Journal of Rehabilitation Medicine 51-1CompleteIssue | Page 19

lowered TA activity in SW (p = 0.041) compared with
walking without an AFO. No effects are found in the
other sub-phases of gait (p = 0.398, 0.696 and 0.407
for DS1, SS and DS2, respectively).
DISCUSSION
C. Nikamp et al.
16
This study shows that AFO use after stroke decreases
TA muscle activity during swing within a single measu-
rement session, without negatively affecting TA muscle
activity over 26 weeks.
The results comparing TA muscle activity with and
without AFO are in accordance with our hypothesis
and in agreement with previous studies comparing
the effects of AFOs in the swing-phase during a single
measurement session (5–7).
Based on the results of previous studies assessing
the effects of AFO use only at a certain point in time,
AFO use was suggested to decrease the activation
of muscles around the ankle, thereby encouraging
disuse of these muscles (3, 5, 6). Consequently,
AFO use was thought to worsen the existing loss of
strength and possibly delay recovery (8), resulting in
permanent gait impairments and AFO dependence
(6). To our best knowledge, the present study is the
first to assess the long-term effects of AFO use after
stroke. No changes were found in AUC of the TA in
swing during the follow-up period of 26 weeks while
walking without AFO, for subjects either in the early
or delayed group. Significant changes in AUC in SS
were found for the delayed group. Post-hoc analysis
revealed that AUC at T3 differed significantly from
T1 and T2, showing higher levels at T3. We have no
explanation for this increase at T3. Significant changes
were also found in DS2, but post-hoc analysis did not
reveal any significant differences between individual
measurements. The results for the swing phase did not
show any negative effects of long-term AFO use on TA
muscle activity post-stroke. This is in accordance with
a study by Geboers et al., which included patients with
peripheral paresis (8). They found reduced activity of
ankle-dorsiflexors with AFO within a single measure-
ment session, but 6 weeks of AFO use did not lead to
a general lower level of EMG activity. To explain our
results, studies suggest that the possible negative ef-
fects of AFOs on muscle activity in a single gait cycle
might be counteracted by the fact that AFOs improve
walking in general (6, 8). An increase in amount of
walking (steps taken) is suggested to offset a decrease
in EMG during a single step (6).
Ideally, one would need a long-term longitudinal
randomized controlled trial, including a control group
with no AFO use to determine whether long-term use
of AFOs affects TA muscle activity after stroke. How­
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ever, this is not feasible for ethical reasons. Instead,
groups were provided with an AFO early or delayed
after stroke, which was found not to influence results.
We already reported positive effects of AFO provision
on ankle kinematics early after stroke (17), while no
effects of early vs delayed AFO provision on pelvis, hip
and knee kinematics were found after 26 weeks (18).
At the same time, beneficial effects of AFO provision
were found on functional levels (12). After 26 weeks
no differences with respect to balance and mobility
were found between early and delayed provision, but
early provision showed favourable outcomes in the first
11–13 weeks, possibly resulting in earlier independent
and safe walking (19). For clinical practice, this means
that clinicians, together with the patient, can decide
when to start AFO treatment based on personal priori-
ties and preferences. Early AFO provision is expected
to provide beneficial effects on a functional level in
the short-term, without negatively affecting muscle
activity of the TA in the long-term.
An important strength of the study is that this is the
first to measure the effects of AFOs on muscle activity
of the TA in a longitudinal study-design post-stroke.
Furthermore, subjects were included early (within
6 weeks) after stroke, both with independent and
dependent walking ability at the start of the study.
Thereby, our study conditions match with the situa-
tion in which clinicians often consider AFOs in daily
clinical practice.
Study limitations
This study has some limitations. First, the sample
size was relatively small, and this was limited further
at T1, since not all subjects were able to perform this
measurement at that time. Secondly, the longitudinal
design included 4 separate EMG measurements during
the 26-weeks follow-up period. Changes in electrode-
position may arise and could affect results. This was
limited, since a standard protocol was used to define
electrode positioning (15). Changes in measurement
conditions are inevitable in a longitudinal design
including subjects early after stroke. This includes
changes in the use of walking aids and shoes during the
follow-up period. Although we tried to limit variation
as much as possible, changes in walking aids and shoes
between measurements could have affected our results
(20). The results may also be affected by the use of
different types of AFOs in our study. However, because
of the small sample size, a sub-group analysis per type
of AFO was not possible. Furthermore, walking speed
increased during the study, which is known to affect
EMG (16). Therefore, walking speed was included as
confounder in the mixed-model analyses. Post-hoc