Exercise Training and 6MWD
Despite an increase in 6MWD following exercise
training of 36 8 37 m in the exercise group (p ! 0.01) and
6 8 38 m (p = 0.54) in the control group, the difference
in magnitude of increase between the groups did not
reach statistical significance. This is most likely a consequence
of large variability in 6MWD between individuals,
and a relatively small sample size. All subjects had a
high 6MWD at baseline, potentially resulting in a ceiling
effect for the 6MWT in this group of individuals. It is
possible that an alternative exercise test not constrained
by gait speed may be more appropriate in this group. The
minimal important difference in 6MWD following pulmonary
rehabilitation in COPD subjects has been reported
to be 54 m based on a between-subject comparison
[26] , and more recently an analysis of data from seven trials
found that a change of 35 m represented an important
effect [34] . To date, no study has determined the threshold
value for an important change in 6MWD in middleaged
and older subjects with asthma.