Study aim: The purpose of this study was to examine the effects of a repeated sprint exercise protocol on muscle damage indicators, serum IGF-I and cortisol levels. Material and methods: Nine trained male subjects (age 23.3 ± 3.6 years) completed a repeated sprint protocol consisting of two sets of 10 × 30-m maximal sprints with 30 s of active recovery between sprints and 5 min of passive recovery between sets. The isometric strength and flexibility were measured before, immediately after and 24 hours after exercise. 30-m maximal sprint time was measured before and 24 hours after exercise. Blood samples were taken before, immediately after and 24 hours after exercise. Results: Isometric strength and flexibility were significantly decreased after exercise and 24 hours after exercise (p < 0.05). 30-m sprint time was significantly increased 24 hours after exercise (p < 0.05). A significant increase in serum lactate dehydrogenase, IGF-I and cortisol were found after exercise (p < 0.05). Serum creatine kinase increased significantly immediately after and 24 hours after exercise compared to pre-exercise values (p < 0.05). Conclusion: Our data show that due to increased serum IGF-I level, repeated sprint exercise may have anabolic effects as well as traumatic effects on the muscles.