Full-Time Work Tolerance: Achieving an Accurate Calculation | webFCE

Full-Time Work Tolerance: Achieving an Accurate Calculation

construction worker does work full-time work tolerance

One critical function of an FCE is to evaluate an individual’s full-time work tolerance: their ability to work a full 8-hour day. The 8-hour work prediction from a period of testing is essential, and the determination should not be observational. FCEs that do not use scientific work physiology formulas to predict ability to work eight hours lack validity1,2.

FCEs Need Definitive Work Physiology Formulas

The Commission on Accreditation of Rehabilitation Facilities (CARF) notes the need for definitive work physiology protocols, as well as promotion for a uniform standard of FCE service. They also conclude that most FCEs suffer from a lack of objective data. Therefore, they can not accurately predict a worker’s success in actual full-time job-related functions. Rather, FCEs must project data for the examinee’s ability to work (or attempt to work) an eight-hour period without professional knowledge or expertise.

In accordance with this research, WebFCE’s functional capacity evaluation does incorporate definitive work physiology formulas. This allows our FCE to accurately calculate and predict an individual’s full-time work tolerance.

Heart Rate and Work Physiology Principles

There is much confusion about terms such as aerobic capacity and physical work capacity. Basic work physiology principles are important factors for predicting an individual’s ability to tolerate full time work. The use of heart rate has been widely accepted as an industrial physiological measurement. It is easy to administer and interpret, therefore aiding accuracy; it also has a linear relationship with energy expenditure. Examiners can measure heart rate without interfering with the work task being performed.

Research also deems heart rate the best index for measuring physical work. This is because heart rate is reasonably similar for all persons during the performance of work. With any given person, a linear relationship also exists between oxygen consumption (energy expenditure) and heart rate.

Determining Efficiency, Tolerance, and Limits

In order to determine the correct burden an individual can bear during an 8-hour work period, one must first calculate several factors:

  • The individual’s efficiency of physiological work
  • Their full-time work tolerance
  • Their limit of continuous work

The efficiency of physiological work is defined as the percentage of energy that is transformed into useful, sustainable work. Full-time work tolerance is achieved when steady work efficiency and the work physiological response (heart rate) have parallel linear responses. The limit of continuous work is the sustainable work level that has a linear physiological response and can be maintained without excessive fatigue.

If the burden placed on a worker is too high in relation to their capacity for sustained physical work, they will become fatigued. Therefore, the closer the task is to a worker’s maximum capacity, the shorter the length of time they will be able to work productively and safely.

Accordingly, Jiang, Kodak and NIOSH3-5 recommend intensities for an 8 hour shift do not exceed 33% of a worker’s capacity. In other words, a person working an eight hour work day should be able to maintain a maximum work load of 33% (or less) of their VO2 max (aerobic capacity) without fatigue.

One can use work physiology formulas to estimate a worker’s maximum heart rate in relation to the percentage of aerobic capacity. One can also apply the formula to work prediction for the process of providing a definitive analysis of calculating full time work.

Schedule a demo today to see how WebFCE’s fast, comprehensive, and straightforward process delivers these accurate results.


  1. Becker TJ, Morrill JM, Stamper EE. Applications of work physiology Science to Capacity Test Prediction – Full time Work – 8 Hour Work day. Journal of the International Association of Rehabilitation Professionals, November 2008, The Rehabilitation Professional; 15(4):45-56.
  2. Becker TJ. Functional capacity evaluations: the work physiology component for predicting full time work. Directions in Rehabilitation Counseling, 2007;18(16):177-186.
  3. Jiang B. Psychophysical capacity modeling of individual and combined manual materials handling. Lubbock, Tex: Texas Tech University; 1984.
  4. Kodak Ergonomics Group, Ergonomic design for people at work. New York: Van Nostrand Reinhold; 1986.
  5. Astrand P, Rohdahl K, Dahl H, et al. Textbook of Work Physiology. Champaign Ill: Human Kinetics; 2003.