Effects of muscle damage indicators and antioxidant capacity after interval training on the 800-m records of adolescent middle-distance runners

To examine the effect of 10-week interval training (IT) at varying intensi-ties on serum muscle damage indicators and antioxidant capacity and determine its effect on the 800-m records of adolescent middle-dis-tance runners. Twenty male high-school middle-distance runners were randomized between the high-intensity IT (HIIT; n= 10) and the medi-um-intensity IT (MIIT; n= 10) groups. Three sessions/week for 10 weeks (total of 30 sessions) were performed; one session of IT was for 60 min. The high and medium exercise intensities were set at 90%-95% and 60%-70% heart rate reserve (HRR), respectively. Intensity at rest was 40% HRR for both groups. Weight training was performed at 60%-70% of one repetition maximum for two sessions/week. The changes in se-rum muscle damage indicators and antioxidant capacity in the two groups were measured, and their effects on the 800-m records were analyzed. The 10-week training reduced serum muscle damage indica- tors in middle-distance runners, but only the HIIT group displayed a de-crease in creatine kinase. For the change in antioxidant capacity, the two groups demonstrated no significant change in malondialdehyde (MDA), whereas the HIIT group exhibited a significant increase in super-oxide dismutase (SOD). IT also reduced the 800-m records in middle-dis-tance running, and the effect was stronger in the HIIT group. In conclu-sion, 10-week HIIT can have a positive effect on muscle damage indi-cators, showed a significant increase in SOD as a key indicator of anti-oxidant capacity, and improved the 800-m records in middle-distance runners.