weight (relative to their own 1- repetition maximum), and the other used heavier weight, both to the point of failure. The main difference here is that an exercise with a lighter weight can generally be repeated many more times than a heavier weight per set. There are differing views in the fitness community as to whether lifting heavier weights for fewer reps or lighter weights for many reps is more effective for optimal muscle activation. The researchers used a BIOPAC differential EMG amplifier and an MP150 system, combined with AcqKnowledge software to record data. The study shows, as a result of the surface EMG recordings, that there are significant differences in muscle activity in response to these differing methods of training. The total exercise volume, as a product of the weight lifted and reps performed, was similar between groups. However, a noticeable rise in EMG amplitude was recorded in those who performed more reps with light weights, suggesting greater muscle fatigue and activation in these individuals. These results conflict with previous studies performed with leg extensor resistance training, in which more muscle activation was observed in the heavier weight group. Thus the paper concludes that differences in muscle structure and blood flow may alter the effectiveness of different training methods across different muscle groups.Surface EMG | Musician’s Cramp
Focal hand dystonia, also known as “musician’s cramp,” is a movement disorder that causes involuntary flexing in the fingers, or finger cramps, when playing a musical instrument. This disorder poses a huge problem for professional musicians and in some cases can even threaten their careers. Many methods have been attempted to try and alleviate the ailment, but the most effective training method has been the “slow-down exercise” (SDE). This exercise, based on the fact that symptoms disappear when playing at a slow tempo, involves selecting a short passage that triggers the cramps then slowing the tempo down to where the musician can play without involuntary finger flexing. The same passage is then repeated over and over, gradually increasing the speed over time. While this method has helped improve symptoms, it was unclear what aspects of motor skills improved through SDE training.
Michiko Yoshie, Naotaka Sakai, Tatsuyuki Ohtsuki and Kazutoshi Kudo investigated how SDE affected motor performance, muscular activity, and somatosensation in a dystonic pianist. The study entitled “Slow-Down Exercise Reverses Sensorimotor Reorganization in Focal Hand Dystonia: A Case Study of a Pianist” tested a musician over a 12 month period as she underwent SDE training for 30 minutes a day, playing a specific passage that evoked the finger cramps most substantially. During the motor task, the musician’s surface EMG was recorded using EMG amplifiers and a BIOPAC MP Data Acquisition System. Throughout the rehabilitation process the musician improved her speed of key strokes and actually helped recover her normal motor and somatosensory functions. The researchers even found evidence that showed the brain had the capacity to reverse sensorimotor reorganization that was induced by the focal hand dystonia. The findings objectively show that SDE training not only improves effected people’s key strokes but helps to completely recover from the neurological disorder.
Wireless Surface EMG Modules | Data Acquisition
Physiological
data acquisition systems offer many options for recording surface EMG, needle
EMG, and fine wire EMG. General muscle activity and fatigue can be determined
by recording and analyzing surface EMG data from major muscle groups.
Correlate
EMG activity with data from other sources including force plates, goniometers,
and motion analysis equipment. Analysis software
tools, including spike counting, muscle activation location, and frequency
analysis allow for post-acquisition surface EMG data interpretation. Results of
EMG recordings can be output as graph channels for easy data visualization, or
can be in numerical format in summary tables or spreadsheets. Data can then be
used for further statistical analysis.
EMG Analysis | Biomechanics
Biomechanics
research has never been easier thanks to powerful new data acquisition and
analysis tools. Perform real-time calculations and post-data acquisition
analysis on a variety of biomechanical and physiological data.
Simultaneously
acquire up to 16 channels of biomechanics and/or gait-specific data. An example
setup could incorporate two channels of heel/toe
strike timing, ten channels of EMG signals, and
four channels of goniometry data — however combinations are virtually endless.
Record sit-and-reach tests, range of motion evaluations, muscle balance
assessments and more.
Real-time
event markers allow researchers to log important events in the data and also
include comments that can be written during or post acquisition.
After
recording, choose an automated
analysis package to interpret and score the biomechanics data. For example,
automated EMG
analysis allows for a variety of automated functions including deriving
integrated EMG, root mean square (RMS) EMG, locating muscle activation, full
frequency and power analysis, and much more.
