Ergoniza Intelligent

Discomfort: calculation options

This dialog configures criteria used to calculate Postural discomfort. Open it with the options button at the bottom of Postural load: Discomfort.

The options determine whether the displayed result is relative to posture duration or absolute, and whether upper-limb orientation relative to gravity is considered.

Discomfort calculation options
No. Control Function
1 Time-relative Includes posture sustainment or exposure time in the discomfort calculation.
2 Consider gravity Includes the favorable effect of gravity in certain upper-limb postures.
3 Gravity-effect intensity Adjusts the maximum intensity of the gravity correction.

Purpose of the dialog

Postural discomfort can be displayed using different criteria.

An absolute value provides a common reference for a posture sustained for a standard duration. A time-relative value incorporates actual sustainment or exposure time. In addition, some upper-limb orientations allow gravity to assist the posture, reducing perceived postural demand.

This dialog controls both aspects.

Time-relative

Time-relative, identified by number 1, includes posture sustainment or exposure time.

When enabled

The displayed value is adapted to the posture’s or activity’s actual temporal context rather than being limited to the 60-second reference:

  • in Single posture mode, it depends on Action duration and repetitiveness;
  • in Multiple postures mode, it depends on sustainment or exposure time in the displayed sequence and, when Include repetitions and rest periods is enabled, on projection of the activity over successive repetitions.

The same posture can therefore produce different values when it occurs momentarily, is sustained, appears at different activity times, or belongs to a repeated activity.

When disabled

Discomfort is calculated relative to absolute postural discomfort.

In Ergoniza Intelligent, this is the discomfort associated with sustaining the posture for 60 seconds. It provides a normalized reference for comparing postures without directly including different durations.

Use it to:

  • compare postures using the same temporal reference;
  • view a posture’s intrinsic discomfort;
  • prevent duration or repetition from changing the displayed result.

Conceptual difference

  • With Time-relative disabled, the result is an absolute 60-second reference.
  • With it enabled, the system adapts the value to actual exposure time.

Use time-relative values for realistic work context and absolute values when postures must be compared on a common basis.

Relationship with activity repetitions and rest

In Multiple postures mode, Time-relative and Include repetitions and rest periods under Activity repetitions affect different aspects.

Time-relative adapts discomfort to sustainment or exposure within the displayed activity. A posture sustained for several seconds can therefore show increasing discomfort even without additional repetitions.

Include repetitions and rest periods projects the displayed activity as a cycle repeated with rest between repetitions. Disabling it does not remove temporal effects from the base sequence while Time-relative remains enabled; it only stops considering successive cycles and intercycle rest.

For example, Time-relative can increase discomfort while a posture is sustained in the base sequence. Including repetitions and rest can additionally incorporate prior cycles, recovery, and temporal fatigue decay.

How discomfort develops over time

With time-relative calculation, the system combines the posture’s momentary value with its development as sustainment or exposure increases.

In simplified terms:

  • for very short times, the result approaches momentary discomfort;
  • as time increases, it moves toward the 60-second reference;
  • at longer exposures, it can continue increasing according to the system’s temporal model.

This is particularly relevant to sustained tasks and sequences containing sustained postural patterns. With repetitions and rest enabled, the analysis can also project successive repetitions.

For methodological details, see:

Consider gravity

Consider gravity, identified by number 2, includes gravity’s favorable effect on certain upper-limb postures.

It affects upper-arm and forearm discomfort when spatial orientation allows gravity to partially relieve postural demand.

Meaning of gravity-assisted

A posture is more favorable when the upper arm or forearm is oriented closer to hanging downward in the direction of gravity.

For example:

  • an upper arm near downward vertical can be less demanding than an elevated upper arm;
  • a downward-hanging forearm can be less demanding than a horizontal or elevated forearm.

The system then applies a favorable correction. It never increases discomfort; it can only reduce it when upper-limb orientation is mechanically favorable.

Affected movements

The gravity correction primarily applies to:

  • the upper arm, in its main spatial components;
  • the forearm, especially elbow flexion-extension.

It is not a general correction for every movement or body segment.

Effect of trunk posture

For the upper arm, the correction also depends on trunk orientation. Mechanical advantage depends on both upper-arm angle and overall body position.

The gravity correction is therefore a modulation based on spatial posture rather than a fixed adjustment.

Gravity-effect intensity

Control 3 sets the maximum intensity of the gravity correction:

  • Very low (50%)
  • Low (60%)
  • Medium (70%)
  • High (80%)
  • Very high (90%)

This is not a discomfort percentage. It is the maximum weighting given to gravity’s correction.

Lower values make the correction gentler; higher values produce a stronger reduction when the posture is gravity-assisted.

This selector has an effect only while Consider gravity is enabled.

When to enable the options

Time-relative

Keep it enabled when:

  • discomfort should reflect actual posture duration;
  • sustained or repetitive tasks are analyzed;
  • the result should represent actual exposure.

Disable it when:

  • comparing postures under one temporal reference;
  • examining absolute posture discomfort.

Consider gravity

Keep it enabled when:

  • upper-limb discomfort should be more realistically represented;
  • gravity can assist upper-arm or forearm posture;
  • this spatial effect should be included.

Disable it when:

  • a more conservative reading is desired;
  • results should be compared without the correction;
  • the specific effect of gravity is being examined.

Recommendations for use

  1. Keep Time-relative enabled for exposure-dependent results.
  2. Disable it for the 60-second absolute discomfort reference.
  3. Keep Consider gravity enabled for a more realistic upper-limb estimate.
  4. Select the correction intensity appropriate to the intended gravity influence.
  5. Use the same configuration when comparing alternatives.

Relationship with the Technical foundations

For methodological details, see:

These sections explain absolute discomfort, the transition from momentary to time-dependent discomfort, and the gravity correction for the upper limb.