Biofeedback, positive and negative biofeedback, process, uses.

1. Biofeedback
Dr. Usha (PT)
Assistant Professor

2. CONTENTS
 Definition
 Purpose of biofeedback
 Selection of biofeedback
 Signals used clinically for biofeedback
 Principles of using biofeedback clinically
 Mechanism of biofeedback
 Uses of biofeedback
 Success in biofeedback
 Biofeedback equipment
 Advancement in biofeedback

3. DEFINITION
 The word “feedback” means ‘a method of
controlling the system by re- inserting into it the
result of its past performance.’
 Feedback can be positive where a change in one
direction causes further change in the same
direction, or it can be negative where in change in
one direction can causes further change in the
opposite direction.

4.  The positive feedback is generally the opposite to
what is required for homeostasis, for this reason
there are many negative feedback systems on the
body and only a few positive feedback systems.
 Most systems in the body that rely on negative
feedback systems to maintain homeostasis in the
body include: blood pressure, body temperature,
blood glucose levels, etc.
 Whereas an example of positive feedback system
is seen with childbirth.

5. NegativeFeedback

6. During childbirth uterine contractions
generate pressure on cervix
This causes release in hormone
oxytocin
Oxytocin causes more powerful
uterine contractions
This results in more oxytocin
release and so on.
PositiveFeedback

7. Definition of Biofeedback
 Biofeedback can be defined as the use of
instrumentation to make covert physiological
processes more overt; it also includes electronic
options for shaping appropriate responses.
 The use of biofeedback provides patients with
sensorimotor impairments with opportunities to
regain the ability to better assess different
physiological responses and possibly to learn self-
control of those responses.

8. PURPOSE OF FEEDBACK
 Extrinsic feedback is deliberately used in clinical
context to improve learning of a particular
behavior.
 The person may not be conscious of the actual
process they use (for eg. to recruit motor units or to
change the temperature of skin of an area of the
skin), the aim is to have them learn so that
eventually they can make those same changes
voluntarily, without having to use biofeedback
equipment.

9. SELECTION OF BIOFEEDBACK
 The art of effectively using the biofeedback
equipment lies in the fact of properly identifying
which equipment might be better used to elicit
which changes and using it to gradually shape the
development of the new behavior required.
 Here behavior means changes such as recruitment
of motor units from a muscle, etc.

10. Signals Used Clinically For Biofeedback
 The signals available are predominantly used
clinically for diagnosis or for monitoring
performance.
 Table- Types and source of signals used clinically
for biofeedback and monitoring

11. Source Signal Type Device Uses Include
Muscle Electrical EMG Monitoring & to increase or decrease
muscle activity
Brain Electrical EEG Monitoring & to change the prevalence
of some types of brain waves
Heart Electrical ECG Monitoring & to change the HR
Blood Pressure Pressure Sphygmomanomet
er
Monitoring & to change the reading
Local
Temperature
Temperature Thermometer Monitoring & to change local
temperature, e.g. hand
Blood Flow Flow rate Doppler flow meter Monitoring & to change local blood flow
volume, e.g. hands
Skin Changes in
conductivity
Galvanic skin
response
Monitoring & to change levels of anxiety
& distress
Joint Angle Relative position
of parts of a joint
Electrogoniometer Measuring & to change range of
movement used
Compression Pressure
dynamometer
Bulb
Sphygmomanomet
er
Measuring or increasing grip strength,
pelvic floor strength, muscle strength
Postural Sway Changes in
pressure
distribution (rate
& magnitude)
Force platform
connected to
appropriate visual
display
Monitoring & to improve balance

12. PRINCIPLES OF USING
BIOFEEDBACK CLINICALLY
1. Providing feedback
2. User control
3. Selection of starting position
4. Shaping behavior

13. 1. Providing feedback:
 There are two aspects for provision of feedback:
Appropriate for the change required.
Should be easily recognized and used by the
patient.
 Talking about the first aspect it says that:
 Changes in blood flow can be measured using a
Doppler flow meter or it can be measured indirectly
e.g. Local skin temperature measured with a
thermometer as an indicator of blood flow.

