TITLE: Effect of Ankle-foot Orthosis on Lower Limb Muscle Activities and Static
Balance of Stroke Patients Authors’ Names

  ABSTRACT:
 [Purpose] This study examined the effects of an ankle-foot orthosis worn during balance
training on lower limb muscle activity and static balance of chronic stroke patients.
[Subjects] The subjects were twenty-five inpatients receiving physical therapy for chronic
stroke. [Methods] The chronic stroke patients were divided into two groups: thirteen
patients were assigned to the ankle-foot orthosis group, while the remaining twelve
patients wore only their shoes. Each group performed balance training for 20 minutes,
twice per day, 5 days per week, for 6 weeks. The lower limb muscle activities of the
paralyzed side tibialis anterior, medial gastrocnemius, and the stability index were
measured before and after the 6-week intervention. [Results] Comparison of the groups
indicated a significant difference in the muscle activity of the paralyzed side tibialis
anterior and the stability index of the eyes-open standing position. After the
intervention, the ankle-foot orthosis group evidenced a significant difference in the
muscle activities of the paralyzed side tibialis anterior and paralyzed side medial
gastrocnemius as well as the stability index of the eyes-open standing position,
eyes-closed standing position, eyes-open standing position on a sponge, and eyes-closed
standing position on a sponge. The group that only wore their shoes showed significant
differences in the stability indexes of eyes-open standing and eyes-open standing on a
sponge. [Conclusion] Using the ankle-foot orthosis was effective during the initial
training of lower limb muscle activities and the static balance training of chronic stroke
patients. However, it was not effective for a variety of dynamic situations.

BODY.INTRODUCTION:
Stroke patients are characterized by an asymmetric posture due to decreased movement, and
this asymmetric posture makes balance control in a standing posture difficult, as a result
of the center of pressure moving toward the lower limb of the unaffected side, triggering
problems with postural control ability1).
Loss of balance ability in stroke patients may cause increased postural sway, reduction of
weight on the lower limb of the affected side, and increased fall risk2).  In general, balance or postural stability refers to maintaining the center of mass within
the support surface to maintain static action and to perform desired motions. Balance
ability is essential for functional activities, as well as for actions such as sitting,
standing, and walking3). To maintain and
adjust balance, the proprioceptive, visual, and vestibular senses must interact4). However, 65% of stroke patients experience
loss of tactile and proprioceptive senses, largely because of impaired in proprioception
resulting from lowered muscle tone5).  Various methods exist to resolve problems of balance of stroke patients. These include
therapeutic exercises, such as weight shifting to the lower limb of the affected side,
proprioceptive neuromuscular facilitation techniques, Bobath techniques, neurodevelopmental
facilitation techniques, and task-oriented exercises6,
7). Repetitive exercise is necessary to
improve balance, and ankle-foot orthoses are used for hours when there is excessive
spasticity or deformity. Ankle orthoses stabilize the ankle joint and compensate for
insufficient ankle dorsiflexion and mediolateral instability of the subtalar joint,
increasing balance ability. They also facilitate medial shift of the center of mass and
weight shift toward the foot of the affected side, reducing asymmetric body posture8).  Dysfunction of the foot and the ankle joint of stroke patients are closely associated with
functional and kinetic aspects of the lumbar region and lower limbs, inevitably triggering
overall body imbalance9). The ankle joint
and the hip joint play important roles in providing body stability during stroke patients'
balance training. The first type of postural control strategy is the ankle joint strategy,
which primarily improves standing balance through muscle contraction of the ankle joint10).  While walking with an ankle-foot orthosis, the moment of the dorsiflexion angle during the
stance phase and plantarflexion during the terminal stance may increase11). In a static standing position, the ankle joint is used
frequently12), and according to
comparisons of muscular strength between those who have experienced falls and those who have
not, the extensors of the hip joint and the plantar flexor of the ankle joint show
significant differences13), indicating
that loss of balance ability is closely related to the weakening of ankle strength14). Therefore, the purpose of this study was
to examine the effects of balance training with an ankle-foot orthosis on stroke patients'
lower limb muscle activities and static balance maintenance.

