I am going to put this out there and be up front right away, I am not a fan of performance testing when it comes to fatigue management.  Yes, I know many regulations require it and many best practices and guidelines recommend it.  But, I think that, if one of the goals of fatigue risk management is to prevent negative outcomes, testing a person’s performance is too far down the line.  Plus, performance testing cannot be used without an assessment of fatigue risk or levels and is redundant.  Let me explain…

…Testing performance with tools such as a psychomotor vigilance task (PVT), a digit-symbol substitution test (DSST) or a Stroop task will most definitely show impairments when fatigue reaches an influential level.  At this point it is too late, you are too far down the line because a negative outcome has already occurred, that is, performance has already been impaired.  In other words, the goal of preventing negative outcomes has been missed and we have not even determined if fatigue played a role in the impaired performance.

Although, PVT’s, DSST’s and Stroop tasks are sensitive to sleep-related fatigue, that is, results on these tests reliably declines in fatigued people, poor performance on these tasks does not mean a person is experiencing sleep-related fatigue.  Performance on these tasks can also be affected by mental fatigue, physical fatigue, extremely cold environments, distraction[1], symptoms of depression[2][3], age, effort, meal timing[4], and traumatic brain injuries[5].  Plus, when these performance testing tools are translated into Smart phone Apps, there is a risk that they may compete with other Apps for the phone’s resources which can impact the test’s results.  To accurately state that a person’s performance on one of these tasks is impaired by sleep-related fatigue, you would have to rule out the influence of all other potential explanations for the impaired performance.  In a research setting this may be possible, but in an operational setting, it is not practical.  Instead, all that is measured is fatigue risk or levels and a big assumption is used to link the impaired performance to fatigue.  Without measuring fatigue or estimating its risk, making the link is not possible.  In this sense, performance testing cannot be used without an assessment of sleep-related fatigue.

The need to link performance to fatigue is probably why all regulations, best practices and guidelines that include testing for fatigue-related performance impairments, also include assessing a person’s fatigue risk or fatigue level.  For example, there is often a requirement to assess sleep-related fatigue prior to starting a duty.  Fatigue levels can be measured subjectively by using the Karolinksa Sleepiness Scale (KSS) and fatigue risk can be assessed objectively by examining a person’s sleep-wake pattern leading up to the duty for fatigue risk factors such as:

1. Acute sleep disruption
2. Chronic sleep disruption
3. Continuous wakefulness
4. Circadian rhythm effects

The KSS, if answered honestly, or looking into the presence and magnitude of fatigue risk factors, can give you an accurate assessment of whether or not someone is fatigued or is at risk of being fatigued.  If fatigue is present or there is a risk of fatigue, action should be taken.  We don’t need to confirm that some aspect of performance has been compromised to justify taking action.  In other words, performance testing is redundant.  We already know the person is fatigued or is at risk of being so, and since we also know that fatigue reliably decreases performance, we should take action.  Testing performance is not giving us any new information.

Now that you know why I am not a fan of performance testing in the context of fatigue management, hopefully, you will avoid it if you can.  If you cannot avoid it, one of my favourite Smart phone performance testing Apps is the PVT Research Tool by Texas A & M University System CSE.  It is a FREE and simple App that allows users to share their results in a detailed spreadsheet with whomever they wish.  Below is what the App looks like on the Apple App Store and here is the link: https://apps.apple.com/us/app/pvt-research-tool/id1475726298

References:

[1] PVT and distraction:  Rupp, T. (2013). Concepts of fatigue, sleepiness, and alertness.  In C. Kushida (Ed.), Encyclopedia of Sleep, Elsevier Inc., pp. 24-26.

[2] PVT and depressive symptomology:  Plante, D., Hagen, E., Ravelo, L., & Peppard, P. (2020). Impaired neurobehavioral alertness quantified by the psychomotor vigilance task is associated with depression in the Wisconsin Sleep Cohort study.  Sleep Medicine, 67, 66-70.

[3] DSST and depressive symptomology: Jaeger, J. (2018).  Digit symbol substitution test: The case for sensitivity over specificity in neuropsychological testing.  Journal of Clinical Psychopharmacology, 38(5), 513-519.

[4] DSST and PVT and meal timing: Grant, C., Dorrian, J., Coates, A., Pajcin, M.,  Kennaway, D., Wittert, G., Heilbronn, l., Vedova, C., Gupta, C., & Banks, S. (2017).  The impact of meal timing on performance, sleepiness, gastric upset, and hunger during simulated night shift. Industrial Health, 55(5), 423-436.

[5] Stroop test and traumatic brain injury:  Ben-David, B., Nguyen, L., & van Lieshout, P.  (2011).   Stroop effects in persons with traumatic brain injury: selective attention, speed of processing, or color-naming? A meta-analysis.  Journal of the International Neuropsychological Society, 17(2), 354-363.