14.  The feedback should be proportional to response. Thus a
strong muscle contraction should produce a strong signal.
 This suggests that visual signals such as digital readout
can be better than auditory feedback. Because it is
easier to make direct comparisons within and between
trials and a digital readout provides a more sensitive
measure.
 The equipment used to provide feedback must be
sufficiently sensitive and specific. If not then risk is
changes in signals may be too small or unreliable to assist
the patient to learn what action on their part will change
the output.

15. So an integral part of the success in using
biofeedback is having the patient associate their
actions or changes in their body with a change
in the output signal. This requires appropriate
sensitive and specific feedback.

16.  Now talking about the second aspect of when selecting
appropriate biofeedback method is how feedback
should be provided so that it is easily recognized and
used by the patients.
 The usual methods are visual and auditory. This means
that the person might need to see the output reading of
a signal, as a number, a bar graph, or on a meter. If
auditory, the signal might be adapted to increase in
volume or pitch if there is an increased output and
decrease if the signal drops.

17.  The other most important consideration when
providing feedback is time i.e. the contiguity of the
signal and the patient receiving it as a feedback is very
important.
 If there is a delay say of 5 minutes the patient might
not associate the changes on the display with those
they perceive in response to their effort.
 Hence unless the signal is almost instantaneous, there
is a risk it will not be effective.

18. 2. User control:
 Biofeedback is controlled by the user.
 Once having learnt the ideas and how to use the
relevant equipment, the user does not usually need a
therapist to provide ongoing feedback related to
each performance of the selected task or activity.
Instead, appropriately chosen biofeedback
equipment can reliably indicate when performance
is improving, not changing or deteriorating.

19. 3. Selection of the starting position:
 It must be appropriate to the activity in which the person
can most easily achieve an approximation of the goal.
Hence it is the first stage shaping the last behavior that is
required.
 If relaxation is to be attempted then, to reduce general
muscle activity, the body must be fully supported lying or
half lying with the EMG readout visible or audible, as
required.
 The position selected should be such that the movement
goes unhindered and visible to the patient and also there is
little need for fixator or synergistic activity in other
muscles.

20.  For e.g. If activity of lower trapezius is to be increased
in relation to upper trapezius, the person should be
sitting comfortably on a stool, possibly facing a mirror
and able to hear (or see) the feedback.
 Now after the skin preparation and the electrode
placement ensure that the patient knows what
movement is required.
 This can be done by exaggerating the unwanted
movement to show what is to be avoided. According to
the above example it could be shoulder abduction with
the point of the shoulder leading.

21.  As the patient gains control over the movement the
starting position can be changed and made to standing.
As they manage it repeat it with a very small weight in
their hand.
 The progressions required to shape the behavior
depend on the aim of treatment and the rate at
which the patient attains them. The therapist’s
planning is important in the process of shaping
change.

22. 4. Shaping behavior:
 In the beginning the task may be approximate to the
actual goal. But as the patient is able consistently to
achieve the preset goals the therapist will have to rest
the threshold of performance required for success.
 The threshold that the user is to beat or not to exceed is
usually set.
 For eg. If the aim is to minimize muscle activity the
threshold is set so that the user will consistently be
able to keep their level of muscle activity below it.

23. Depending on the equipment this can be indicated by a
sound, as to when the level of activity is below the
preset threshold the sound stops, starting again when
or if the level of muscle activity increases.
 Conversely some equipment permits the user to have
the sound start once they have achieved the goal so
that its stopping indicates too high a level of tension
has again developed.

24.  Overtime the therapist will change what is required as
changes in behavior occur. This is what is called
shaping.
 It basically requires the therapist to select appropriate
equipment, set suitable goals within the user’s
capacity, and make adjustments in response to
changing behavior.

25. Mechanisms of Biofeedback
 It works by initially making the patient aware of his
or her own sensations when a dysfunction occurs
eg. Spasticity.
 The aim is that patient can consciously identify and
actively prevent what is happening.
 At last the response should be automatic and not
necessarily active or conscious at the part of the
patient. That the response can be conditioned.

26.  In many patients the control is gradually lost when the
immediate feedback is removed. In order to maintain
the control the feedback must be withdrawn from some
of the trials so that the patient gradually learns the
response with progressively fewer feedback
reinforcements.
 Successful outcomes occur in some and not all patients
and the success that does occur is often modest.

