The Motor Control Consequences of Excessive Physical Therapist Support in Individuals With Stroke
Phase: NA
Conditions: Stroke
Sponsor: University of Cincinnati

 
  
 
 
 
 
 
 
 
 
 
 
 
The Motor Control Consequences of Excessive Physical Therapist Support in 
Individuals with Stroke (NCT04856527) 
 
University of Cincinnati IRB Protocol 2020-1072 
 
Most recent IRB approval: 2021-10-07 
 
 
 
 
 
 
STUDY PROTOCOL AND STATISTICAL ANALYSIS PLAN 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 
MOTOR CONTROL PHYSICAL THERAPIST SUPPORT STROKE 
1 
 
 
Study Protocol 
 
Participants 
Twenty participants aged 21-85 years1 previously diagnosed with stroke (>1-month prior 
to enrollment to ensure medical neurologic stability) will participate in Experiment 1 (10 
participants in experimental group, 10 participants in control group). Participants will be 
randomly assigned to a group. Participants must demonstrate independence or modified 
independence during ambulation (defined as the ability to ambulate with no physical 
assistance and use an assistive device as needed). Participants must score 0-3 on the 
Modified Rankin Scale (de Haan et al., 1995; Rankin, 1957), which indicates complete 
independence to moderate disability but able to walk without assistance. Participants 
must be able to maintain standing balance for >2 minutes with no physical support and 
maintain grasp of a handheld object with at least one hand. Participants are permitted to 
be active in programs of physical therapy or occupational therapy at the time of 
enrollment. All gender identities and all races/ethnicities will be eligible for participation.  
 
Participants with stroke will be excluded due to limited language/cognitive abilities, 
deafness, blindness, or serious motor impairment that outright prevents performance of 
the experimental tasks (e.g., severe upper or lower extremity spasticity). Participants will 
be excluded if they are pregnant. Participants will also be excluded if they experience 
pain with weightbearing >4/10. Participants will complete the Mini Mental State Exam 
(Folstein et al., 1975) prior to study start to ensure cognitive capacity to engage in and 
consent to the study. Participants will be excluded if they have any other medical condition 
that would preclude the valid administration of the study measures, specifically seizure 
disorders, additional neurologic conditions beyond stroke, or significant musculoskeletal 
conditions (e.g., lower limb amputation). 
 
Participants with stroke will be recruited from a large outpatient neurologic rehabilitation 
clinic part of a larger, nonprofit medical center in the midwestern United States. Further, 
participants will also be recruited from the UC Stroke Recovery Registry. This registry 
contains over 750 persons with chronic stroke who have expressed a desire to be 
involved in stroke-related research at UC. The registry is shared among researchers in 
the College of Allied Health Sciences, the College of Medicine, and the College of 
Nursing. All participants will receive compensation for time and travel.  
 
Materials and Apparatus 
 
Participants will be placed in a virtual environment created with the Unity game engine 
(Unity Technologies, San Francisco, CA) while donning a VIVE virtual reality (VR) 
headset (HTC Corporation, Bellevue, WA). Postural sway will be measured using a force 
platform (AMTI AccuSway, Advanced Mechanical Technology, Watertown, MA). For the 
 
1 This is the age range approved by the IRB. Age range will be narrowed once it is ascertained what range 
is available for recruitment. Most likely, participants will be > 60 years. However, if a large sample of younger 
adults < 45 years is available, that will become an eligibility criterion, and the study will be conducted with 
young adults with stroke. 

 
MOTOR CONTROL PHYSICAL THERAPIST SUPPORT STROKE 
2 
 
transfer task, light finger force production will be measured with a 1500 g force transducer 
(Measurement Specialties, Inc., Dayton, OH). A visual display created in Processing 
(v.3.5.4) will communicate level of light force production to participants. The virtual 
environment will be rendered at a rate of 90 Hz. Postural sway data and light force 
production will be sampled continuously at a rate of 150 Hz.  
 
Experiment 1: Postural Support and Task Learning 
 
Pre-Test 
In Experiment 1, participants will be required to learn an upper limb precision aiming task 
while receiving postural support (i.e., balance facilitation) or no postural support. Baseline 
performance will be measured prior to a practice period. For this pre-test, participants will 
stand on the force platform for 30 s trials. Within the VR environment, participants will see 
an anteriorly placed circular target and will be instructed to maintain the position of a 
virtual laser pointer in the target via a handheld device in the dominant hand (or both the 
non-paretic and paretic hands for participants with stroke) with the upper limb held at the 
side. The target will change color to communicate task accuracy to participants: When 
the virtual laser is correctly positioned within the target, the target will be blue, but 
misaiming will turn the target red, indicating the need to correct the laser position. 
Participants will only visualize the laser and target in VR; there will not be a virtual 
representation of the upper limb. Participants with stroke will complete two 30 s pre-test 
trials with each hand (paretic and non-paretic). Postural sway and projection of the laser 
will be measured and recorded.  
 
