The objective of this study to examine the effects of submaximal exercise in crawl swimming with a controlled breathing frequency on some biochemical characteristics, aerobic capacity and the performance of the young swimmers.Among 100 volunteers from university students who hand swimming skills, 38 students were randomly selected and divided into two experimental and control groups. Both groups underwent an 8 weeks training program, including three session per week and 1½ hours in each session. In average, the intensity of the exercise was set 60% HR reserve. In the experimental group, subjects were asked to control their breathing frequency (2-6 strokes between two consequent breathing maneuvers increasingly) during swimming. While, the control group were asked to breath as usual (one breathing maneuvers in each stroke). Before and after the experiment, the subject’s' blood samples were examined to measure PO2, PCO2, PH, HCO3, %SO2 and CPK and LDH enzymes.VO2-max and swimming record were tested with Astrand field submax test and chronometer, respectively.Results showed that in the experimental group, PCOz, CPK, LDH and VO2 max were significantly (p<0.05) increased by %6, %38, %56 and %23 respectively. Also, the experimental group showed a better speed (% 12 faster) in 30m distance swimming than the control group. In conclusion the interval swimming exercise with controlled breathing frequency may increase both aerobic and anaerobic capacities of swimmers and may lead them to a better performance.