# Neuromechanical Modeling of Postural Responses:Mechanisms of Balance Impairments in Parkinson's Disease

> **NIH NIH R01** · EMORY UNIVERSITY · 2021 · $491,750

## Abstract

Our long-term goal is to advance our scientific knowledge and computational approaches to identify causes of
balance impairments leading to falls in Parkinson’s disease (PD) to guide the rational development more
effective treatments and rehabilitation for improving balance. Recent insights from our neuromechanical
simulation studies in tandem with our ongoing work characterizing changes reactive balance control after
rehabilitation in people with PD have implicated our overall hypothesis that the cardinal parkinsonian sign of
rigidity is a cause of balance impairments. Rigidity is not typically considered in fall risk, yet our ongoing
studies demonstrate a previously-unreported association between leg rigidity and prior falls. We believe that
identifying the causes of this association will lead to improved diagnosis and treatment of balance impairments
in PD. Our objective is to identify the effects of leg rigidity on postural robustness, defined as the ability to
maintain the feet in place in reactive balance. Based on our neuromechanical simulations, we hypothesize
that parkinsonian rigidity increases two distinct aspects of postural muscle activity that can each reduce
postural robustness: tonic muscle activity, defined as the magnitude of muscle activity in static postures, and
dynamic muscle activity is defined as the magnitude and timing of muscle activity generated by sensorimotor
feedback in reactive balance. We will use combined experimental and computational approaches to
systematically isolate the causal linkages and interactions between rigidity, muscle activity, and postural
robustness in PD. In addition to electromyographic (EMG) recordings, we will also establish the reliability of
measuring tonic muscle activity during standing using frequency domain near-infrared spectroscopy (FDNIRS)
combined with diffuse correlation spectroscopy (DCS). In Aim 1 we will test well-characterized PD participants
with confirmed dopamine-responsive rigidity to identify the effects of leg rigidity on tonic muscle activity,
dynamic muscle activity, and postural robustness; we will manipulate rigidity using dopamine medication and
an activation maneuver. In Aim 2 we will test neurotypical participants to identify causal role of modulating
tonic and dynamic muscle activity on postural robustness; we will modulate muscle activity using EMG
biofeedback and adaptation. In Aim 3 we will develop neuromechanical simulations to quantitatively
demonstrate mechanistic relationships between tonic muscle activity, dynamic muscle activity, and postural
robustness. We will augment our neuromechanical models of balance with agonist-antagonist muscle models.
If successful, we will 1) identify the causal role of rigidity on impaired balance in PD, 2) validate a novel
and clinically-feasible method (NIRS) to measure rigidity in functionally-relevant tasks, and 3) establish a
broadly extendable generative neuromechanical model of balance to simulate how multiple mechanis...

## Key facts

- **NIH application ID:** 10174970
- **Project number:** 5R01HD046922-15
- **Recipient organization:** EMORY UNIVERSITY
- **Principal Investigator:** Lena H Ting
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $491,750
- **Award type:** 5
- **Project period:** 2004-04-01 → 2023-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10174970

## Citation

> US National Institutes of Health, RePORTER application 10174970, Neuromechanical Modeling of Postural Responses:Mechanisms of Balance Impairments in Parkinson's Disease (5R01HD046922-15). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10174970. Licensed CC0.

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