Transfer Task 
As therapists expect that training in a set of tasks might benefit performance of other 
similar but untrained tasks (i.e., transfer), a task to assess transfer will also be 
implemented. This task will be completed both prior to the practice period (to obtain a 
baseline level of performance for comparison after practice) and after the practice period. 
In the transfer task, participants will attempt to use their dominant hand (or both non-
paretic hand and paretic hand for participants with stroke) second digit to produce a 
specified level of light touch force (0.5-1 N to prevent physical stabilization) on the force 
transducer. Like the laser pointer task, this task requires integration of postural control 
with precision manual performance (e.g., Riley et al., 1999b). Participants will receive 
visual feedback regarding their level of light touch force production on a visual display. A 
vertical bar will appear on the screen. The bar will increase in vertical size with increased 
force production and decrease in size with less force production. The bar will change color 
to reflect the level of force production. When the bar is blue, the desired level of force 
production has been achieved. When the bar is red, the participant needs to alter the level 
of force production. A horizontal line will also indicate target force production. Participants 
will complete two 30 s trials of the transfer task. Participants with stroke will complete the 
transfer trials with each limb. 
 
Practice 
Following the pre-test and baseline transfer task, participants will engage in 10, 1 min 
practice blocks in which they are to practice the laser task with the target positioned 

 
MOTOR CONTROL PHYSICAL THERAPIST SUPPORT STROKE 
3 
 
laterally. This lateral placement of the target during the practice period (as opposed to the 
anterior position of the pre-test) will prevent one group of participants from practicing 
under the exact conditions of the pre-test, which could bias the results. This will also allow 
for an assessment of differences in sway variability that may facilitate performance at 
post-test, thus providing insights about generalizability. The control group will receive no 
physical support to maintain balance. The experimental group will receive physical 
support (whether physical support is warranted or not) to minimize postural sway 
fluctuations. Participants with stroke will use the paretic hand. Participants will be outfitted 
with a gait belt, and physical support will be provided through the use of the gait belt and 
other traditional physical therapy guarding techniques (O’Sullivan et al., 2019). Thus, 
participants in this group will not be required to coordinate posture and task performance 
because postural stabilization will be provided externally through physical support. 
Postural sway and virtual laser position will be synchronously recorded during the practice 
period. Participants will rest for a self-selected period between each trial. 
 
Immediate Post-Test and Retention 
Participants will complete a post-test following the same procedure as the pre-test (i.e., 
target task). The post-test will also involve the previously described transfer task. 
Participants will complete two 30 s trials of each task (target/force production). 
Participants with stroke will complete the trials with each limb. Task and condition will be 
randomized. No physical support will be provided in the post-test.  
 
Design 
 
To evaluate the learning effect in participants with stroke, the two groups (experimental, 
control), two hands (paretic, non-paretic), and two test conditions (pre-test, immediate 
post-test) will result in a 2 × 2 × 2 mixed design for Experiment 1. Participants with stroke 
will complete 2 trials of each test condition per limb for a total of 8 test trials per participant. 
To evaluate the role of therapist support during practice, each participant will complete 
10 practice trials. Participants will complete 4 trials (2 trials per limb) of the transfer task 
before and after practice for a total of 8 trials.  
 
Proposed Data Analysis 
 
All data processing and analyses will be completed using custom R scripts (v.4.0.3). All 
postural sway data (i.e., center of pressure—COP) will be filtered through a 4th-order 
lowpass zero-lag Butterworth filter with a cut-off frequency of 6 Hz prior to analysis. 
 
Recurrence Quantification Analysis (RQA) 
RQA (Webber & Zbilut, 2005) will be used to assess the regularity of postural sway. RQA 
quantifies the patterning, non-stationarity, and complexity of biological time series through 
the analysis of local recurrences in a reconstructed phase space (Riley et al., 1999a). 
Recurrence plots (RPs) provide a visualization of patterns of recurrence, where a single 
point on the RP indicates a recurrence and a line indicates continuing recurrence (Coco 
& Dale, 2014). A variety of metrics are used to quantify these patterns. Percent 
determinism (%DET) is the percentage of recurrent points which fall on diagonal lines 

 
MOTOR CONTROL PHYSICAL THERAPIST SUPPORT STROKE 
4 
 
and reflects how often the system repeats the same sequence of points. Thus, higher 
%DET is indicative of a system with more regularity. Maximum line length (MAXLINE) is 
the length of the longest diagonal line segment on the RP, indicating the maximum 
duration of time that the system is revisiting an area of reconstructed phase space. Mean 
line length (MEANLINE) is the average length of diagonal line segments on the RP, 
indicating the average duration of time that the system is revisiting an area of phase 
space. In the context of the current study, reduced task-sensitive adjustments (i.e., 
modulation in task relevant direction) in %DET, MAXLINE, and MEANLINE of postural 
sway (hypothesized to exist following constraining posture/task) would indicate a more 
regular postural control system—one that is prone to repeating the same behaviors. RQA 
metrics will be calculated separately for each plane. 
 
Sample Entropy (SampEn) 
SampEn (Richman, Lake, & Moorman, 2004) will be used to evaluate changes in the 
predictability of postural sway as a convergent measure to complement RQA. SampEn 
evaluates the predictability of the next state of a system, given what is known about the 
current state of a system (Yentes, 2016). SampEn has been widely used to assess the 
regularity of postural control across a variety of task conditions and populations (e.g., 
Schmit et al., 2016). SampEn will be calculated separately for each plane. 
 
