Characteristics of Balance Control to Unexpected Loss of Balance During Standing and Walking in Post-stroke Individuals
Phase: EARLY_PHASE1
Conditions: Stroke
Sponsor: Nachum Soroker, MD

 
 
Characteristics of Balance Control to Unexpected Loss of 
Balance During Standing and Walking in Post-stroke Individuals 
 
 
#NCT02619175 
 
 
Date: 09.02.2019 
 
 
 
 
 
 
 
 
 
 
 

Protocol 
Participants 
PwS were recruited during their hospitalization at the Loewenstein Rehabilitation 
Hospital (LRH), Ra’anana, Israel between November 2016 to February 2018. 
Inclusion criteria included first unilateral stroke, being able to walk with or without 
a walking aid independently or under supervision. Exclusion criteria included 
body weight greater than 135 kg, other neurological disorders, severe arthritis, 
joint replacement surgery and blindness, confirmed by the individuals’ physician 
and medical record at the time of enrollment. The study was approved by the 
Institutional Review Board at the Loewenstein Hospital (approval number LOE-
14-0021). Participants signed a written informed consent according to the 
declaration of Helsinki. 
Study design 
Subacute PwS were randomized to perturbation-based balance training 
(PBBT) or weight shifting and gait training (WS&GT). Allocation was made by 
an investigator not involved in the assessments using computer random 
allocation software (Random Allocation Software Version 1.1, Isfahan Iran). 
Participants were tested before and after the training period by a blinded 
investigator. PwS in the PBBT and WS&GT groups received 12 training 
sessions, each session lasted 30 minutes, 1 training session per day over a 
period of 2.5 weeks. Pretraining (T1) and post training (T2) assessments 
included laboratory reactive balance capacity functions and clinical measures 
of balance, gait, motor impairments, and balance confidence. Follow-up 
assessment (T3) conducted 5 weeks after intervention completion and included 
only assessment of reactive balance capacity. All assessment sessions were 
performed at the same time of day and in the same order. 
Assessment Protocol  
Participants stood on a computerized mechatronic treadmill system that provides 
unannounced perturbations by a horizontal movable platform (Balance Tutor, 
MediTouch Ltd, Israel), wearing a safety harness that prevented falls but did not 

restrict their movements. Surface translations were increased systematically in 6 
intensities from low (intensity 1) to high (intensity 6) for a total of 24 perturbation 
trials (characteristics of perturbation intensities are described in Table 1).. 
Participants were instructed to stand with feet placed together and to react 
naturally to prevent themselves from falling. A safety harness system was 
attached to an overhead track via rope. Rope length was adjusted individually so 
it would prevent participants’ knees from touching the treadmill belt in case of fall. 
In case of a fall into harness, the participant did not continue to higher intensity. 
Participants performed all trials wearing their own sport shoes and foot orthosis 
in case they needed ankle support. 
Outcome measures 
Reactive balance capacity was assessed by multiple-step threshold and fall 
threshold. Multiple-step threshold was defined as the minimum perturbation intensity 
that consistently elicits 2 or more compensatory steps that extended the base of 
support in at least 2 consecutive perturbation intensities. Fall threshold was defined 
as the perturbation intensity that results in unsuccessful balance recovery, that is, 
when a subject was unambiguously supported by the harness system. Multiple-step 
threshold and fall threshold have been found to demonstrate high interrater and test 
retest reliability in healthy adults. In case a participant did not fall at the highest 
perturbation intensity (intensity 6), his or her fall threshold was calculated as 
intensity 7. Reactive step initiation time, step length and step velocity were 
measured using a three-dimensional motion analysis system (APAS inc).  
A day prior to the reactive balance assessment, PwS underwent a clinical 
assessment that included the lower extremity Fugl-Meyer (LEFM) assessment, 
Berg Balance Scale (BBS), 10-meter walk test (10MWT), 6-minute walk test 
(6MWT), and Activity-specific Balance Confidence (ABC) scale. These 
measures have been found to demonstrate strong interrater and test-retest 
reliability in PwS. 
 
