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Using Moxy for critical power and time to exhaustion during cycling

An article published in the Journal of Applied Physiology on April 29th shed light on some critical applications for the use of near-infrared spectroscopy (NIRS) in endurance sport – The Balance of Muscle Oxygen Supply and Demand Reveals Critical Metabolic Rate and Predicts Time to Exhaustion

Using Moxy Monitor the authors tested the hypothesis that:

"%SmO2 distinguishes sustainable from unsustainable work rate and predicts time to exhaustion"

The researchers showed:

  • Negative slope of %SmO2 was present during non-sustainable exercise (above critical power) and positive slope was present during sustainable exercise intensity.

Application: This means that if %SmO2 is continually decreasing during exercise there is a finite amount of time that exercise intensity can be sustained.

  • Depletion and repletion of work completed above Critical Power (%D’) could be measured second-by-second to accurately predict time to exhaustion.

Application: The amount of time exercise can be sustained while %SmO2 is decreasing can be accurately measured and predicted which could help with pacing strategies during races or training.

Justification: The authors chose to use Moxy due to "because of its specificity to muscle tissue, its wireless capability/lack of subject interference during exercise (particularly running), and its high repeatability, reproducibility, dynamic range and face validity to venous O2"

This article builds on previous literature that shows that the balance between oxygen delivery and utilization measured via NIRS is a key marker for the prediction of task failure during endurance exercise. It further associates SmO2 as a valuable training and racing tool and lends credence to the use of NIRS for monitoring endurance performance in real-time, although more studies need to be completed to confirm the efficacy of these measurements across different sporting applications.

For other articles relating SmO2 to task failure and sport application please see:

Muscle oxygen dynamics in elite climbers during finger-hang tests at varying intensities

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