# Elastic mechanisms in locomotion

> **NIH NIH R01** · BROWN UNIVERSITY · 2020 · $422,310

## Abstract

Project Summary
The biological springs that act in parallel and in series with skeletal muscle can significantly
influence the force, power and displacement of muscle fibers during locomotion. All movements
involve dynamic interactions between passive elastic structures and muscle contractile
elements, but our understanding of the consequences of this interaction for both normal and
pathological gait is limited. Our long-term goal is to define the mechanical influence of elastic
elements on muscle force production and gait. This project aims to understand how the
mechanical interaction between internal muscle elastic elements and forces produced by
muscle fibers define the gear ratio with which muscles operate. Previous work shows that this
interaction significantly influences muscle force and speed, and we hypothesize that the
influence of internal elastic elements on muscle shape changes underlies deficits in muscle
performance in aging and many neuromuscular disorders. The project aims to construct and
test a model of muscle shape change that can predict the influence of muscle force and muscle
elastic properties on the gear ratio with which pennate muscles produce force. This project
combines unique animal model systems with novel measurement techniques to make direct
measurements of muscle force, muscle shape, and fiber length change both in vivo and in
isolated muscles. The specific aims of the project are: 1) to develop a predictive model of
muscle shape change and gearing 2) to use a series of studies of muscle function in vivo and in
situ to test and refine this model; 3) to test the hypothesis that external constraints can influence
muscle force output via their effect on muscle bulging, and 4) to test the hypothesis that
restrictions to muscle bulging due to stiffened extracellular matrix reduce muscle force output in
aged muscles.
Changes in the elastic properties of connective tissue elements within muscle are associated
with several neuromuscular disorders, aging, and occur secondarily to stroke and spinal cord
injury. A fundamental understanding of the influence of these elements on muscle mechanical
function will inform the design of rehabilitative strategies and interventions to improve muscle-
tendon function. An improved understanding of how muscle elastic elements influence the
mechanical behavior of healthy muscle-tendon units may also aid in the design of prosthetic
devices.

## Key facts

- **NIH application ID:** 9926817
- **Project number:** 5R01AR055295-12
- **Recipient organization:** BROWN UNIVERSITY
- **Principal Investigator:** EMANUEL AZIZI
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $422,310
- **Award type:** 5
- **Project period:** 2008-08-01 → 2023-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9926817

## Citation

> US National Institutes of Health, RePORTER application 9926817, Elastic mechanisms in locomotion (5R01AR055295-12). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/9926817. Licensed CC0.

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