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Muscle Health Monitoring
This project addresses the challenge of ineffective training often stemming from unbalanced exercise loads, leading to injuries or suboptimal results. We aim to develop a system for real-time monitoring of muscle health to guide users towards their optimal training intensity, thereby reducing injury risk and enhancing workout efficiency.
Our approach focuses on tracking two key biomarkers present in interstitial fluid (ISF): lactate and pH levels. ISF offers a non-invasive and accessible medium for monitoring, with lactate concentrations closely mirroring those in blood, making it ideal for wearable applications. While both lactate (increasing with work intensity) and pH (decreasing with output power) individually indicate muscle fatigue, their combined analysis allows us to account for complex biological pathways and achieve greater accuracy in assessing muscle state.
For effective pH sensing, we identified the critical requirement for the sensor's linear range to align with the physiological pH range of ISF (6 to 8). Based on observed variations during exercise, the sensor necessitates optimal sensitivity around 59 mV/pH unit and high stability, with deviations maintained below 1% over a 24-hour operational lifespan to ensure consistent and precise readings.
In the case of lactate sensing, while blood lactate levels during exercise can range from 0 to 10 mM, our application focuses on tracking the anaerobic threshold. This allows for a less stringent sensitivity requirement, aligning with average state-of-the-art performance around 50 µA/mM/cm². Crucially, the limit of detection (LOD) must be below 10 µM to ensure sensitivity to low lactate concentrations and minimize the impact of noise on measurement accuracy. Furthermore, the sensor's stability should maintain deviations below 5% for reliable performance. The operational lifetime for both sensors is designed to accommodate extended training sessions.
Leveraging existing advancements in biosensing technologies, we explored the state-of-the-art in lactate and pH detection. Microneedle arrays and single-needle approaches have demonstrated efficiency for non-invasive and precise lactate monitoring in ISF, showing strong compatibility with wearable form factors for real-time exercise tracking. While current market solutions like IDRO utilize sweat for lactate monitoring, ISF presents a more direct and potentially reliable medium for our application. Similarly, potentiometric pH sensing has shown significant promise in sweat analysis. Building upon these foundations, our project proposes the adaptation and integration of these sensing methodologies for simultaneous and continuous monitoring of lactate and pH levels in ISF, paving the way for personalized and optimized training regimens.