27.  Irrespective of the outcomes biofeedback is clearly
effective in one domain: i.e. It sets out to teach
patients control of their own body, be it a specific
movement or the level of relaxation.

28. Make the patient identify as to what is
happening when a dysfunction occurs
The patient learns to change his/ her response
accordingly using biofeedback
The biofeedback response is removed
progressively from the tasks so that the
patient learns the response
And hence the response
can be conditioned

29. USES OF BIOFEEDBACK
 Biofeedback is used for one of the two broad
purposes:
To increase activity or the level of output
To decrease activity or the level of output

30.  Biofeedback has is uses in:
Stroke
Spasticity
Recovering and improving muscle function
Chronic musculoskeletal injuries
Pain
Posture control
Balance and mobility

31. Trunk muscle re- education
Respiratory control
Incontinence
Stress related conditions
Hypertension
Raynaud’s disease

32. STROKE
 Studies relating to role of EMG following stroke
show different levels of effectiveness. It basically
suggest how clinicians might use biofeedback to
improve outcomes following stroke.
 Following stroke focus is mainly on:
Activation of wrist extensors
Shoulder abductors
Ankle dorsiflexors
Proper weight bearing

33.  The aim of using biofeedback is:
Either to increase the output or number of MUAP’s
in response to biofeedback output readings.
Or to decrease the output of selected muscles such
as those with increased tone like wrist flexors and the
calf.

34.  Treatment usually starts with the patient in
comfortable position with limb at rest and well
supported.
 As their control over the MUAP’s controlled by
muscle spasm increases, the aim is to keep the reading
low while perhaps, moving the contralateral limb, or
changing the position of the body.

35.  A review of 11 RCT’s that investigate the contribution
of EMG biofeedback on improving lower limb
function post stroke suggest that it does not have a
clear effect on gait training but it is used to strengthen
the ankle dorsiflexors, equalize weight distribution
over both limbs during sit to stand or to prevent knee
hyperextension during walking. Also it affects the
factors affecting mobility.

36.  Similarly EMG biofeedback is also used to treat upper
limb problems for post stroke patients.
 In a RCT considering effect of placebo EMG and EMG
biofeedback to wrist extensors show that patients in both
the groups improved with the treatment.
 The difference in functional improvement between those
having real and those having sham EMG was not
statistically significant but at the same time, the EMG
surface potentials and the active wrist extension improved
more for those patients treated with EMG biofeedback than
those treated with sham EMG biofeedback.

37.  The extent of weight bearing on each leg can also be
monitored and used as biofeedback. Any type of
pressure sensitive shoe insert can be used with
appropriate signal processing circuitry.
 For this therapist needs to set the level of compression
(body weight) necessary to stop a sound or to make a
sound as the preset level (goal) is attained.
 Alternately this can be used to limit the amount of
weight bearing on a lower limb- if a certain level is
exceeded a noise can be preset to warn the patient to
change how they are weight bearing.

38.  So we can say that studies can be useful in improving
some sequelae of a stroke.
 But while using biofeedback besides therapist needing
to ensure an appropriate method and type of feedback
is used there are clearly other issues such as patient
preference that affects the treatment.
 If the person does not wish to use biofeedback or is
unable to use it be it because of stroke then methods
of treatment that rely less on patient’s active
participation must be used rather than using
biofeedback where patients act as their own therapist.

39. SPASTICITY
 In spasticity EMG biofeedback is used to retrain
dorsiflexor function to improve gait in CP
children.
 3 therapists conducted EMG biofeedback sessions
for 6 weeks and a daily home programme increased
active and passive ranges of dorsiflexion and in
some subjects rate of foot tapping and the strength
of the muscles.
 Hence by this EMG provides a guide though as to
how biofeedback can be used to produce change in
the presence of spasticity.

40. Recovering and Improving Muscle
Function
 Biofeedback is used to improve outcomes of range
of problems that affect voluntary muscle
contraction such as following nerve injury, after a
nerve or a tendon transplant and to increase the
strength.
Following peripheral nerve injury when once
motor unit activity has been detected with an EMG,
voluntary repetition can be encouraged along with
verbal encouragement by the therapist.

