The Many Dimensions of Pain
Pain is very personal and subjective. Science no longer views pain as a sensation
, but sees it rather as an experience that results from a
conglomerate of physical, psychological, emotional and social inputs. As
a fitness professional, you have no doubt trained or taught clients and
participants who were dealing with the effects of pain. You yourself may
have a relationship with pain that has affected your life and career.
The International Association for the Study of Pain (2014) defines pain
as “an unpleasant and emotional experience associated with actual or
potential tissue damage, or described in terms of such damage.” The word
“potential” is significant in this definition because it signifies that
pain can be experienced even in the absence of tissue damage. According
to the American Academy of Pain Medicine (2015), pain affects more
people in the United States (an estimated 100 million) than diabetes,
heart disease and cancer combined.
Pain is generally defined as acute or chronic. As an indicator of the
state of the tissue or imminent danger to the organism, acute pain is
a valuable evolutionary characteristic that alerts us to take action
(withdraw, rest or avoid). This initial information is a result of a
noxious stimulus (mechanical, thermal or chemical) detected by our nociceptors
, sensory neurons that respond to potentially damaging stimuli by
sending signals to the spinal cord and brain (Garland 2012).
There is currently no universally accepted definition for chronic
pain , but experts generally agree that it persists beyond the time
in which tissue would normally heal (typically 12 weeks/3 months)
(Merskey & Bogduk 1994). Some authors also define pain as chronic if it
recurs for 6 months or more (Falla et al. 2014). Chronic pain in later
life is a worldwide problem.
In one nationwide survey of older adults ( n = 7,601) in the
United States, 52.8% reported experiencing bothersome pain in the
preceding month (NIH 2015).
As a fitness professional, you are highly likely to work with clients
who have chronic and/or recurring pain. These clients need to be cleared
for exercise by their physician. When they come to you, they will
probably have completed or be currently involved with treatment from a
licensed medical provider such as a physical therapist or chiropractor.
You must remain within your scope of practice at all times and avoid any
attempts to treat or diagnose pathological conditions or to provide
medical advice.
The Bio-Psycho-Social Paradigm
Understanding the many events that contribute to the pain
experience—what Canadian psychologist Ronald Melzack (2001) calls the neuromatrix
—will help you design safe and productive programs and environments
for your clients. The neuromatrix is an aspect of the bio-psycho-social
(BPS) model of modern pain science that researchers and clinicians have
structured to better understand and treat chronic pain.
-
“Bio” represents biology or biomedical interventions, the way chronic
pain has historically been treated—by purely seeking disease,
dysfunction or damage and designing interventions that find and “fix”
it. -
“Pyscho” denotes the current psychological characteristics of the
person who is suffering from chronic pain. These characteristics
include the individual’s beliefs about the situation; historical
references related to past pain experiences; anxiety and/or
depression; and expectations about the future. -
“Social” refers to the social implications of the pain experience.
Social stressors relate to an absence of support and the sufferer’s
feelings that peers, friends and family don’t believe the pain is
real. Additional stressors may include missing important social
events, being unable to travel and having to withdraw from employment.
The growing body of evidence regarding pain science is changing the way
medical professionals approach treatment. To best assist clients who are
experiencing chronic pain, you need to understand the bio-psycho-social
paradigm and what that means in relation to program design,
communication and expectations. The following research roundup explores
this
paradigm from different angles and offers important take-
home
messages.
Pain Research
Visual References
Chronic pain is complex, resulting from many inputs processed through
the nervous system and the brain. Visual references are one type of
input the brain relies on to determine a potential threat to the
organism. For example, a bruise may not hurt until you notice it is
there.
For those suffering from chronic neck pain, vision provides a great deal
of feedback about cervical range of motion. The endpoint a person sees
when turning his or her head and experiencing pain combines with a
cluster of other information occurring at the same time to form the
neuro-representation of the pain experience in the brain, or what
Melzack (2001) calls a “neuro-signature.”
To investigate the role of visual feedback on neck pain, Harvie et al.
(2015) used a virtual-reality apparatus to alter the visual
proprioceptive feedback that subjects received during cervical rotation.
Subjects were seated with their torsos fixed to avoid contributing
motion from the thoracic spine during cervical rotation. Twenty-four
subjects with chronic neck pain were assessed for the onset of pain
during cervical rotation to the left and right. They were asked to stop
when they felt pain and to rate it on a scale of 0–10 at the point in
the rotation where pain occurred. Each subjects was then fitted with a
virtual-reality headset that provided six different visual scenes for
six trials.
Researchers manipulated the virtual-reality scenes so that the visual
cues did not match the actual cervical-rotation distance that subjects
achieved on all trials. The virtual rotation provided by the headsets
was either 20% more than the actual rotation, the same as the actual
rotation or 20% less than the actual rotation. The bogus visual feedback
of plus or minus 20% made the subjects perceive that they were rotating
their cervical spines 20% more or less than they actually were.
