Optical Muscle Activity Measurement for Motion Artifact Control
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Solution Overview
Problem
Existing muscle activity monitoring technologies are inconvenient, uncomfortable, prone to noise and motion artifacts, and not suitable for long-term, everyday use, limiting the effectiveness of rehabilitation and assistive robotic systems.
Innovation Solution
A muscle activity measurement system using multiple illumination sources with different wavelengths, coupled to a wearable structure, measures optical responses from subcutaneous structures to detect muscle activity patterns, incorporating signal conditioning and motion sensing for accurate and comfortable long-term monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If surface electromyography (EMG) electrodes are used to measure muscle activation, then muscle activity can be measured noninvasively, but the electrodes are inconvenient to apply, uncomfortable to wear for extended periods, and susceptible to motion artifacts and electromagnetic noise
Solution Approach 1:
The patent replaces the mechanical/electrical contact-based EMG electrodes with an optical measurement system using near-infrared light. The system uses photodetectors to detect optical signals from muscle tissue, eliminating the need for skin-adhered electrodes and their associated discomfort and artifact problems while maintaining muscle activity measurement capability
Solution Approach 2:
The patent introduces near-infrared light as an intermediary to measure muscle activity. Instead of directly contacting muscle tissue with electrodes, the system uses optical signals that penetrate tissue and are modulated by muscle contraction, providing a non-contact measurement pathway that avoids electrode discomfort and artifact issues
2Ease of operation
If near-infrared spectroscopy (NIRS) probes are used to detect muscle activity, then muscle activity can be measured through optical response, but the probes are affected by motion artifacts and signal attenuation from subcutaneous adipose tissue
Solution Approach 1:
The patent uses multiple light sources with different wavelengths to penetrate tissue at different depths and overcome signal attenuation. By varying the wavelength parameter, the system can select optimal penetration depths that bypass subcutaneous adipose tissue and reach the muscle layer, improving signal accuracy while maintaining comfort
Solution Approach 2:
The patent incorporates motion sensors to detect body movement and uses this feedback to compensate for motion artifacts in the optical measurements. The system dynamically adjusts or filters measurements based on motion detection, maintaining measurement precision even when the patient moves during rehabilitation exercises
3Ease of operation
If textile electrodes embedded in tight-fitting garments are used, then some electrode comfort issues are overcome, but the reliability of signals has not yet matched conventional electrodes
Solution Approach 1:
The patent replaces textile electrodes with a purely optical measurement system. By using near-infrared light to detect muscle activity without electrical contact, the system eliminates the signal reliability issues of textile electrodes while maintaining the comfort benefits of wearable garments
4Measurement precision
If mechanical myography or musculoskeletal sonography are used to evaluate muscle activity, then muscle movement can be detected, but the methods lack spatial resolution or require expensive, large equipment
Solution Approach 1:
The patent replaces complex mechanical and ultrasonic imaging systems with a simple optical measurement system. By using near-infrared light and photodetectors, the system achieves muscle activity detection without requiring expensive, large equipment like ultrasound machines or MRI scanners, while providing sufficient spatial resolution for rehabilitation monitoring
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables continuous, unobtrusive monitoring of muscle activity patterns for rehabilitation and control of assistive robots, improving patient adherence to exercise programs and enabling more effective rehabilitation and daily task performance.
Implementation Method 1
near-infrared spectroscopy (NIRS) is employed to detect muscle activity. NIRS measurements capture changes in oxygen consumption and hemodynamics in human tissue. Since oxygen delivery and consumption in capillary beds indirectly reflects muscle activity, NIRS measurement data is indicative of muscle activity.
Implementation Method 2
A muscle activity measurement system includes multiple illumination sources having different emission wavelengths... measures optical responses from subcutaneous structures to detect muscle activity patterns
Data Source
AI summary
Methods and systems for determining changes in muscle activity patterns based on the optical response of subcutaneous human body structures are presented, along with methods and systems for controlling assistive robotic systems based on the measured muscle activity patterns. Elements of a muscle activity measurement system are mechanically coupled to a wearable structure that fits closely to a portion of the body of a human user. The muscle activity measurement system includes multiple emitters and detectors at different spacing along the skin surface. In some embodiments, the illumination intensity of each measurement channel, the programmable gain of each measurement channel, or both, are calibrated to maximize measurement sensitivity. In some embodiments, optical measurement data is employed to more accurately locate the muscle activity measurement system with respect to the human body. In some embodiments, a muscle activity measurement system tracks changes in muscle structure over time.