BODY.SUBJECTS AND METHODS:
The subjects of this study were 25 stroke patients, and they were randomly assigned to a
group with ankle-foot orthosis shoes (AFO, n=13) and a group with shoes (n=12) (Table 1Table 1. The general characteristics of the subjectsVariablesGroupAFO Group (n=13)Shoes Group (n=12)SexMale5 (38.5%)4 (33.3%)Female8 (61.5%)8 (66.7%)DiagnosisInfarction5 (38.5%)3 (25%)Hemorrhage8 (61.5%)9 (75%)Affected sideLeft10 (76.9%)7 (58.3%)Right3 (23.1%)5 (41.7%)Onset time (months)9.0 ± 1.29.9 ± 1.0Age (years)58.9 ± 5.557.2 ± 4.4Height (cm)160.8 ± 8.5159.2 ± 7.4Weight (kg)56.6 ± 8.557.2 ± 8.2Ashworth scaleGastrocnemius2 ± 12 ± 1Values are number (%) or mean ± SD). Prior to participation in this study, the purpose was explained to the
subjects and their guardians, and they consented to participate voluntarily. The research
and development review board for human subjects of Hallym University approved this study.
All procedures conformed to the ethical principles of the Declaration of Helsinki. Inclusion
criteria were: a diagnosis of stroke within the previous 6–12 months; no evidence of
vestibular system disorders, neurological deficits in the bilateral lower limbs, or visual
or auditory disorders; a mini–mental state examination-Korean score of 23 or higher; a Berg
Balance Scale score of 40 or higher without any musculoskeletal deficit that affected
standing balance; and agreement to wear a plastic ankle-foot orthosis of the plantar flexion
90° ankle stop-type.  A Tele Myo 2400T dynamic electromyograph (EMG, Noraxon Inc. Arizona, USA) was employed to
measure muscle activities of the lower limbs. The electrodes were attached to the affected
side over the tibialis anterior muscle at one-third of the distance from the proximal
tibialis anterior muscle, and the muscle belly of the medial gastrocnemius muscle 2 cm
proximal from where the Achilles tendon encounters the medial gastrocnemius muscle. The
collected surface EMG signals were digitized using Myoresearch-XP 1.07 software: EMG signals
were sampled at 1000 Hz, bandpass-filtered between 20 to 500 Hz, and processed with a 60 Hz
notch filter.  A Tetrax Portable Multiple System (Tetrax, Tetrax Ltd, Ramat Gan, Israel) was used to
measure balance ability15). When a subject
places a foot on the force plate, the data of the pressure on the force plate is amplified
and filtered before being delivered to a computer. It is then analyzed using the Tetrax
software program. For the measurement of static balance ability, the stability index was
obtained, and the collected data were recorded as percentages of the subjects' body
weights.  The ankle-foot orthosis used in this study was a joint type, and it was appended and raised
by 1/8 of an inch so that the medial malleolus and the lateral malleolus did not meet, and
the arch support maintained or supported the longitudinal arch when it was worn. The medial
and lateral sides of the caput metatarsals tend to widen when they support weight;
therefore, each of the medial sides and the lateral sides were widened by 1/16 inch and the
orthosis was made to be a plantar flexion 90° ankle stop-type using a 5 mm thick
thermoplastic material that melted at 170 °C. The shoes were made of rubber so as not to
slide. Bands wrapped around the top of the shoes so that they were not easy to remove, and
they were made lightweight so that they could be used indoors.  Prior to and after the balance training, muscle activities and balance ability were
measured. Four balance exercises were conducted, two on flat ground and two on a balance pad
(balance pad, Airex, Switzerland) for a total of 20 minutes (Table 2Table 2. Program for balance trainingPeriodCompositionTraining methodsTimeRest0–6 weeksOn the floor Standing on two feet 1 m15 sStanding with both knees flexed1 m15 sStanding on the affected leg while holding a chair with the
unaffected arm1 m15 sAlternate leg raise: standing on a foothold 20 cm high 1 m15 s0–6 weeksOn a balance pad Standing on two feet 1 m15 sStanding with both knees flexed1 m15 sStanding on the affected leg while holding a chair with the
unaffected arm1 m15 sAlternate leg raise: standing on a foothold 20 cm high 1 m15 s)16, 17).  To measure the muscle activities in a standing position, the subject maintained a standing
position in bare feet for five seconds. Data were recorded for three seconds from the
tibialis anterior muscle and the medial gastrocnemius muscle of the affected side; the first
and the last one seconds were excluded from the data analysis. Muscle activity signals of
each muscle were converted to root mean square values, and expressed as % maximum voluntary
isometric contraction (%MVIC).  For the measurement of balance ability, the subjects stood on a hard surface with their
eyes open and with their eyes closed and on a soft pillow with their eyes open and with
their eyes closed. They maintained the standing position without holding a support.
