Biofeedback & RealTime Motion Capture
Biofeedback
– What are the possibilities?
With the release of The MotionMonitor xGen, our inaugural blog
shared some of the things you have been telling us regarding the state of
motion capture software. Biofeedback and
its use to understand human movement was one topic with lots of interest. In this blog we will explore the topic and
user applications in more detail.
What is
biofeedback?
A typical definition of Biofeedback is “a treatment in which patients learn to control
bodily processes that are normally involuntary such as muscle tension, blood
pressure, or heart rate.” In
today’s world of research this definition is way too narrow. The common view probably, flows from early
use of surface electromyography (sEMG) to treat
disorders ranging from tension headache to joint dysfunction. A more appropriate and generalized definition
might be: “Biofeedback is a process in which any raw or processed data derived
from human movement, or initiation of movement, is provided to the subject in a
control feedback loop with the purpose of modifying that movement through a
process of learning.”
With this broader definition the
concept of “biofeedback” can use more data to analyze and modify behavior in a
wide array of areas that range from performance enhancement in sports to injury
reduction in ergonomics to rehabilitation of musculoskeletal injuries and to
the rehab and study of motor control systems.
Steven
Lavender,PhD at The Ohio State University, in a NIOSH grant proposal that was designed
to modify the lifting behavior of manual material handlers, drew on Learning
Theory and existing research to explain elements that are necessary for
biofeedback to be effective. He noted
that complex motor skills are best learned when experienced rather than
demonstrated; include "transitional cues" associated with
modification of the behavior; and provide knowledge of results in the form of objective
data to determine if a positive behavioral change has occurred. In his case, the transitional cues were an
auditory signal whose pitch was a function of the moment being generated on the
L5/S1 joint. Not your typical
biofeedback signal!
Biofeedback clearly
has possibilities well beyond that narrow definition.
How is
Biofeedback Being Used?
So, how is biofeedback being used in the context of this broader
definition and what are the types of feedback being provided as transitional
cues? One example is from the field of ergonomics.
If, as Steve Lavender suggests,
“transitional cues” are important for modifying complex motor skills, visual
cues alone may actually hinder learning. In this ergonomic application designed to
reduce shoulder elevation, an auditory signal indicating “out of bounds” would be more useful as an alert for the subject to immediately “feel” the danger
zone. The visual “stop and go” while
useful to the coach, is too distracting for the subject.
Rehabilitation is another area that benefits from a broader
definition of biofeedback. Ricardo
Matias of Setubal Polytechnic Institute, in an article “Effectiveness of Three-Dimensional Kinematic Biofeedback on the Performance
of Scapula-focused Exercises” (https://comum.rcaap.pt/handle/10400.26/7051)
demonstrated that the use of kinematic feedback was more effective in modifying
behavior than sEMG based feedback during certain shoulder motions. Essentially, his research showed that sEMG,
while useful in getting subjects to activate particular muscles, did not
necessarily result in the desired change of scapular motion. However, by using kinematic data as feedback,
subjects not only modified their movement but also activated the correct muscle
combination.
James Thomas, PT, PhD and Peter Pidcoe,
PT, PhD at Virginia Commonwealth University are analyzing “how real” virtual
reality has to be in order to engage the subject. In their virtual Dodge Ball game which encourages
people with back pain to move, they have added tactile feedback in the form of
vibrators to provide feedback to body segments that have been “hit” by the
opposing team. In this example, visual
interaction, reward systems and tactile feedback are providing a deeper level
of feedback and a more real virtual world.
Biofeedback has been widely used in motor control. It has been used both as a rehabilitation tool in the case of stroke and as a tool to better understand motor control systems. For example, reaching into an immersive display of virtual objects allows the subject to observe their hand movement in a virtual environment that cannot be reproduced in the real world.
Using error augmentation and a representation of the hand with an immersive display, James Patton, PhD at Rehab Institute of Chicago, displayed a perturbated representation of the hand which induces the subject to overcompensate as part of stroke rehabilitation protocol. Using a similar display, Jill Campbell Stewart, PhD writing in Experimental Brain Research (https://link.springer.com/article/10.1007/s00221-014-4025-7) observed repeated reaches to random targets to discern the level of planning and compensatory adjustments undertaken by stroke patients.
Another application where visuals can be useful is during training.
Using biofeedback with therapists as they learn manual therapy mobilization
techniques is one example. In this excerpt from a demo video, various visual representations can be used to monitor the amount of force that the therapist is
applying. Here a slip graph and bar graph are being used
to ensure force is reaching the targeted level.
Of course, there are many other examples of biofeedback applications and research such as gait retraining, augmenting running mechanics, movement sonification and more. We encourage you to write to us at support@TheMotionMonitor.com or in the comments below with your suggestions & questions for biofeedback applications.
What is
necessary for biofeedback software to be effective?
For software to be effective as a
biofeedback tool there are two important considerations. The first is speed of processing and latency
in the display of feedback. Measurement
rates and software architecture
are extremely important for biofeedback.
Processing speed must be sufficiently fast to eliminate latency between
action and feedback for the training to be beneficial. At the same time, the underlying collection
rate has to be fast enough to satisfy Nyquist if the data were to be valid. We discussed these issues in some detail in
our 7/24/2018 blog on Real Time Collection of Biomechanical Data (https://www.themotionmonitorblogteam.com/2018/07/real-time-motion-capture-in-biomechanics.html) and should be reviewed carefully
before investing in a biofeedback system.
The second consideration is the User Interface and ease with which
biofeedback exercises can be constructed.
Subject deficiencies and the variety of research studies suggest that
the user must be able to set up exercises quickly. When investigating systems for use in
biofeedback, this is arguably one of the most important issues. If one is required to program or write
exercises using Visual Basic or other programming languages, the setup time and
limited interface will interfere with the successful use of biofeedback.
We'd welcome the opportunity to talk with you about your applications & experiences with biofeedback. Feel free to use the comments section below or send us an email at support@TheMotionMonitor.com.
-Ian
We'd welcome the opportunity to talk with you about your applications & experiences with biofeedback. Feel free to use the comments section below or send us an email at support@TheMotionMonitor.com.
-Ian