41.  Biofeedback equipment can provide sufficient
feedback to encourage an increase in activity and
number of practice sessions.
For long standing facial muscle paresis a study was
done that compared a group of patients who were
taught with a mirror (visual feedback) and another
group who was taught with EMG feedback. There
was no significant difference in two groups preferably
because both are forms of biofeedback (mirror being
low technology).

42. In case of nerve transplant biofeedback can be used
to help the patient to learn the new muscle action.
Similarly after trauma to muscle or its attachment or
after tendon muscle transplant EMG may make it
possible for the patient to perform a particular
voluntary movement.

43.  If some minimal voluntary movement is possible, a
biofeedback type intervention is of benefit.
 And if no voluntary movement is possible a combination
of electrical stimulation and biofeedback may be
beneficial.
Muscle strengthening and endurance training devices
in clinical facilities and gymnasia have electronic displays
which indicate strength or power developed. These can be
included in biofeedback devices as the subject can at a
predetermined rate, thus learning to maintain a
particular training schedule. They can also use their
previous target as a measure to be exceeded.

44. Chronic Musculoskeletal Injuries
 EMG can be used to treat musculoskeletal injuries
produced by repetitive or cumulative trauma.
Repetitive trauma suggest that the person has an
ongoing need to repeat the movements that are
producing pain or pain producing pathology.
 The possibility of using biofeedback in such
instances is to decrease the level of activity in
specific muscles (for eg. activity of trapezius
during shoulder and neck pain). This can be learnt
by watching EMG output on a visual display unit.

45. Pain
 EMG has been found to be effective in treating
intractable rectal pain which is because of
paradoxical increase in pubo rectalis muscle
activity.
 In this an intra rectal EMG electrode can provide
feedback enabling patients to learn the sensations
associated with effectively relaxing the muscle.
Methods such as visualization and range of
relaxation techniques can also be used along with
EMG.

46.  Chronic musculoskeletal pain produces reduction in
joint movement and associated muscle tightness. EMG
biofeedback has been used to produce muscle
relaxation to enable stretching when patients have
chronic musculoskeletal pain.
 A study conducted on 30 patients of patello-femoral
pain syndrome was done. The patients were divided
into experimental and the control group. The
experimental group was given conventional exercise
therapy and conventional biofeedback and the control
group was given the exercise therapy only.

47.  The results indicate that those who were given EMG
biofeedback developed a greater increase in the level
of electrical activity in vastus medialis. This suggests
that EMG can be a more effective treatment in
instances where conventional exercise therapies alone
are used at restoring muscle activity in presence of
pain that is sufficient to reduce function.

48. Posture Control
 For postural control, monitors are worn to signal tilt
away from vertical. An inclination monitor is
worn at the trunk and the head position trainer is
worn as a helmet.
 As the trunk or head is moved from the vertical a
receiver worn on the belt vibrates or produces
sound.
 Normal movement is possible and there is no
reduction in the muscle activity.

49. Balance and Mobility
 Force plates are used to provide feedback related
to the aspects of balance and mobility.
 The type of feedback provided ranges from simple
sounds if a preset level of perturbation occurs to
complex visual screen displays.
 It may be used during activity like reaching out to
touch an object or it may be during single or double
leg stance and aimed at minimizing the extent of
postural sway movements.

50. Trunk Muscle Re-education
 For trunk muscle re education pressure
biofeedback is used. This is mostly used when
exercising the deep abdominals and posterior spinal
muscles to treat or prevent low back ache.
 The patient is required to maintain a level of
pressure in the unit for duration of a contraction.
This type of unit comprises of an inflatable air
filled bag with one or more chambers with a
sphygmomanometer like pressure gauge attached.

51.  The unit is placed between the patient and a hard
surface and the patient is required to keep the unit
compressed by contracting the deep abdominals- if in
prone it can be done by increasing the posterior pelvic
tilt by “drawing in” the relevant abdominal muscles
without breath holding.
 Another way of developing postural control is by using
feedback from a diagnostic ultrasound unit. The
ultrasound unit is used to provide an image of the
relevant muscle group (like transverse abdominus,
multifidus or pelvic floor).

