The Effects of Pain and the Memory of Pain on Autonomic and Neuromuscular Function

Study Design This study will utilize a repeated measures quasi-experimental case control
design structure. Subjects will be placed into two groupings, those who have a history of
prior lower extremity injury and those who have no history of lower extremity injury. The
two groupings will be age and gender matched. Subjects who have no prior history of lower
extremity injury will be matched to subjects with a prior history of injury. There will be
an equivalent number of participants per group with similar demographic information in both
groups in order to reduce the number of variables influencing the results of the experiment.
Within each of these groupings, specific interventions will be clustered and performed as a
set. These clusters of interventions will be randomized to minimize internal testing error.
Both groups of participants will be exposed to the same interventions (baseline, pain
pressure, visualization of pain pressure and prior injury, and mental challenge test).
Investigators responsible for testing and outcome measurement will be blinded to the
groupings of subjects (past history or no prior history of injury). It is anticipated that
the testing, including initial set up, will take between 60 and 75 minutes. All testing
will take place at the Mount St. Mary's College physical therapy exercise and research lab
or in a private room at Knight Physical Therapy Inc.

Study Methods Initial Set Up (25 minutes) Upon commencement of the study, subjects will be
asked to fill out the Tampa Kinesiophobia Questionnaire, Fear Avoidance Belief
Questionnaire, Fear of Pain Scale, Pain Catastrophizing Scale, and the Vividness of Visual
Imagery Questionnaire. This should take approximately 10 minutes. Following completion of
these questionnaires, they will be introduced to the investigators and then asked to lie
supine upon the treatment table. A pillow will be placed under their head for comfort.
Surface EMG rRecording electrodes will be placed upon the belly of the tibialis anterior
muscle. An electrode will be placed upon the medial tibia and will serve as a ground for
the other two electrodes. Placement of electrodes will correspond to the side of injury
(i.e. prior injury to the right ankle would result in electrode placement on the right
tibialis anterior and right anterior deltoid muscles). In subjects without history of
injury, side of electrode placement will be predetermined and randomized. Also at this
time, subjects with a prior history of injury will be asked to identify the location of the
injury. The tester will then palpate the area of previous injury and will locate the tender
point in this area. This point will be marked with a pen for later use. In subjects with
no prior injury, the anterior talofibular ligament, the lateral knee joint line, or the
lateral belly of the gastrocnemius muscle will be located and marked on the side of testing.
The site will be randomized so as to blind testers. Testers will be informed of the side
to be tested through the sealed envelope that is opened prior to testing. They will be
blinded as to prior injury grouping.

At this point, the subject will be walked through the procedure and an initial pain pressure
threshold measurement will be taken and a simulated break test (see below for description of
break test) will be performed at the foot / ankle in order to familiarize the subject with
the test procedures and also to ensure that all equipment is functioning optimally. This
process should take approximately 10 minutes.

Following this procedure, a timer will be set and the subject will rest in this position for
five minutes to acclimate to the environment and to normalize their autonomic system.

Autonomic System Response (10 minutes) Following the five-minute acclimation period, heart
rate variability (HRV) data will be recorded, marked, and used as a baseline measurement.
The HRV data will be collected throughout each testing procedure. Initially, at the site of
previous injury (or randomized pressure site for subjects with no prior history of injury),
the tester will use their thumb to apply pressure to the site. The pressure will increase
until the subject reports their maximal pain level. Prior to the application of pressure,
the subject will be informed that they are to experience the maximum pain tolerable and to
inform the tester when that level is reached. The subject will next be instructed to notify
the testers when they have reached the maximum tolerable pain. Once achieve, the pressure
will be maintained for 10 seconds in order to get a baseline HRV recording. After 10
seconds, the pressure will be released and the HRV recording will be marked. At this time,
the subject will be asked to report their level of pain on a scale of 1 to 10. The subject
will then rest for three minutes to return their HRV to baseline values. At this point, the
subject will be instructed to close their eyes and imagine the pain pressure in their leg
that was just applied. HRV and pain values will be marked and recorded. The subject will
rest for another three minutes and then they will once again be asked to close their eyes.
In this instance, they will be asked to visualize the details of their prior injury. In
subjects with no prior injury, they will asked to visualize the muscles, bone, and blood
flow of their tibia. Like before, HRV and pain values will be marked and recorded.
Following another three minute rest period, the subject will be asked to complete a mental
challenge test. This test will require subjects to count backwards as quickly as possible
from 100 by 7. HRV and pain values will be marked and recorded. With this test, and with
all testing, the subject will be allowed to withdrawal from the test for any reason and
without repercussions.

