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

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Abstract
Presently available tests of physical working capacity (PWC) such as [Vdot]O2max 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 pFT (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 pFT test was objective, valid and highly reproducible and particularly useful for evaluating the PWCFT of unfit subjects.