1.0 Background/Scientific Rationale Interventions such as conventional balance and
exercise training constitute a major part of stroke rehabilitation and improve volitional
balance control and gait in people with chronic hemiparetic stroke (PwCHS). However, they
seldom target reactive balance (compensatory postural responses such as stepping) that
forms the first line of defense while recovering from a balance loss. Reactive balance in
PwCHS is affected by deficits in perturbation-evoked neuromuscular and biomechanical
responses especially during gait. Further, previous research has shown that stability and
adaptions to repeated perturbations is more affected on paretic compared to non-paretic
limb. Thus, paretic limb deficits are postulated to be key contributors of falls in
ambulatory PwCHS. Perturbation-based reactive balance training (REACT) is widely
recognized as an intervention that reduces falls by improving fall-resisting skills. In
the past five years, there is a 3-fold increase in perturbation training research in
PwCHS (mostly low impairment). Thus, limited evidence exists for PwCHS with severe motor
impairment who might not show similar tolerance or learning abilities.
Complementing REACT with interventions known to facilitate paretic limb performance and
motor learning (i.e., neuromuscular electrical stimulation, NMES) can improve therapeutic
effects of REACT and hence its clinical translation for PwCHS and other populations that
could benefit from fall-risk reduction. While it is established that REACT programs and
NMES can induce motor learning in behavioral variables, there is limited evidence on
neuroplastic changes and exact neural mechanisms underlying these behavioral changes
(especially during REACT). Similar to the precision medicine approach, modifiable
causative factors, contributors, and mediators to falls must be targeted when designing
effective falls prevention interventions that reduce training times and/or facilitate the
inclusion of persons with high impairment.
This project aims to describe whether a specific pattern of lower limb muscle stimulation
could modify the recovery response after an unexpected perturbation in the form of a slip
and/or trip in individuals with stroke. Also, this study aims to examine the
effectiveness of 6-weeks of reactive balance training (REACT) with and without
neuromuscular electrical stimulation (NMES) to paretic lower limb muscles on
biomechanical, clinical, neuromuscular and neuroplastic outcomes of reactive balance
control.
2.0 Objectives/Aims
The specific aims of this study are below:
Aim 1: To examine effects of synchronous REACT+NMES on reactive balance control and
clinical outcomes among people with chronic stroke with moderate to severe motor
impairment.
H1.1: REACT+NMES will induce greater improvement in biomechanical outcomes of reactive
balance (reactive stability, limb support) resulting in fewer laboratory falls
post-training than REACT+ShamNMES (at 6 weeks).
H1.2: The improvements in reactive balance control in REACT+NMES will translate to
greater improvement in clinical outcomes of balance (mini-BEST test), gait (10m walk
test) and falls-efficacy (Activities specific Balance Confidence scores) than REACT.
H1.3: The improvements in reactive balance control will also translate to reduced falls
during overground gait-slips after REACT+NMES.
Aim 2: To examine neuromuscular and neuroplastic effects of REACT+NMES in PwCHS with
moderate to severe motor impairment.
H2.1. REACT+NMES will induce greater neuromuscular (muscle synergy #s and activations)
and neuroplastic (perturbation evoked potentials- PEPs) changes post-training than REACT
(at 6 weeks).
H2.2: Baseline PEP amplitude and training-induced neuroplastic changes in PEP's will
correlate with the training-induced improvements in biomechanical and neuromuscular
responses.
3.0 Research Design This study trial employs a two-arm, double-blinded, randomized
controlled trial (RCT) design This study will examine efficacy and feasibility of
REACT-NMES intervention compared to REACT+ShamNMES among PwCHS with moderate to severe
motor impairment (Aim 1 and 2) A sample size of 46 chronic stroke survivors will be
enrolled, undergo initial screening and pre-training assessment, and then randomized into
two groups (intervention and control). Next, both groups will undergo 6-weeks of in-lab
reactive balance training (2x/week, total 12 sessions). After training, participants in
both groups will undergo a post-training assessment, which will include all the tests
performed in the pre-training assessment.
Study overview: All participants will undergo the following procedures.
Session 1 (Week 1): Initial screening (2 hours)
Session 2 (Week 2): Pre-test (total 4 hours)
Session 3-15 (Week 3-8): Training sessions (2 hours/session, 2 times/week for 6
weeks) (total: 24 hours)
Session 16 (Week 9): Post-test (total 4 hours)
