In brief: The purpose of this study was to determine the energy cost of the elementary backstroke and to see if heart rate and perceived exertion are useful for monitoring exercise intensity. Five healthy men and five healthy women swam the elementary backstroke at four different intensities, and velocity, VO2, heart rate, and perceived exertion were monitored. Each dependent variable significantly increased with increasing intensity. The only sex difference was a higher Vo2in men for each work intensity. Average energy cost ranged from 0.097 kcal·kg−1·min−1at 1.1 to 1.4 km·hr−1to 0.17 kcal·kg−1·min−1at 1.8 to 2.0 km·hr−1(SEM±0.01). We concluded that the elementary backstroke is suitable for a fitness program.