The results showed that when rotation was understated (subjects
perceived their rotation was less than it actually was), pain-free range
of motion increased by 6%. When rotation was overstated (subjects
perceived their rotation was more than it actually was), pain-free range
of motion decreased by 7%.
Take-Home Message
This study provides additional evidence to support the findings that
pain is not generated solely from tissue damage. Vision is one of many
inputs that the brain processes when assessing a threat to the body, and
vision therefore contributes to the production of pain. The association
of a specific neck range of motion identified visually, coupled with
information from the motor system and proprioceptive system, creates a
confirmed reference for past pain experiences.
It is plausible that visual input can also influence pain in other
areas. For example, if a client has lower-back pain, forward flexion of
the spine will bring her eyes closer to the floor, possibly presenting a
painful or pain-free experience, depending on the client. When designing
a program for such a client, you could vary the visual field to minimize
the visual association related to painful movements. One suggestion:
Have the client visually follow her hand out to the side of the body by
rotating the head as she flexes the spine.
Pain Anticipation
In a study of 20 healthy undergraduate students, researchers (Vanden
Bulcke et al. 2013) investigated whether the anticipation of a
painful stimulus made subjects more aware of an innocuous tactile
stimulation to a body part compared with no anticipation of pain. In an
elaborate experimental setup, the students placed both forearms on a
table and their hands were fitted with instrumentation that measured
tactile sensitivity, an instrument that delivered innocuous tactile
stimuli and an instrument that delivered painful electrocutaneous
stimuli. A video monitor informed the subjects immediately prior to each
trial if a painful stimulus would possibly be delivered.
The stimuli were delivered to both hands at irregular intervals. In the
threat trials, a colored warning designated a specific hand and alerted
the students to the possibility of a painful stimulus (on the designated
hand only); sometimes that painful stimulus actually followed, and
sometimes it did not (it was the innocuous tactile stimulus instead).
During the control trials, a color alerted the subjects that a specific
hand would be affected, but the signal indicated (accurately) that no
painful stimulus would be administered, only the tactile stimulus.
Each hand received one of the two stimuli in every trial, with an actual
painful stimulus delivered to one hand 10% of the time. Subjects were
required to report which hand felt the stimulus first each time. Results
showed that when pain was expected, innocuous tactile stimuli were
perceived sooner on the threatened hand than they were on the “neutral”
hand. These findings demonstrate that the anticipation of
pain resulted in the prioritization of somatosensory sensations at the
location of possible threat. This would indicate that the brain was
biased toward the threatened body part.
Take-Home Message
It’s common for someone who is dealing with chronic pain to be
hypervigilant or overprotective of the affected area. However, this
often leads to increased sensitivity and perceptions of threat from
innocuous or neutral sensations. For example, a client may expect that a
simple or safe exercise or movement will be damaging because he feels
sensations in the protected region of the body. This may negatively
affect functional outcomes at work, at home or in the gym. Acknowledge
and validate a client’s concerns when they arise in instances such as
this. Modify exercises or even substitute a move until the client can be
gradually and safely exposed to the movement or similar movements.
The Relationship Between Diagnostic Imaging and Pain
Do degenerative changes automatically lead to pain? Guermazi et al.
(2012) used magnetic resonance imaging (MRI) to look for osteoarthritic
(OA) changes in knees. Radiographic imaging (X-rays) of the same knees
showed no pathology. OA is generally diagnosed through examination and
X-ray. X-rays can identify bony changes to the joint but can’t identify
soft-tissue pathologies. Using the more sensitive MRI would make it
possible to detect structural lesions associated with OA and its
relationship to age, sex and obesity. The subjects were 50 or older
(mean age 62.3 years). Out of the 710 subjects, 206 (29%) complained
about knee pain.
Overall, 631 (89%) of the subjects showed some knee abnormality. The
three most common findings were osteophytes, cartilage damage and bone
marrow lesions. These abnormalities increased with age. The study
concluded that 91% of those who had knee pain also had abnormal MRIs,
leaving 9% of those with painful knees with normal MRIs. Eighty-eight
percent of those with no knee pain showed abnormalities in the MRIs. The
authors noted that those with the most abnormalities identified as
having mild pain, not moderate or severe pain.
Another study, published in the European Spine Journal (Kato et
al. 2012), looked at the cervical spine MRIs of 1,211 asymptomatic
volunteers. The subjects were Japanese men and women equally
representing each decade of life from the 20s to the 70s. All of the
subjects had an MRI and underwent a neurological exam administered by a
spinal surgeon. > >
The findings showed spinal cord compression, spinal cord signal changes
and disk compression. Increased signals on an MRI are associated with
abnormal tissue, such as scarring or inflammation. For a disk bulge to
be considered pathological it had to measure more than 1 millimeter from
the vertebral body.
Of the 1,211 asymptomatic subjects studied, 64 (5.3%) showed spinal cord
compression. High-intensity signal changes were seen in 28 (2.3%)
subjects, and 1,061 (87.6%) presented with bulging disks. The prevalence
of symptoms was significantly higher in people over 40 years of age.