Measurements were made three times in each position, and the average values were used the
analysis.  The statistical analysis of this study was performed using PASW 18.0. We used the
independent t-test to compare differences between the two groups, and the paired t-test to
compare within-group differences, before and after the intervention. Significance was
accepted for values of p<0.05.

BODY.RESULTS:
Muscle activity prior to and after the balance training was compared between the AFO and
shoes group. Muscle activity of the tibialis anterior muscle of the affected side of the AFO
group decreased from 19.93 ± 4.85% prior to the balance training to 16.71 ± 3.88% after the
balance training and muscle activity of the medial gastrocnemius muscle of the affected side
increased from 23.65 ± 8.10% prior to the balance training to 26.64 ± 5.83% after the
balance training, and both differences were significant (p<0.05). Muscle activity of the
tibialis anterior muscle of the affected side of the shoes group decreased from 20.26 ±
3.83% prior to the balance training to 20.23 ± 3.49% after the balance training and muscle
activity of the medial gastrocnemius muscle of the affected side increased from 24.87 ±
4.59% prior to the balance training to 25.51 ± 5.11% after the balance training; neither of
the differences was significantly different. There was a significant difference in the
muscle activities of the tibialis anterior muscle of the affected side between the AFO and
shoes groups (p<0.05) (Table 3Table 3. Comparison of muscle activities between the two groupsVariablesGroupAFO Group (n=13)Mean ± SDShoes Group (n=12) Mean ± SDPTA (%)Pre-19.93 ± 4.8520.26 ± 3.83Post-16.71 ± 3.8820.23 ± 3.49Change**−3.22 ± 0.57*−0.03 ± 0.49PMG (%)Pre-23.65 ± 8.1024.87 ± 4.59Post-26.64 ± 5.8325.51 ± 5.11Change3.00 ± 0.81*0.63 ± 0.59*indicates a significant difference between before and after, **indicates a
significant difference between the two groups, p<0.05. PTA: paralyzed side tibialis
anterior muscle, PMG: paralyzed side medial gastrocnemius, AFO: ankle foot orthosis.
Comparison within the group and comparison between the groups were made using the
paired sample t-test and the independent sample t-test, respectively.). Stability indexes prior to and after the balance training between the AFO
and shoes group were compared. For the AFO group, the stability index in a standing position
with eyes open (NO) decreased from 25.72 ± 2.98 prior to the balance training to 24.07 ±
2.90 after the balance training, the stability index in a standing position with eyes closed
(NC) decreased from 35.37 ± 7.19 prior to the balance training to 34.08 ± 6.93 after the
balance training, the stability index in a standing position on the pillow with eyes open
(PO) decreased from 30.13 ± 5.64 prior to the balance training to 29.57 ± 5.95 after the
balance training, and the stability index in a standing position on the pillow with their
eyes closed (PC) decreased from 38.80 ± 6.70 prior to the balance exercise to 35.76 ± 6.38
after the balance exercise. All differences were significant (p<0.05). For the shoes
group, the stability index showed significant decreases from 22.45 ± 4.31 to 21.05 ± 4.19 in
NO, and from 28.03 ± 6.01 to 27.01 ± 6.03 in PO (p<0.05). Regarding changes in stability
index resulting from balance training, there was a significant difference in NO between the
AFO group and the shoes group (p<0.05) (Table
4Table 4. Comparison of the stability index between the two groupsCondition GroupAFO Group (n=13)Mean ± SDShoes Group (n=12)Mean ± SDNOPre-25.72 ± 2.9822.45 ± 4.31Post-24.07 ± 2.9021.05 ± 4.19Change**−1.65 ± 0.74*−1.40 ± 0.80*NCPre-35.37 ± 7.1931.57 ± 9.28Post-34.08 ± 6.9330.52 ± 10.04Change−1.29 ± 1.35*−1.05 ± 3.22POPre-30.13 ± 5.6428.03 ± 6.01Post-29.57 ± 5.9527.01 ± 6.03Change−0.56 ± 0.59*−1.02 ± 1.20*PCPre-38.80 ± 6.7032.37 ± 7.51Post-35.76 ± 6.3832.25 ± 7.26Change−3.05 ± 1.75*−0.13 ± 1.40*indicates a significant difference between before and after, **indicates a
significant difference between the two groups, p<0.05. NO: normal open, NC: normal
close, PO: pillow open, PC: pillow close, AFO: ankle foot orthosis. Comparison within
the group and comparison between the groups were made using the paired sample t-test
and the independent sample t-test, respectively.).