 
 

Intervention Programs 
Group 1 - Perturbations based balance training 
In the PBBT group, each training session consisted of 36 random 
right/left/forward/backward unannounced platform translations while standing 
(i.e, 3 blocks of 12 perturbations) and 30 random right/left perturbations during a 
10- to 12-minute treadmill walk (Balance Tutor, MediTouch Ltd, Israel). 
Perturbations were synchronized to the single support phase of gait cycle using 
the Balance Tutors’ inertial sensors. Perturbations were unpredicted in terms of 
time and direction. The instruction was “try to prevent yourself from falling.” In the 
first training session, the initial perturbation intensity was individually adjusted 
according to participant’s maximal ability, that is, the maximal perturbation 
intensity that could be recovered without falling into harness system during the 
baseline assessment. Progression to higher intensity occurred if the participant 
was able to recover from 24 consecutive perturbations (2 blocks of 12 
perturbations) without a fall and felt that he or she could be further challenged. 
The increase in intensity during training was constant and a function of the 
following perturbation parameters: in forward and backward perturbations: 
distance = 1.86 cm, velocity = 3.65 cm/s, and acceleration = 11.72 cm/s2 and in 
response to lateral perturbations: distance = 1.17 cm, velocity = 3.79 cm/s, and 
acceleration = 12.07 cm/s2. 
Group 2 – Weight shifting and gait training (control) 
In the WS&GT group, each session consisted of 36 voluntary weight shifting 
exercises (3 blocks of 12 targets) delivered in a random order while standing on 
a computerized force platform (Balance Master, NeuroCom International Inc) and 
a 10- to 12-minute treadmill walk without perturbations. For weight shifting, 
participants stood on a force platform while viewing a display of their center of 
pressure position relative to a target on a screen. They were instructed to shift 
weight in order to reach the target without changing their feet position or falling. 
In the first session, the initial distance for weight shifting was individually adjusted 
for each participant as the maximal distance he or she could shift weight without 
falling into harness or changing their feet position. The distance to target was 
increased by 5% if the participant was able to complete a set of 24 consecutive 

weight siftings without falling or changing their feet position and felt that he or she 
could be further challenged (Figure 2). Participants in both groups walked at their 
preferred treadmill walking speed that was adjusted during sessions according to 
their abilities. In case the participants needed, support was given by the 
therapist’s hand. To increase task difﬁculty in both groups a concurrent cognitive 
task was added (backward counting by 3 or 7) in training sessions 9 to 12. 
Participants were provided information regarding knowledge of the results of the 
balance reaction, that is, the occurrence of a fall into harness, through information 
inherent in the task (the pull of the harness) and verbal feedback regarding 
perturbation intensity/weight shifting distance and walking speed. At the end of 
each session participants were asked to rate their perceived level of challenge 
on a 0-to-10 scale where 0 represents no challenge and 10 represents very high 
challenge. During the study period, PwS continued with their regular rehabilitation 
therapies that included daily physical therapy and occupational therapy 
treatments and if needed, speech therapy treatment. All measurement and 
training sessions were conducted by physical therapists working in neurological 
rehabilitation. 
Statistical analyses 
Baseline characteristics will be compared using independent-samples t test for 
continuous variables, Mann-Whitney U test for ordinal variables or variables with 
non-normal distributions, and chi-square test for categorical data. A mixed 
factorial analysis of variance for normally distributed dependent variables will be 
conducted. The independent variables are group (PBBT, WS&GT) and time 
(baselineT1, postintervention-T2, follow-up-T3). In case of non-normal 
distributions or ordinal variables the Mann-Whitney U test will be used to compare 
group-by-time interactions by computing the differences between post 
intervention and baseline performances (T2−T1) and between follow-up and 
baseline performances (T3−T1).  
 
 
 
 
 
 

 
 
 
Table 1. Perturbation parameters by perturbation intensity and direction.   
Perturbation 
Intensity 
Forward/Backward surface 
translation 
Rightward/Leftward surface 
translation 
Distance 
(cm) 
Velocity 
(cm/sec) 
Acceleration 
(cm/sec2) 
Distance 
(cm) 
Velocity 
(cm/sec) 
Acceleration 
(cm/sec2) 
1 
10.44 
17.62 
126.89 
5.68 
20.17 
73.27 
2 
14.17 
24.93 
150.34 
8.03 
27.75 
97.41 
3 
17.89 
32.24 
173.79 
10.37 
35.34 
121.55 
4 
21.62 
39.55 
197.24 
12.72 
42.93 
145.68 
5 
25.34 
46.86 
220.69 
15.06 
50.51 
169.82 
6 
29.06 
54.17 
244.13 
17.41 
58.10 
193.96 
Abbreviation: cm, centimetre; cm/sec, centimetre per second; cm/sec2, centimetre per 
second square. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 
 
 

 
 

 
 

 
 

 
 
 
 
 
 

ACTIVITIES-SPECIFIC BALANCE CONFIDENCE (ABC) SCALE 
 
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Powell LE & Myers AM. The Activities-specific Balance Confidence (ABC) Scale. J Gerontol Med Sci 1995; 
50 (1):M28-34 
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