EMG biofeedback effectiveness to alter
muscle activity pattern and scapular kinematics in subjects with and without
shoulder impingement
muscle activity pattern and scapular kinematics in subjects with and without
shoulder impingement
Huang HY, Lin JJ, Guo YL, Wang
WT, Chen YJ. J Electromyogr Kinesiol.
2012 Oct 31. pii: S1050-6411(12)00167-8. doi: 10.1016/j.jelekin.2012.09.007.
[Epub ahead of print]
WT, Chen YJ. J Electromyogr Kinesiol.
2012 Oct 31. pii: S1050-6411(12)00167-8. doi: 10.1016/j.jelekin.2012.09.007.
[Epub ahead of print]
Recently, clinicians have
focused on reinstituting normal scapular motion to rehabilitate patients with
subacromial impingement syndrome (SAIS) since abnormal scapular motions
contribute to pain and dysfunction. These
abnormal scapular motions may be caused by altered neuromuscular control; for
example, the upper trapezius may be more active while the lower trapezius and
serratus anterior are inhibited. This
imbalance is often difficult to treat and must begin with muscle
reeducation. Therefore, the objective of
this study was to determine if biofeedback improves scapular motion and
neuromuscular control (based on muscle activation ratios: upper
trapezius/middle trapezius, upper trapezius/lower trapezius, upper
trapezius/serratus anterior) in 12 healthy participants and 13 participants with
SAIS. Participants were hooked up to a
3D kinematic system (to measure scapular motion) and electromyography to measure
muscle activation in four scapular muscles (upper, middle, and lower trapezius
and the serratus anterior). Participants
first performed shoulder abduction in the scapular plane to record scapular
kinematics. Participants then performed
three exercises without and then with biofeedback (side-lying external rotation,
forward flexion, and knee push-up). The
authors found that biofeedback improved all three muscle activation ratios during
the forward-flexion exercise in both groups.
When the healthy group performed the side-lying external rotation
exercise with biofeedback their upper-to-lower trapezius ratio improved compared
to not using biofeedback during the exercise. However, when the participants
with SAIS did this exercise with biofeedback their upper-to-middle trapezius and
upper trapezius-to-serratus anterior ratios improved compared to not using
biofeedback during the exercise. Biofeedback
did not influence neuromuscular control during the knee push-up exercise. For scapular kinematics, participants with
SAIS had more posterior tipping of the scapula with the use of biofeedback
during shoulder abduction.
focused on reinstituting normal scapular motion to rehabilitate patients with
subacromial impingement syndrome (SAIS) since abnormal scapular motions
contribute to pain and dysfunction. These
abnormal scapular motions may be caused by altered neuromuscular control; for
example, the upper trapezius may be more active while the lower trapezius and
serratus anterior are inhibited. This
imbalance is often difficult to treat and must begin with muscle
reeducation. Therefore, the objective of
this study was to determine if biofeedback improves scapular motion and
neuromuscular control (based on muscle activation ratios: upper
trapezius/middle trapezius, upper trapezius/lower trapezius, upper
trapezius/serratus anterior) in 12 healthy participants and 13 participants with
SAIS. Participants were hooked up to a
3D kinematic system (to measure scapular motion) and electromyography to measure
muscle activation in four scapular muscles (upper, middle, and lower trapezius
and the serratus anterior). Participants
first performed shoulder abduction in the scapular plane to record scapular
kinematics. Participants then performed
three exercises without and then with biofeedback (side-lying external rotation,
forward flexion, and knee push-up). The
authors found that biofeedback improved all three muscle activation ratios during
the forward-flexion exercise in both groups.
When the healthy group performed the side-lying external rotation
exercise with biofeedback their upper-to-lower trapezius ratio improved compared
to not using biofeedback during the exercise. However, when the participants
with SAIS did this exercise with biofeedback their upper-to-middle trapezius and
upper trapezius-to-serratus anterior ratios improved compared to not using
biofeedback during the exercise. Biofeedback
did not influence neuromuscular control during the knee push-up exercise. For scapular kinematics, participants with
SAIS had more posterior tipping of the scapula with the use of biofeedback
during shoulder abduction.
Rehabilitation of scapular
musculature in patients with SAIS is often very challenging due to muscle
inhibition and altered firing patterns.
This study demonstrated that biofeedback may improve muscle activation ratios,
which is an indicator of neuromuscular control.