Traditional Analyses 
Due to the wide use of COP path length and standard deviation (SD) of COP in the 
literature, these metrics will also be measured to further quantify changes in postural 
sway. These metrics are also important for assessing the distribution of sway in each 
plane as a function of task demand. COP path length refers to the amount of displacement 
of the location of the (resultant) vertical ground reaction force vector.  Increased COP 
path length is often interpreted as reduced stability. SD of the COP is the typical method 
used to quantify the variability in COP trajectories. Higher values for SD of the COP 
indicate increased variability. COP path length is a bi-planar measure whereas SD of the 
COP will be calculated separately for each plane. 
 
Supra-Postural Task Performance 
Root mean square (RMS) deviation of the observed supra-postural task performance 
from the expected values will be used to determine the accuracy of supra-postural task 
performance. For Experiments 1 and 2, this will be defined as the deviation of the laser 
position from the target. For the transfer task, this will be defined as the deviation from 
the target range of light touch force production.  
 
Statistical Analysis 
To characterize learning of the practiced supra-postural laser/target task and the 
associated postural sway patterns, trials (error score and postural sway metrics) for both 
experiments will be submitted to mixed-effects models. Group (experimental, control), 
test condition (pre-test, immediate post-test), limb (paretic, non-paretic), and their 
interactions will be entered as fixed effects, and participant will be entered as a random 
effect. To assess performance (error score and postural sway metrics) during the practice 
period, trial number (1-10), group (experimental, control), and their interaction will be 

 
MOTOR CONTROL PHYSICAL THERAPIST SUPPORT STROKE 
5 
 
entered as fixed effects and participant will be a random effect. For the transfer task (error 
score and postural sway metrics), group (experimental, control), test condition (pre-test, 
immediate post-test), limb (paretic, non-paretic), and their interactions will be entered as 
fixed effects, and participant will be entered as a random effect. A backward stepwise 
approach will be used for model building. Simple effects and pairwise comparisons will 
be used to follow up on significant interactions.  
 
Relevant References 
Balasubramaniam, R., Riley, M. A., & Turvey, M. T. (2000). Specificity of postural sway 
to the demands of a precision task. Gait & Posture, 11(1), 12-24. 
Coco, M. I., & Dale, R. (2014). Cross-recurrence quantification analysis of categorical and 
continuous time series: An R package. Frontiers in Psychology, 5, 510, 1-14. 
de Haan, R., Limburg, M., Bossuyt, P., Van der Meulen, J., & Aaronson, N. (1995). The 
clinical meaning of Rankin ‘handicap’ grades after stroke. Stroke, 26(11), 2027-
2030. 
Folstein, M. F., Folstein, S. E., & McHugh, P. R. (1975). “Mini-mental state”: a practical 
method for grading the cognitive state of patients for the clinician. Journal of 
Psychiatric Research, 12(3), 189-198. 
McCamley, J. & Harrison, S. J. (2016). Introduction. In N. Stergiou (Ed.), Nonlinear 
analysis for human variability (pp. 1-28). Boca Raton, FL: CRC Press. 
O’Sullivan, S. B., & Schmitz T. J. (2007). Physical rehabilitation (5th ed.). Philadelphia, 
PA: FA Davis. 
O'Sullivan, S. B., Schmitz, T. J., & Fulk, G. (2019). Physical rehabilitation (6th ed.). 
Philadelphia, PA: FA Davis. 
Rankin, J. (1957). Cerebral vascular accidents in patients over the age of 60: II. 
Prognosis. Scottish Medical Journal, 2(5), 200-215. 
Richman, J. S., Lake, D. E., & Moorman, J. R. (2004). Sample entropy. In Methods in 
Enzymology 
(Vol. 
384, 
pp. 
172-184). 
https://doi.org/10.1016/S0076-
6879(04)84011-4. 
Riley, M.A., Balasubramaniam, R., & Turvey, M.T. (1999a). Recurrence quantification 
analysis of postural fluctuations. Gait & Posture, 9(1), 65-78 
Riley, M. A., Stoffregen, T. A., Grocki, M. J., & Turvey, M. T. (1999b). Postural stabilization 
for the control of touching. Human Movement Science, 18(6), 795-817. 
Webber, C. L., & Zbilut, J. P. (2005). Recurrence quantification analysis of nonlinear 
dynamical systems. In M. A. Riley & G. C. Van Orden (Eds.), Tutorials in 
contemporary nonlinear methods for the behavioral sciences (pp. 26-94). 
Retrieved from https://www.nsf.gov/ pubs/2005/nsf05057/nmbs/nmbs.pdf. 
World Health Organization. (2001). International classification of functioning, disability 
and health: ICF. Geneva: World Health Organization. 
Yentes, J. M. (2016). Entropy. In N. Stergiou (Ed.), Nonlinear analysis for human 
variability (pp. 173-260). Boca Raton, FL: CRC Press.