The Effect of Rest Periods on Energy System Contribution During Interval Swimming

The purpose of this study was to investigate the effect of rest periods on energy system contribution during interval swimming and whether the energy system contribution varied depending on the swimmer’s specialty, such as swimmers who specialize in the 100 m or 200 m. Seven highly-trained male varsity swimmers performed three different tests: a 10-min continuous test (CON), 10 1min interval test with rest periods of 20 s (INT20) and 10 1-min interval test with rest periods of 30 s (INT30). Swimming velocity during all tests was set to maintain a blood lactate of 4 mM determined by progressive swimming. The relative aerobic and anaerobic energy system contribution was evaluated from accumulated oxygen uptake and oxygen deficit. Aerobic energy system contribution in CON, INT20, and INT30 was 93.3 ± 1.1, 81.0 ± 10.4, and 67.4 ± 8.5%, and anaerobic contribution was 6.7 ± 1.1, 19.0 ± 10.4, and 32.6 ± 8.5%, respectively. There were significant differences (p < .05) in both aerobic and anaerobic energy system contributions between each test. The index derived from the ratio of swimming velocity of the best time between 100 m and 200 m correlated significantly (p < .05) to relative anaerobic energy system contribution during INT30. These results suggest that the energy system contributions during interval swimming are significantly affected by the difference of 10 s in the rest periods, and the contributions would vary depending on the swimmer’s specialty.