Take-Home Message
Degenerative changes to the body are a normal part of aging and do not
directly correlate with pain. The studies clearly demonstrate that an
individual can have many abnormal findings in the neck and knees and yet
have no pain. Clients who have had imaging studies done may experience
stress or fear when learning of abnormalities in joints or soft tissue.
If imaging reveals degenerative changes, medical professionals often
consider these changes to be the sole source of the clients’ pain—and
clients who have experienced pain in the past may themselves perceive
this to be the case, even if they are not currently in pain.
A client who believes that known degenerative changes will lead to pain
may act with self-limiting and guarded movements, in an effort to
anticipate pain. This has the potential to decrease the client’s
functional capacity and increase her anxiety about certain exercises or
activities. Work closely with allied medical professionals to ensure
that your program design will not provoke any symptoms, and help the
client feel more confident that abnormal findings may not necessarily
lead to the experience of pain. Also keep in mind that physicians may be
overcautious when giving advice; for example, they may say, “Do not
squat,” when this is an action we do every day. Help the client discern
the difference between an activity that is truly contraindicated and one
that is not.
Exercise and Pain
The American Pain Society and the American College of Physicians (Chou &
Huffman 2007) endorse exercise as a treatment intervention for chronic
lower-back pain (LBP). Many in the fitness community, the medical
profession and the general public believe that core training (including
core strength and/or core stability) is the solution for LBP.
Wang et al. (2012) performed a meta-analysis (a statistical technique
for combining results from independent studies) on the effectiveness of
core stability exercise versus general exercise. They looked at five
studies that included 414 patients and compared core stability to
general exercise for LBP. The subjects all had chronic LBP ( > 3 months).
The results of the analysis showed that core stability exercise was
better than general exercise for short-term pain relief. However, in
long-term follow-ups at 6 and 12 months, there was no difference between
core stability exercise and general exercise. The analysis also showed
that in the short term, functional status improved with core stability
exercises.
The authors acknowledged some limitations associated with this
meta-analysis, noting that the results were based on relatively
low-quality data with a high risk of bias. For example, neither the
subjects nor the clinicians were blinded to the interventions or the
outcomes. The total number of subjects (414) was too small to enable
researchers to identify differences between the two exercise
interventions. And the types of core stability exercises were not
specified, nor were examples provided.
In a study by Falla et al. (2014) the authors looked not at an exercise
intervention but rather at relevant muscular responses to the exercise
environment. The study examined the lumbar erector activity of patients
with chronic LBP versus healthy controls. Multiple prior studies had
shown that people with chronic LBP displayed biomechanical disturbances
in trunk, spinal and lumbopelvic motion.
Using electromyography (EMG), Falla and colleagues observed muscle
activity during a repetitive lifting task of 25 cycles in 200 seconds.
The load lifted was consistent for all subjects, and researchers
controlled the rate of movement with a metronome. They measured pain
thresholds while lifting and 3 minutes after the test and then compared
those numbers with baseline pain levels for the LBP subjects.
Results showed that healthy controls used a more variable movement
strategy and changed the distribution of lumbar erector activity during
the repetitive lifting task. This muscle activation variability in
different regions of the erector spinae in healthy subjects may be a
preferential movement strategy for maintaining motor output and avoiding
overload on one region. Conversely, the LBP group performed the task
with the same group of lumbar erectors throughout the task. This lack of
variability and muscle activity coincided with reduced lumbar movement
and higher levels of LBP. The LBP group also showed a reduction in mean
EMG frequency. Over time, a reduction in EMG frequency can occur due to
an accumulation of metabolic byproducts, which may then lead to
increased nociception stimulation and fatigue.
Take-Home Message
When selecting exercises for clients who have chronic pain, be specific
and consider the entire bio-psycho-social perspective. Some
clients—particularly those who report back instability—may respond well
to core stability exercises. But others may already be overusing a
bracing/stability strategy that is counterproductive to long-term
function and movement confidence. For a client in this group, isometric
core stabilization exercises such as planks may reinforce the lack of
variable motion in the lower-back region and perpetuate the
limited-movement strategy that has been shown to increase their pain.
For this client, consider beginning with more remedial corrective
exercises in postures or positions that do not immediately encourage
bracing; for example, exercises that are done prone, supine, in
quadruped position, kneeling or half-kneeling. Help the client focus on
external cues to remove his attention from his internal focus on
stabilizing.
Movement variability is key to healthy motion and dissipates mechanical
stress to soft tissue and joint structures, thereby avoiding localized
fatigue and developing alternative movement strategies.
The Complexity of Pain
We can no longer view chronic pain as purely the result of biological
origins. The current body of science has identified many factors that
contribute to the human pain experience. Information from the peripheral
and central nervous systems and cognitive functions all play a part in
how a person experiences pain.
Pain is a complex issue, and it is neither helpful nor accurate to
approach client communication and programming from an outdated paradigm
that solely addresses the physical or somatic effects of pain. Broaden
your awareness of the bio-psycho-social model and have a professional
support system in place to help clients reach their pain-free movement
goals.