Physical fatigue and the perception of differences in load: a signal detection approach.

Workload is an important factor related to perception of physical fatigue. Because a person engaged in physical activity eventually leading to painful exhaustion is in a pay-off situation, the paradigm of signal detection might be applicable to the perception of differences in load. Two male track and field athletes, aged 22 and 24 yr., participated in two experiments. In Exp. 1 difference threshold were determined with 25%, 50%, 60%, 65% and 70% of VO2 max as basic loads on a bicycle ergometer. Results showed a decreasing k over increasing work loads, contrary to Weber's law. In Exp. 2 a non-parametric signal detection procedure was used, with 25%, 40%, 50% and 60% of VO2 max as noise levels and a signal intensity of 1.5 watt in every condition. A chi 2 test for a 2-factor design showed only an effect of noise level. The converging results of both experiments led to the conclusion of a relative increasing sensitivity across increasing work loads. The main goal for future research will be to develop the signal detection method as a framework for research on fatigue.