A method for estimating physical working capacity at the fatigue threshold (PWCFT)

Herbert A. Devries, Michael W. Tichy, Terry J. Housh, Kenneth D. Smyth, Anna Mae Tichy, Dona J. Housh

Research output: Contribution to journalArticlepeer-review

78 Scopus citations


Presently available tests of physical working capacity (PWC) such as VO2max and critical power may not be appropriate for unfit subjects because they require maximal or supramaximal workloads. Therefore, the purpose of this study was to evaluate a submaximal discontinuous incremental bicycle ergometer test (PWCFT) with an end point (fatigue threshold) determined by recording electromyographic (EMG) fatigue curves in the quadriceps muscle. The fatigue threshold was defined as the lowest workload producing a slope of the EMG voltage-time relation that was significantly different from zero slope at p<0.05 (single tail). The test-re-test reproducibility of PWCFT (n=17 subjects) was found to be r = 0.947, with no significant difference between trials. Thirty-two healthy male subjects aged 18-29 (mean 23-4 ± 31 years) whose fitness levels ranged from highly trained to untrained sedentary level were tested for PWCFT, lactate threshold (OBLA), percentage heart rate range at PWCFT (%HRR), and heart rate-workload relation (HR-WL). Stepwise multiple regression resulted in R = 0.833 with %HRR accounting for 40.7%, OBLA for 22.8% and HR-WL for 5.9% of the total variance. In addition, 12 subjects performed critical power (CP) testing. PWCFT and CP were correlated at r=0.670 with no significant difference p<005) between the means for the two methods. The results of this study indicated that the PWCFT test was objective, valid and highly reproducible and particularly useful for evaluating the PWCFT of unfit subjects.

Original languageEnglish (US)
Pages (from-to)1195-1204
Number of pages10
Issue number8
StatePublished - Aug 1987
Externally publishedYes


  • EMG fatigue curves
  • Fatigue threshold
  • Physical working capacity

ASJC Scopus subject areas

  • Human Factors and Ergonomics
  • Physical Therapy, Sports Therapy and Rehabilitation


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