Pressure Pain Threshold (10 minutes) The amount of pain and the force required to elicit the
pain response will be applied and monitored by a Wagner Force Ten™ FDX Digital Force Gauge
Pain Algometer. The algometer is a device designed to measure sensitiveness to pressure and
in pain studies; the algometer is used to measure sensitiveness to pain as a product of
pressure. The Wagner Force Ten Digital Algometer is a portable unit with a small 1
cm2-rubberized tip capable of applying pressures up to 50 lbs./ft. The unit is capable of
remembering multiple data points and storing peak force and force-averaged data that will be
retrieved after testing for later analysis. During each of the five test components
(Baseline, Pain Pressure, Visualization of Pain Pressure, Visualization of Prior Injury, and
Mental Challenge Test) the testing procedures will be identical to those applied earlier,
except instead of measuring muscle performance or HRV, pain pressure will be recorded. The
tip of the pain algometer will be placed upon the site of prior injury or upon the anterior
talofibular ligament. Pressure will be applied through the algometer and the subject will
be instructed to inform the tester when they first begin to experience pain. This value
will be recorded along with HRV values.

Neuromuscular Response (15 minutes) During the next phase of testing, a small rolled up
towel will be placed under the test ankle. The towel will be utilized to raise the foot
from the table in order to facilitate testing. At this point, the tester will stabilize the
lower extremity by grasping the calf approximately 12 inches above the malleolus. This hand
will provide a counter force to the forces applied by the test hand. In the test hand, a
Hoggan Scientific Microfet 2TM Handheld Muscle Tester will be placed upon the lateral aspect
of the fifth metatarsal bone of the foot. The placement will be proximal on the metatarsal
approximately at the base of the fifth metatarsal bone. The position of the sensor will be
marked to standardize test position and measured for later force measurement purposes. The
subject will be instructed to isometrically resist the force applied by the tester. At this
point, Surface EMG and Force recording will commence simultaneously. The Surface EMG will
be utilized to measure action potential propagation. Surface recording electrodes are
placed upon the skin to measure these action potentials. At no time will needles be
utilized to collect data and therefore, no penetration of the skin is required. The
initiation of the test will also be noted on the HRV recording. A steady but increasing
amount of force will be applied slowly and gradually to the foot in a medially and slightly
caudal direction until the subject can no longer resist the force. This process is called
the "break test" because the muscle is tested until it can no longer resist the force. The
subject will rest for 30 seconds after which the break test and associated data recordings
will be repeated two more times with a 30-second rest period in between tests.

The subject will be allowed to rest for three minutes prior to beginning the next portion of
the study. HRV testing will be started and then the tester as previously described will
place pain pressure upon the site of previous injury. The location of this site has been
previous marked for consistency of application. In subjects with no prior history of
injury, the pressure will be applied to the anterior talofibular ligament. When pain
pressure has reached it's maximal levels, a second tester will perform a break test on the
subject. Following the test, the subject will rest for 30 seconds and the process will be
repeated two more times with a 30 second rest period in between tests. Force, EMG, HRV, and
pain values will be recorded during each of the break tests.

Following a three minute rest period, the subject will asked to visualize the pain pressure
placed upon the leg (or visualize their tibia as previously described) and three break tests
will be performed during the visualization process. Force, EMG, HRV, and pain values will
be recorded during each of the break tests. This process will be repeated for visualization
of prior injury and for the mental challenge test.

Inclusion Criteria:

- Individuals who have experienced a significant injury in the lower extremity (i.e.
fracture, ligament strain, surgery, trauma) that resulted in a significant loss of
function for greater then three weeks time period will be included in the study.

- Significant loss of function will be defined as not being able to walk or being
required to use crutches for the three weeks and trauma shall be defined as physical,
emotional, or social distress or suffering that also coincided with injury to the
lower extremity.

- Individuals with a history of significant injury to the lower extremity will be age
and gender matched with individuals who have no history of traumatic injury.

Exclusion Criteria:

- Acute injuries in the lower extremity occurring less than six weeks prior,

- any heart conditions, any open wounds in their lower extremities,

- severe hypertension greater than 180/110,

- poor sensation in the lower extremities, or

- cognitive impairments that prevent following the instructions of the study, and

- chronic pain greater then 3/10 in any region of the body.