52.  As the person contracts the real time ultrasound
permits them to “see” their deep muscles changing
size. With practice it becomes to increase control
without always requiring to see the ultrasound image.

53. Respiratory Control
 Here biofeedback is used in weaning off the
patients from respirators.
 According to a study biofeedback can help reduce
the neural parameters that drive respiration by
providing audible feedback to indicate the patient
when the level of EMG activity of their third
intercostal muscles rose above the initial resting
level while they were rebreathing some CO₂.

54. Incontinence
 Biofeedback is used for retraining both fecal and urinary
incontinence.
 With fecal incontinence a pressure biofeedback device or EMG
biofeedback is used.
 The pressure biofeedback device requires the use of rectal balloon.
The balloon is used either to teach the patients to identify a
sensation of rectal stimulation and contract their external anal
sphincter.
 EMG biofeedback uses an intra anal sensor or surface electrodes to
teach effective use of anal sphincter.
 For urinary incontinence typically intra vaginal electrodes are used.

55. Stress Related Conditions
 The use of biofeedback for relaxation for relaxation
is the use of a galvanic skin response sensor with
computer input.
 The ultimate aim is to teach the patients method of
stress reduction.
 We can make the patient play an outcome related
game. If the level of patient’s relaxation decrease
their progress through a game can be reversed until
they again achieve sufficient level of relaxation.

56. Hypertension
 Blood pressure readings can be used as extrinsic
biofeedback.
 For this a study was conducted with 30 men with
mild un medicated essential hypertension (SBP=
140- 200mmHg and DBP= 90- 115 mmHg).
 Biofeedback was followed by home sessions using
a purpose designed finger pressure cuff. The result
was clinically significant reduction in BP after 4
weeks and an increased ability of biofeedback
trained group to lower SBP on demand.

57. Raynaud’s Disease
 The primary symptom of raynaud’s disease is vaso
spastic attacks, the feedback used is thermal
changes (an indirect measure of blood flow to
area).
 People with raynaud’s disease have difficulty to
control their skin temperature.

58. Success in Biofeedback
 Success in biofeedback depends on:
Quality of biofeedback training,
 Skills of trainer,
 Success in early sessions are important for a
successful outcome.

59. Biofeedback Equipment
 Biofeedback equipment has three essential
components:
Transducer
Signal processor
Visual or audible display
Transducer: It detects physiological variable such
as blood flow, heart rate, EMG activity, or skin
temperature and produces a corresponding signal
(often electrical signal) which changes with change
in physiological variable.

60. Signal processor: It may amplify, filter and/or average the signal
and convert it to a useful form- one which can be displayed or
communicated to the patient.
 Some equipments are relatively simple such as simplest form of
biofeedback requires only a glass thermometer which a patient
can see.
 The liquid in the bulb of thermometer (mercury or alcohol) acts
as a transducer and expands in proportion to the temperature.
The “signal” is processed by thin glass tube- the mercury or
alcohol level in the tube is proportional to the expansion of the
liquid. A visual display is created by labelling the tube so that
the fluid height in the tube indicates the temperature.

61.  Digital thermometers use a thermistor as the
transducer.
 When a voltage is applied to a thermistor, the amount
of current flow depends on the temperature of the
thermistor.
 The measured current flow is converted to a
corresponding temperature value and shown on a
digital display or simple analogue meter.

62. EMG equipment:
 EMG equipment used for diagnostic purposes,
research and biofeedback are different in their
qualities.
 EMG used for biofeedback equipment are usually
considerably cheaper, less sensitive and with a
different range of options.
 EMG designed for electro diagnosis and research use
a wide range of electrodes- from fine wire or needle
electrodes to surface electrodes.

63. Here a transducer may be surface
mounted electrodes or needle electrodes.
Both detect an electrical signal which is processed
(amplified and filtered then averaged and smoothed).
And the finally resulting signal is
displayed and sometimes also recorded.

64. New technology propels the application of
diverse biofeedback therapy options within the
context of functional training to improve motor
control among neuro rehabilitation patients.
Advancement in
Biofeedback

65. Thank you