European Journal of Applied Physiology

, Volume 119, Issue 7, pp 1633–1648 | Cite as

A novel approach for establishing fitness standards for occupational task performance

  • Jeffrey W. RyderEmail author
  • Paul Fullmer
  • Roxanne E. Buxton
  • J. Brent Crowell
  • Elizabeth Goetchius
  • Omar Bekdash
  • John K. DeWitt
  • Emma Y. Hwang
  • Alan Feiveson
  • Kirk L. English
  • Lori L. Ploutz-Snyder
Original Article



To identify strength and performance thresholds below which task performance is impaired.


A new weighted suit system was used to manipulate strength-to-body-weight ratio during the performance of simulated space explorations tasks. Statistical models were used to evaluate various measures of muscle strength and performance on their ability to predict the probability that subjects could complete the tasks in an acceptable amount of time. Thresholds were defined as the point of greatest change in probability per change in the predictor variable. For each task, median time was used to define the boundary between “acceptable” and “unacceptable” completion times.


Fitness thresholds for four space explorations tasks were identified using 23 physiological input variables. Area under receiver operator characteristic curves varied from a low of 0.68 to a high of 0.92.


An experimental analog for altering strength-to-body weight combined with a probability-based statistical model for success was suitable for identifying thresholds for task performance below which tasks could either not be completed or time to completion was unacceptably high. These results provide data for strength recommendations for exploration mission ambulatory task performance. Furthermore, the approach can be used to identify thresholds for other areas where occupationally relevant tasks vary considerably.


Strength Power Work Fitness Threshold Task 



The authors thank Tinh Trinh for engineering support, and Nichole Gadd and Galen Kreutzberg for test operator support. This work was supported by the National Aeronautics and Space Administration Human Research Program NNJ15HK11B.

Compliance with ethical standards

Conflict of interest

The authors report that they have no conflicts of interest.

Ethical standards

All experiments comply with the current laws of the United States, the country in which the experiments were performed.


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Copyright information

© This is a U.S. government work and its text is not subject to copyright protection in the United States; however, its text may be subject to foreign copyright protection 2019

Authors and Affiliations

  • Jeffrey W. Ryder
    • 1
    Email author
  • Paul Fullmer
    • 2
  • Roxanne E. Buxton
    • 3
  • J. Brent Crowell
    • 4
  • Elizabeth Goetchius
    • 3
  • Omar Bekdash
    • 1
  • John K. DeWitt
    • 1
  • Emma Y. Hwang
    • 1
  • Alan Feiveson
    • 5
  • Kirk L. English
    • 2
    • 6
  • Lori L. Ploutz-Snyder
    • 7
  1. 1.KBRwyle Science and SpaceHoustonUSA
  2. 2.Department of Clinical Health and Applied SciencesUniversity of Houston–Clear LakeHoustonUSA
  3. 3.Department of Health and Human PerformanceUniversity of HoustonHoustonUSA
  4. 4.MEI TechnologiesHoustonUSA
  5. 5.Biomedical Research and Environmental Sciences, National Aeronautics and Space AdministrationJohnson Space CenterHoustonUSA
  6. 6.Exercise and Nutritional Health InstituteUniversity of Houston–Clear LakeHoustonUSA
  7. 7.School of KinesiologyUniversity of MichiganAnn ArborUSA

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