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The best Fatigue Management Tool based on IFLS

By tapping on Info the app displays this website. (If internet connection available) This webpage will explain the calculations behind the used Fatigue Model and provides additional information about Stone Productions.

The Fatigue Model Calculations consist of the base model IFLS calculations (which is based on the model developed by the University of South Australia) with special add ons (such as Fatigueing Activity Factor and Outside Circadian Rhythm Corrections, developed by Stone Productions).

The IFLS is the sum of 3 applied rules:

Rule 1; the amount of Sleep prior 24 hours:

R1-Factor x amount of hours below a certain threshold. Most FRMS use the minimum threshold of 5 hrs. Sometimes 6 hrs is used. Some FRMS limit the max score to a certain limit (e.g. 12). On the Parameters screen the Score 0 Hour = Threshold value can be set to either 5 or 6. The Max Score for this factor can also be set. The screen will show a row of hours sleep in Prior 24 hrs and below that the corresponding score for this factor.

Rule 2; the amount of Sleep prior 48 hours:

R2-Factor x amount of hours below a certain threshold. Most FRMS use the minimum threshold of 12 hrs for this factor. This Score 0 Hour value can be set from 10 to 14 hours. Also for this factor the Max Score can be set on the Fatigue Model Parameters screen. The screen will show a row of hours sleep in Prior 48 hrs and below that the corresponding score for this factor.

Rule 3; the amount of hours since last (significant) sleep > Sleep prior 48 hours:

R3-Factor x the surplus of hours awake in comparison to the amount of sleep prior 48 hours. [ If hours awake is larger than the amount of sleep prior 48 hours than the factor is calculated as; R3-Factor x the difference between the amount of sleep prior 48 hrs and the amount of hours awake since last (significant) sleep. ]

Some FRMS formulate the requirement for a significant sleep. This is based on the assumption that a sleep can only be effective when going thru multiple phases of sleep. This App can accommodate such a requirement by setting the Awake Count Reset. By setting this value to a higher value than 1, the calculation of the hours awake will continue until a period of consecutive sleep is entered equal to this ‘Awake Count Reset’ value. [ So you can set the amount of hours of sleep that is required to get a significant sleep. ]

This App offers another way of manipulating this factor. By setting Fatiguing Activity to other than 1.0 it will count every hour nominated as a fatiguing activity equal to this factor. For example if a period of 2 hours is nominated as a fatiguing activity (by tapping Fat Act after a selection on the Activities/IFLS screen) and the ‘Fatiguing Activity’ factor is set to 2.0 (on the Parameters screen) the App will calculate 4 hours awake for this 2 hour period.

Outside Circadian Rhythm Correction; effectivity of sleep outside circadian rhythm;

The App will look at the regularity of the sleep pattern. It will determine for a Sleep activity in any hour of the natural day if Sleep occured at the same hour of the day in the previous R amount of days. If that was the case minimal C times in these previous R days then the amount of sleep added to X and Y = 1 (full effective sleep). If this is not the case then the amount of sleep added to X and Y = OSCRF (Outside Circadian Rhythm Correction Factor).

The IFLS is the sum of the 3 rule calculations:

Rule1 = (T - X) x R1-Factor

* [ If Rule1 > Max Score then Rule1 = Max Score (prior 24) ]

X = sum of (Sleep x OSCRCF) prior 24 hours

T = threshold value for sleep prior 24 hours (5 or 6)

* [ If (T - X) < 0 => Rule1 = 0 ]

* [ base setting for R1-Factor = 4 ]

Rule2 = (F - Y) x R2-Factor

* [ If Rule2 > Max Score then Rule1 = Max Score (prior 48) ]

Y = sum of (Sleep x OSCRCF) prior 48 hours

F = threshold value for sleep prior 48 hours (10 ~ 14)

* [ If (F - Y) < 0 => Rule2 = 0 ]

* [ base setting for R2-Factor = 2 ]

Rule3 = (Z - Y) x R3-Factor

Z = sum of hours awake since last [significant] sleep

* [ if Fat Act => awake = Fat Act Factor ]

* [ If (Z - Y) < 0 => Rule2 = 0 ]

* [ base setting for R3-Factor = 1 ]

IFLS = Rule1 + Rule2 + Rule3

* [ If Outside Circadian Rhythm Correction is not applied OSCRCF always = 1 ]

* [ If Sleep is repeated minimal C times previous R days at the same hour of natural day => OSCRF = 1 (otherwise as set by Outside C.R. Factor)