Study aim: The aim of the study was to determine work performance in the aspect of work rate, energy, persistence, adaptation rate, and accuracy based on the indices of an athlete’s work curve. Material and methods: Thirty athletes (15 women and 15 men) who practised five sports (swimming, track and field, fencing, judo, and taekwondo) and a control group (30 university students, 15 women and 15 men) participated in a work curve test (Kraepelin). Both groups were equivalent. They were aged 18–25 years, all of them had finished secondary education, and studied at the same university. The analysis concerned indices grouped into 6 factors: quantitative measures of performance, measures of energy and persistence, measures of quick adaptation and efforts without self-restraint, measures of variability, measures of accuracy and diligence, and measures of additional factors. Results: Factor analysis of the work curve revealed a significant difference to the benefit of the athletes (p < 0.001) in the measures of energy and persistence. The results obtained in this study revealed good adaptation of athletes to exercise, resistance to fatigue, and quick process of learning. Conclusions: The results obtained may reflect the adaptation of athletes to long-term physical activity. Therefore, they are characterized by greater involvement and patience. Therefore, it can be concluded that monotonous training that necessitates much energy, concentration of attention, and endurance, and, consequently, high work performance, is one of the most important predictors of athletic activity.