Influence of attention on patterns of coordination during gait in patients with chronic low back pain

People with chronic low back pain often have a characteristic gait pattern that
differs from unaffected controls, such as slower speed and less flexibel
coordination between thorax and pelvis. This 'abnormal' gait could be caused by
the continuous presence of pain, which demands a lot of attention. This in turn
leads to behavior patterns aimed at reducing or preventing pain, such as
avoiding certain situations and walking at a slower pace. From earlier research
we know that the level of pain can be temporarily reduced by diverting
attention away from pain. In this research we study what happens to the gait
pattern when attention is incluenced. On the one hand, we expect that the
quality of walking will improve when attention is drawn away from the pain. On
the other hand, we expect the quality of walking to deteriorate even further
when attention is directed toward pain.
Attention will be manipulated with the Stroop task. Subjects are shown words
printed in different colors, and subjects have to name aloud the color, and at
the same time ignore the meaning of the word. From experimental psychology we
know that the word meaning is subconsciously processed after all, and that
subjects take more time to name the color of words that are somehow emotionally
relevant. In this study we make use of a so called dual task paradigm, wherein
we combine a walking activity with the attention task. In one condition,
subjects will walk on a tread mill and simultaneously name the colors of so
called incongruent Stroop words, such as the word 'RED' shown in blue ink. The
words are shown on a screen in front of the subjects. We expect that the
attentional cost of this task will temporarily divert attention away from the
pain, which will show itself in slightly improved walking, e.g. faster, and
more flexible. In another condition, subjects are shown Stroop words that
symbolise motor activities that are presumed to be 'threatening' to subjects
with chronic low back pain, such as 'LIFTING', or 'BENDING'. It is expected
that when subjects perform this Stroop task, attention is directed toward the
pain, and walking will slightly deteriorate (slower, more rigid).
If our hypothesis is correct, this will provide strong evidence for the role of
attention in pain related behavior. If, on the other hand, no effects of our
manipulation are found, this will imply that attention plays a weaker role in
coordination than has been hitherto assumed. We hope that these results can
eventually be used to improve rehabilitation of people with chronic low back
pain.

What happens to the gait pattern of low back pain patients when attention is
manipulated?
If these patients perform an attention demanding task during walking will this
results in a temporary improvement in the quality of walking, such as larger
steps and improved coordination between thorax and pelvis?
Will attention be negatively affected if subjects are in general fearful, and
/or suffer from a form of kinesiophobia?

Subjects (patients & controls) walk on a treadmill, whilst performing a
cognitive dual task. Light reflecting markers that are placed on pelvic,
trunk, and feet. Movement of the markers are tracked with 3 video camera's
(SIMI) placed next to the treadmill.
Stimuli are projected on a screen.
There are 4 experimental conditions: ) walking without dual task (= baseline),
2) walking while naming the colors of squares, 3) walking while naming the
colors of incongruent Stroop words (e.g., the word BLUE shown in a red font),
4) walking while naming the colors of movement Stroop words.
Prior to the walking task all Stroop test are performed seated (reference).
Subjects complete the following questionnaires: a) the TAMPA scale for
kinesiophobia, b) the Pain Catastrophing Scale, and (c) the Beck Depression
Inventory. After the experimental trials patients rate to what extent they
expect (or think) that the activities of the Movement Stroop test would lead to
pain when actually performed.

Manipulation of attention (Stroop-task)

De risico*s voor de proefpersonen zijn te vergelijken met het risico van
normaal lopen, terwijl een andere taak wordt uitgevoerd die aandacht vergt (bv.
lopen en telefoneren). Het risico van vallen is opgevangen door middel van een
veiligheidsgordel die is bevestigd aan het plafond. Aan weerszijden van de
lopende band is een reling. Bovendien is er een noodknop aanwezig waarmee de
band door de proefpersoon of de proefleider kan worden stopgezet. Daarnaast zal
altijd een proefleider naast de lopende band staan om de proefpersoon
nauwlettend in de gaten te houden en waar nodig in te grijpen.


The level of risk for subjects is comparable to the risk of normal walking and
performing another task (e.g. walking an talking to a cell phone). The risk of
falling is minimised by a safety belt attacted to the ceiling. The treadmill is
flanked on both sides by a hand rail. In case of an emergency the experimentor
can shut down the tread mill immediately. The entire procedure will be closely
monitored by an experimenter who can take necessary actions.