Commonly the upper trapezius is over active and because of its size and
strength it can easily alter the scapular upward rotation force couple thereby
causing a scapular shrug rather than smooth coordinated upward rotation. Biofeedback can be used to allow the patient
to figure out how to decrease activity of the upper trapezius and increase
their lower trapezius and serratus anterior activity. Therefore, this modality would be very
beneficial during the initial stages of rehabilitation to reeducate and improve
neuromuscular control. This study
utilized a visual form of biofeedback that allowed the participant to see the
live muscle activity; however, there are many other forms of biofeedback that
can be used. Another form of visual
feedback is the use of mirrors so that the patient can observe the motion of
the scapula and relate it to their voluntary activation. Auditory feedback is another alternative that
uses a beeping sound that increases in frequency with a stronger contraction of
a specific muscle. Proprioceptive
feedback can also be used in terms of scapular tape or bracing to enhance
neuromuscular activation. Based on these
results visual biofeedback is an easy way to improve muscle activity ratios in
patients with SAIS. Future clinical
trials should evaluate if improving muscle activity ratios improves patient-reported
outcomes. Do you use any form of biofeedback
with your SAIS patients or even for other injuries? What forms of biofeedback do you use or find
effective?
musculature in patients with SAIS is often very challenging due to muscle
inhibition and altered firing patterns.
This study demonstrated that biofeedback may improve muscle activation ratios,
which is an indicator of neuromuscular control.
Commonly the upper trapezius is over active and because of its size and
strength it can easily alter the scapular upward rotation force couple thereby
causing a scapular shrug rather than smooth coordinated upward rotation. Biofeedback can be used to allow the patient
to figure out how to decrease activity of the upper trapezius and increase
their lower trapezius and serratus anterior activity. Therefore, this modality would be very
beneficial during the initial stages of rehabilitation to reeducate and improve
neuromuscular control. This study
utilized a visual form of biofeedback that allowed the participant to see the
live muscle activity; however, there are many other forms of biofeedback that
can be used. Another form of visual
feedback is the use of mirrors so that the patient can observe the motion of
the scapula and relate it to their voluntary activation. Auditory feedback is another alternative that
uses a beeping sound that increases in frequency with a stronger contraction of
a specific muscle. Proprioceptive
feedback can also be used in terms of scapular tape or bracing to enhance
neuromuscular activation. Based on these
results visual biofeedback is an easy way to improve muscle activity ratios in
patients with SAIS. Future clinical
trials should evaluate if improving muscle activity ratios improves patient-reported
outcomes. Do you use any form of biofeedback
with your SAIS patients or even for other injuries? What forms of biofeedback do you use or find
effective?
Written by: Stephen Thomas
Reviewed by: Jeffrey Driban
Related Posts:
Huang HY, Lin JJ, Guo YL, Wang WT, & Chen YJ (2012). EMG biofeedback effectiveness to alter muscle activity pattern and scapular kinematics in subjects with and without shoulder impingement. Journal of Electromyography and Kinesiology PMID: 23123099
I think the idea behind this particular study is great. I feel EMG bio-feedback can be a great tool when utilized correctly during rehabilitation. In our clinical setting it is often used following surgical procedures, most commonly for quadriceps activation following ACL reconstruction. I would be curious if it can be useful to treat patients with shoulder impingement. It makes since that through visual and/or audio feedback, along with proper exercise, improper shoulder and scapular kinematics and firing patterns can be targeted. The results of this study are promising, however I do have some reservations.
It did not state whether the EMG and non-EMG exercises were randomized. The procedural flow chart showed "exercises with EMG biofeedback" occurring after "exercises without EMG biofeedback". I wonder if this could have any effect on the results. I'd be curious to see future studies look at the long-term effects of EMG-biofeedback training.
I agree with Aaron. The results of this study are promising and correlate with what I have seen in clinical practice. When beginning rehabilitation for scapular dyskinesis it is imperative that the patient is performing the exercises correctly. Most of the time, these patients have no idea what the exercises should look and feel like. I have not used EMG biofeedback but I have used proprioceptive feedback and visual feedback to help the patients see and feel the correct way to perform an exercise and have seen great results. Knowing the short-term versus long-term effects of EMG-biofeedback or biofeedback in general would be very helpful, therefore future research should be targeted towards that.
Aaron: You bring up an interesting point. I don't think you could randomize the order of biofeedback or no-biofeedback exercises b/c if the biofeedback is effective then it might have lasting effects on the EMG signal. An interesting design might be to have a randomized study where one group does the exercises without biofeedback twice and another group does it once without and once with biofeedback. The first group would help us figure out if it's a learning effect that accounts for the altered EMG signals. In the end, I think we'll need to see a clinical trial to confirm if the biofeedback and altering the muscle activation ratios really matter in the long run.
I think it would also be interesting to see if the effects of using the EMG Biofeedback last after the biofeedback treatment is discontinued. If they tested the ratios of muscles working in these shoulder movements after a month post-treatment, would the ratios still be more equal or would the patient revert back to using more of their upper trapezius?
Thanks everyone for the comments! I agree with everything being discussed. Clearly more research is required especially to examine the long term effects of biofeedback. It is very encouraging to see the scientific results matching up with our own anecdotal data. I do feel much more than one session of biofeedback is required to have lasting effects. Also the athlete might regain proper firing with isolated movements but during more gross/functional motions they revert back to their old/bad habits. I think we need to help them transition from isolated to functional with the use of biofeedback before returning to play or work. What are others thoughts?