Interference of strength development by simultaneously training for strength and endurance

The purpose of this study was to determine how individuals adapt to a combination of strength and endurance training as compared to the adaptations produced by either strength or endurance training separately. There were three exercise groups: a strength group (S) that exercised 30--40 min . day-1, 5 days . week-1, and endurance group (E) that exercised 40 min . day-1, 6 days . week-1; and an S and E group that performed the same daily exercise regimens as the S and E groups. After 10 weeks of training, VO2max increased approx. 25% when measured during bicycle exercise and 20% when measured during treadmill exercise in both E, and S and E groups. No increase in VO2max was observed in the S group. There was a consistent rate of development of leg-strength by the S group throughout the training, whereas the E group did not show any appreciable gains in strength. The rate of strength improvement by the S and E group was similar to the S group for the first 7 weeks of training, but subsequently leveled off and declined during the 9th and 10th weeks. These findings demonstrate that simultaneously training for S and E will result in a reduced capacity to develop strength, but will not affect the magnitude of increase in VO2max.