BODY.DISCUSSION:
This study examined the effects of ankle-foot orthosis during balance training of chronic
stroke patients on muscle activities and static balance of the lower limbs of stroke
patients. After the six weeks of balance training, the data of the two groups were compared
to examine muscle activities and static balance around the ankles related to wearing of the
ankle-foot orthosis. The stability index was significantly different in the NO condition
between the groups, and the AFO group showed statistically significant differences in all
conditions between prior to and after the balance training. The changes in AFO group muscle
activities were significantly greater than those of the shoes group.  After balance training with the ankle-foot orthosis, there was no significant difference in
the medial gastrocnemius muscle activity of the affected side, but there was a significant
difference in the tibialis anterior muscle activity of the affected side. During balance
training with the ankle-foot orthosis, the muscle activity of the tibialis anterior muscle
of the affected side decreased and the muscle activity of the medial gastrocnemius muscle
increased. However, in the group without the ankle-foot orthosis, there was no pre-post
statistically significant difference in either the muscle activity of the tibialis anterior
muscle or the medial gastrocnemius muscle of the affected side. This result is consistent
with a study in which the ankle muscle activities of nine males and one female in a static
standing posture were examined, and the use of the ankle plantar flexor was predominant18). It is also in agreement with a study in
which the anterior-posterior center of pressure of six multiple sclerosis patients and four
ordinary subjects were examined in a standing position and the use of the gastrocnemius was
predominant19). However, an ankle-foot
orthosis used postural adjustment by 42 stroke patients whose onset of a stroke was 6 months
prior or earlier, and 61 stroke patients whose onset of a stroke was 12 months ago or
longer, was effective at providing stability for the ankle of early phase stroke patients
but not chronic phase stroke patients, as structural changes has occurred, including changes
in alignment and muscle shortening20).  There was a statistically significant difference in the stability index of NO between the
AFO and shoes group, but there were no statistically significant differences in NC, PO, and
PC between the two groups. In the group who wore the ankle-foot orthosis, there were
significant differences in the stability indexes of NO, NC, PO, and PC, and in the group who
wore only shoes, there were significant differences in NO and PO. This result is similar to
that of study in which postural sway of 28 stroke and traumatic brain injury patients was
measured with and without an ankle-foot orthosis; when the ankle-foot orthosis was worn,
postural sway was small2). Our results are
also consistent with those of a study in which balance maintenance of 11 stroke patients and
10 ordinary subjects wearing an ankle-foot orthosis was examined: weight shift to the
lateral side and an increase in weight bearing on the affected side resulted in more use of
an ankle strategy than a hip strategy for stability4). In the rehabilitation process of stroke patients, improvement of
balance ability is important. In prescribing orthoses, improvement in balance ability and
gait should be considered. In general, use of an ankle-foot orthosis may be helpful for some
stroke patients' balance, but stroke patients differ in degree and area of anatomical
damage. Therefore, changes must be made in accordance with their environment and condition.
Balance training variables appropriate for patients should be selected, and effective
treatment methods should be utilized to maximize patients' potential capabilities.
Generalization of this study is limited, as only those patients meeting the selection
criteria were examined. Future research that includes the same kind of patients with
classification of etiology and brain lesions is necessary.

Question: Compared to patients wore only their shoes what was the result of ankle-foot orthosis (AFO) group on Muscle activity of the tibialis anterior muscle - inpatients receiving physical therapy for chronic stroke?
Evidence: Using the ankle-foot orthosis was effective during the initial
training of lower limb muscle activities 
Answer: significantly decreased