Fatigue Assessment – Beta Version

Overview

The Rewire fatigue assessment system is designed to provide you with a convenient way to assess your daily level of mental and physical fatigue.   The system takes a holistic view, measuring your level of psychological, physiological and cognitive fatigue.   This system includes a cognitive reaction time test called a Simple Reaction Time Task (SRT).    The SRT is helpful for noticing even subtle declines in your focus and decision-making abilities due to mental fatigue.  The system also includes biometric monitoring via a heart rate strap which measures your resting heart rate and HRV.   If you enable the integration with Apple Health or Google Fit, the Rewire system will also incorporate your sleep data as an additional data point for your assessment.  Apple Health and Google Fit integration can be found in the app settings section.   Lastly, the fatigue assessment system will ask you a series of self-assessment questions.   These subjective questions were developed by Nasa for testing the readiness of astronauts.  The testing protocol is called the NASA Task Load Index (TLX).  

Note this product is still in beta testing and is likely to evolve based on athlete feedback and additional research

  

1. Fatigue Summary

The Fatigue Summary section provides an overview of the key metrics from your assessment compared to your baseline from previous tests.   Pay close attention to the number of lapses and misses from your cognitive test as this is a clear indicator of mental fatigue.   Additionally, any significant changes in your resting heart rate, HRV or level of sleep are worth paying attention to as these may indicate a change in your physical fatigue.

2. Fatigue Assessment Metrics

The following cognitive and physiological metrics are tracked as part of your assessment metrics:

  • Trained Reaction Time (TRT): TRT is the range of all responses from 100 milliseconds to 500 milliseconds and represents the reaction time that is improved upon with continual fatigue assessment testing.
  • Lapses (LT): Lapse time counts the total number of slower than average responses to brain training questions.  For the fatigue assessment system, lapses are counted for any response slower than 500 milliseconds for a reaction time question.  A higher than normal number of lapses is a good indicator of increased mental fatigue.
  • Misses (shown in fatigue summary): Misses are any failure to respond to a reaction time question lasting longer than 2 seconds.
  • Fastest Reaction Time: The fastest reaction time is the fastest response during the current fatigue assessment.  A trend arrow also appears to show any changes against your baseline from prior tests.   Note in this test, a fast reaction time is between 200 – 299 ms, an average between 300-399 ms and a slow reaction time between 400-499 ms.  Anything greater than 500ms is considered a lapse.   The fastest known reaction times have been achieved by Olympic sprinters at the start line when the gun goes off e.g. in the Rio Olympics Tori Bowie had a reaction time of 112 ms.  For context, anything lower than 90ms is considered a false start in track.   Additionally, humans tend to be faster at audio-based reaction time tests than visual tests.
  • Heart Rate (Average): Average heart rate measured in heartbeats per minute over the course of the workout and per interval.
  • HRV: Heart rate variability is the measure of the beat-to-beat variability between heartbeats.  Known as a very reliable measure of both physiological and psychological stress it is used as a standard metric for training across most sports.   Rewire uses the gold standard calculation for HRV known as rMSSD which stands for the root mean square of successive differences.  This is the same standard used by many well-known HRV apps and tools though it is useful to note that there is no standard for the scale factor applied to HRV which is why from app-to-app the measurements are slightly different.   You may also override the Rewire’s HRV calculation by syncing to Apple Health or Google Fit and selecting the “Use HRV data from this source” found under integration settings.  Read more about HRV measurements and the science behind it here.
  • Sleep (in Hrs):  Sleep measures the hours of sleep (not time in bed).  This data is currently pulled from Apple Health or Google Fit and is highly variable depending upon the accuracy of your sleep tracker.  Apple Health and Google Fit integration can be found in the app settings section

3. Self-Rated Subjective Metrics

Your Self-Rated Subjective metrics are very likely to be the most accurate indicators in your level of fatigue and physical and psychological readiness to perform.  These subjective questions were developed by Nasa for testing the readiness of astronauts.  The testing protocol is called the NASA Task Load Index (TLX).    The questions include:

  • Overall Subjective Score: Calculated by adding up the scores of all four numbers from self-rated questions.  Additionally, a trend arrow will show your current results as compared to your baseline.
  • Level of Rest:  Your self-assessment of your level of rest.  Generally, your first instinct is most accurate.   Note this is a positive scale as indicated by the orange bar from 0 to 100 with 0 signifying no rest and 100 the most amount of rest.
  • Level of Readiness: Your self-assessment of your level of readiness to perform.  Generally, your first instinct is most accurate.   Note this is a positive scale as indicated by the orange bar from 0 to 100 with 0 signifying not being ready to perform and 100 being the most ready to perform.
  • Level of Stress: Your self-assessment of your level of stress (both physical and psychological).  Generally, your first instinct is most accurate.   Note this is a negative scale as indicated from the red bar from 0 to -100 with 0 signifying the lowest level of stress and -100 the highest level of stress.
  • Level of Frustration: Your self-assessment of your level of frustration.  An increase in frustration is generally a strong indicator of cognitive fatigue.  Generally, your first instinct is most accurate.   Note this is a negative scale as indicated by the red bar from 0 to -100 with 0 signifying the lowest level of frustration and -100 the highest level of frustration.