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Jon Newman -> Re: LB exercise vs. general physical activity (November 29, 2005 4:37:00 PM)
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Here's a bit from the full text, addressing limitations and strengths.
[QUOTE] Several limitations of this study should be
considered when interpreting our findings.
Our participants were primary care patients
taking part in an investigation of treatment
options for low back pain. Thus, they may
not be representative of individuals with low
back pain who present for care in other kinds
of clinical settings (e.g., specialty clinics or
centers focusing on third party liability or
workers' compensation cases) or who do not
seek clinical treatment at all. Because all of the participants had low back pain at baseline,
we cannot draw inferences about the associations
of exercise and physical activity
with pain or disability and psychological distress in initially pain-free populations. Also,
because the outcomes assessed here are relatively
common, the odds ratios observed
probably tended to overestimate reductions in
relative risks. Furthermore, information on
specific types of back exercises was not collected.
Although little evidence indicating that
some specific exercise regimens are more effective
than others exists in the literature, certain
exercise regimens may be more effective
than others. Also, we relied on participants'
self-reports of their exercise and physical activities,
and it was not feasible to validate responses
with other strategies such as direct
observation.
Because recreational physical activity was
not randomized, confounding is an additional
concern, although we considered the most important
potential confounders in our analytic
strategy. Residual confounding is possible,
however. For example, individuals with more
chronic or disabling histories of back pain
may be more likely than those with less severe
or chronic histories to engage in regular
back exercise. Although we controlled statistically
for baseline duration of low back pain
episode and number of previous episodes of
pain, our back exercise estimates could still
be subject to residual confounding. However,
it is unlikely that such confounding would be
so substantial as to mask truly protective back
exercise effects.
Although these limitations weaken our ability
to offer firm causal inferences, our study
involved a number of strengths that support
the possibility that the associations observed
may in fact be causal. First, the 18-month follow-
up rate of almost 90% diminishes the
possibility that our findings were due entirely
to selection bias. Second, we controlled for
several factors likely to confound crude associations
of exercise and physical activity with
subsequent pain, disability, and psychological
distress. Third, previously validated measures
were used in assessing all outcomes, and well established
MET values were assigned to
physical activity categories. Finally, because
our serial assessments involved a large population
of low back pain sufferers, we were
able to conduct analyses that clearly delineated
the temporal relations of exposures and
outcomes. The stronger cross-sectional than
longitudinal associations observed suggest
possible reverse causation, a problem inherent
in interpreting estimates derived from
cross-sectional studies of physicai activity and
low back pain.
In summary, in a population of primary
care patients presenting with low back pain,
participation in recreational physical activities
was inversely associated, both cross-sectionally
and longitudinally, with low
back pain, related disability, and psychological
distress. In contrast, back exercise was
positively associated both cross-sectionally
and longitudinally with low back pain and
related disability. These results suggest that
individuals with low back pain, rather than
being advised to engage in specific back exercises,
should instead be encouraged to
focus on nonspecific physical activities to
help reduce their pain and improve their
psychological health. Because of the perception
that physical activity could result in
pain persisting for a longer period and fear
of pain have been identified as possible factors
keeping low back pain patients from
being physically active, clinicians may
want to reduce such barriers to patients
modifying their behavior [/QUOTE]jon
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