# Development of Knitted Strain Sensor Optimized for Dumbbell Exercise and Evaluation of Its Electrical Characteristics

## TL;DR

Researchers created a knitted strain sensor for monitoring elbow angles during dumbbell exercises, showing it is sensitive, elastic, and durable for wearable fitness use.

## Contribution

A novel knitted strain sensor optimized for dumbbell exercise with high sensitivity and reliable performance under repeated stress.

## Key findings

- The sensor achieved a high gauge factor of 698, indicating excellent sensitivity.
- It demonstrated reliable performance after 100 repeated bending tests at various angles and speeds.
- The sensor showed fast responsiveness and good elasticity for potential use in wearable fitness or rehabilitation systems.

## Abstract

With growing interest in wearable technologies, the development of flexible sensors and products that can monitor the human body while being comfortable to wear is gaining momentum. While various textile-based strain sensors have been proposed, their implementation in practical, exercise-specific applications remains limited. In this study, we developed a knitted strain sensor that monitors elbow angles, focusing on dumbbell exercise, which is a basic exercise in sports, and verified its performance. The material of the developed knitted strain sensor with a plain stitch structure comprised a silver-coated nylon conductive yarn and an acrylic/wool blended yarn. To evaluate the electrical and physical characteristics of the developed sensor, a textile folding tester was used to conduct 100 repeated bending experiments at three angles of 30°, 60°, 90° and speeds of 10, 30, 60 cpm. The system demonstrated excellent elasticity, high sensitivity (gauge factor = 698), fast responsiveness, and reliable performance under repeated stress, indicating its potential for integration into wearable fitness or rehabilitation platforms.