# Development and Validation of a Rodent FES Bicycle System

> **NIH VA I21** · VETERANS HEALTH ADMINISTRATION · 2024 · —

## Abstract

Bone loss is a hallmark of severe spinal cord injury (SCI) that increases risk of fracture and contributes to the
development of medical comorbidities that worsen mortality risk. The bone deficits occurring after SCI are
precipitated by the central nervous system (CNS) insult and the subsequent musculoskeletal unloading, which
has resulted in an emphasis on activity-based physical therapy (ABPT) modalities that reload the impaired
limbs to restore bone integrity. Strategies that couple ABPT with electrical stimulation [e.g., functional electrical
stimulation (FES) cycling] are intriguing because they improve muscle recovery in the impaired limbs by
stimulating muscles to perform task-specific exercise and may promote sensorimotor recovery in the presence
of some spared spinal tracts. However, the ability of FES cycling to restore bone mineral density (BMD) in the
paralyzed limbs remains contentious after SCI, especially at the distal femur and proximal tibia sites that are
most prone to fracture. These data indicate need to optimize FES parameters for bone restoration. The goal of
this proposal is to develop and operationalize the first-ever ‘humanized’ FES bicycle system for rats. We will
then use our system in future proposals to optimize FES parameters for bone recovery in a ‘high-throughput’
manner, using our rat severe SCI model that exhibits similar musculoskeletal pathophysiology to persons with
severe traumatic SCI. To achieve our goal, we propose a novel high-risk / high-reward approach that will
reverse-translate the design of a human FES bicycle to develop a FES system for rats consisting of 1) a rat
bicycle that allows both FES directed and motorized pedaling on a crank shaft with modifiable resistance
levels, 2) sensors that record pedal locations, torque, velocity and that provide real-time feedback on these
pedaling parameters to a FES control system and a camera that records limb motions, and 3) a closed-loop
switched control system that accurately regulates pedaling between FES, in positions where muscles
contribute to pedaling, and an electrical motor coupled to the bicycle crank shaft that initiates in FES “dead
zones” where muscle activity provides little pedaling contribution. Our approach is innovative because, if
successful, it will provide a cost-effective and time-efficient means to optimize preclinical FES parameters for
bone restoration, which can then be fast-tracked to clinical trials that will assist in developing personalized
rehabilitation strategies for Veterans with SCI. To ensure our success, we have taken key steps, including: 1)
constructing a motorized (passive) rat bicycle that serves as the platform for our hybrid FES directed /
motorized cycle, 2) developing a closed-loop switched control system for human FES cycles that serves as a
model for our control system, and 3) characterizing the locomotor, bone, and muscle deficits in our rat severe
contusion SCI model, which we will use to test and validate the F...

## Key facts

- **NIH application ID:** 10840779
- **Project number:** 5I21RX003757-03
- **Recipient organization:** VETERANS HEALTH ADMINISTRATION
- **Principal Investigator:** Joshua F. Yarrow
- **Activity code:** I21 (R01, R21, SBIR, etc.)
- **Funding institute:** VA
- **Fiscal year:** 2024
- **Award amount:** —
- **Award type:** 5
- **Project period:** 2022-02-01 → 2024-09-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10840779

## Citation

> US National Institutes of Health, RePORTER application 10840779, Development and Validation of a Rodent FES Bicycle System (5I21RX003757-03). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10840779. Licensed CC0.

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