Muscular Biofeedback | Surface EMG
Biofeedback
is
a form of self-regulation in which an individual is provided information in the
form of sensory feedback about a biological condition or function in order to
gain control over that biological function. Biofeedback is often used as a
therapeutic tool by which sports medicine/rehabilitation professionals,
neurophysiologists, psychophysiologists, and therapists can use
electrophysiological instrumentation to measure, process, and “feedback” the
recorded information to the participating athlete or subject. The feedback is
usually provided through auditory and/or visual means.
There
are many types of biofeedback modalities available. One of the most popular and
widely accepted modalities is surface
EMG biofeedback. EMG (electromyography) bioinstrumentation measures
muscle activity by recording electrochemical activity of a muscle occurring
during depolarization and recruitment of a skeletal muscle motor unit. This
modality is used for muscle
reeducation and control when
orthopedic injuries or surgeries have taken place, or when the peripheral
nervous system has been impaired. It is also used to promote muscle relaxation
to decrease muscle guarding, pain, stress, and anxiety.
A
simple muscular biofeedback experiment design might use surface EMG electrodes
placed over the Vastus Medialis and Vastus Lateralis muscles. Surface EMG
electrodes should be placed vertically (parallel to the muscle fibers), over the
muscle belly, or largest part of the muscle, and a ground electrode should also
be used. Surface EMG should be recorded in several trials, including a Baseline
without biofeedback (where the participant is asked to maximally relax, e.g.,
not contract), Maximal Contraction
without Biofeedback, and a variety of Maximal Contraction with Biofeedback, such as
visual stimulus or auditory stimulus. After recording, compare the
surface EMG recordings and use peak-peak and mean measurements to determine if
any significant change was detected between any of the variables.
Biofeedback
is considered advantageous, as it provides participants a chance to use their
visual and auditory senses to become more aware of how they are performing
during therapy or training, attempt to improve upon it, and immediately see the
improvement as it is occurring. Because participants can immediately note
improvements, they are “rewarded.” This reward will hopefully lead to larger
improvements and accomplishments.
The Body Electric | Surface EMG
Electricity
is part of everything the body does.
Surface EMG electrodes noninvasively record the electrical activity of skeletal
muscles. The unit of measure for the electrical activity is the volt, which is named after Count
Alessandro Volta (who also invented the battery). The detection, amplification,
and recording of changes in skin voltage produced by underlying skeletal muscle
contraction is called electromyography;
the recording thus obtained is called an electromyogram (EMG).
Electricity
is always flowing in the body; it flows from negatively charged parts of the
body to positively charged parts. As this electricity flows, surface EMG (sEMG)
electrodes can detect and monitor the electrical activity.
Surface EMG electrodes noninvasively record the electrical activity of skeletal
muscles. The unit of measure for the electrical activity is the volt, which is named after Count
Alessandro Volta (who also invented the battery). The detection, amplification,
and recording of changes in skin voltage produced by underlying skeletal muscle
contraction is called electromyography;
the recording thus obtained is called an electromyogram (EMG).
Skeletal
muscles are stimulated to contract by somatic motor nerves that carry signals
in the form of nerve impulses from the brain or spinal cord to the skeletal
muscles. Although a single motor neuron can innervate several muscle fibers,
each muscle fiber is innervated by only one motor neuron. The combination of a
single motor neuron and all of the muscle fibers it controls is called a motor
unit. When a somatic motor neuron is activated, all of the muscle fibers it
innervates respond to the neuron’s impulses by generating their own electrical
signals that lead to contraction of the activated muscle fibers.
Integrated EMG “averages out” noise spikes in the raw EMG
data to provide a more accurate indication of the EMG output level
Muscle activation,
strength, fatigue, or twitch can be
monitored with surface EMG electrodes from a variety of body locations
to study Gait, Range of Motion, Isometric and Isotonic Contraction, Ergonomics,
startle response, etc. sEMG data can be
combined with other data to display muscle response simultaneously with other
physiological events.