# Effect of Heavy Backpack Load Carriage on Acute Blood Flow, Nerve Conduction, Biomechanics and Dexterity of the Upper Limbs

> **NIH NIH SC3** · CALIFORNIA STATE UNIVERSITY SAN MARCOS · 2021 · $105,202

## Abstract

Project Summary
First responder, military, and law enforcement personnel regularly carry backpack loads of up to 60% body
weight. Use of the hands and fingers is often needed during or immediately after load carriage, but loads
applied via backpack straps can constrict blood flow and compress the brachial plexus nerves of the upper
limb. These factors can potentially lead to pain, injury and impaired use of the upper limbs. Understanding the
acute effects of heavy load carriage on upper limb physiology will aid development of field-based functional
measures to reduce the risk of injury and prevent long-term loss of hand function. Persons who regularly carry
heavy backpack loads for occupational purposes report incidences of pack palsy, a disability causing lack of
sensation and weakness in the hands. The proposed work aims to investigate relationships among
physiological changes, manual functional deficits during pack carriage, and pack palsy. It is unclear how the
magnitude and duration of backpack carriage affects acute changes in grip strength, pinch strength, manual
dexterity and light touch sensory threshold. The overall hypothesis is that walking with backpack load will
cause changes in upper limb blood flow, edema, and nerve conduction. Further, we expect these physiological
changes will result in measurable differences in manual dexterity, strength, and light touch sensory threshold
that will change with increasing load in the backpack and duration of time walking with load. To address the
hypotheses, I will determine the relative acute changes in upper limb blood flow, edema and nerve conduction
before and after walking with heavy backpack load. I will also identify quantitative changes in blood flow, grip
strength, pinch strength and manual dexterity at load levels of 15% and 30% body weight as compared to a
control condition. I will explore the effects of walking time with backpack load on upper limb blood flow and light
touch sensory threshold of the fingers which may be affected by nerve compression from backpack straps.
This much needed research will improve understanding of upper limb physiological and neuromuscular
changes with backpack carriage. The innovative methodology will allow study of multiple upper limb
physiological changes simultaneously. Increased understanding of backpack carriage could improve
prevention of brachial plexus injury and therefore reduce incidences of weakness or loss of hand function.
Application of this work could lead to early diagnosis of brachial plexus compression by means of functional
measures. Results of this work may improve hand function, injury prevention, and treatment of the upper
extremity for those who carry heavy backpacks in an occupational or recreational setting.

## Key facts

- **NIH application ID:** 10089137
- **Project number:** 1SC3GM139683-01
- **Recipient organization:** CALIFORNIA STATE UNIVERSITY SAN MARCOS
- **Principal Investigator:** Deanna J Schmidt
- **Activity code:** SC3 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $105,202
- **Award type:** 1
- **Project period:** 2021-04-19 → 2025-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10089137

## Citation

> US National Institutes of Health, RePORTER application 10089137, Effect of Heavy Backpack Load Carriage on Acute Blood Flow, Nerve Conduction, Biomechanics and Dexterity of the Upper Limbs (1SC3GM139683-01). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10089137. Licensed CC0.

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