Study aim: To determine the effects of 60- or 180-s rest intervals between sets of drop jump (DJ) exercise on serum creatine kinase (CK) activity and perceived muscle soreness.

Materials and methods: A group of 36 healthy male subjects aged 18 - 19 years performed 4 sets of 10 DJ, the rest intervals between sets amounting to 60 (Group A) or 180 s (Group B). Before, as well as 3, 24, 48, and 72 h post-exercise, blood was sampled for determining the activity of in serum CK activity and the perceived muscle soreness was reported. Two-way ANOVA (time x rest interval) was used in data analysis.

Results: The DJ sessions induced muscle soreness and elevated serum CK activity (p<0.05). No significant between-group differences were found.

Conclusion: Rest intervals of 1 - 2 min duration had no effect on the magnitude of changes in CK activity or perceived muscle soreness. This may be of practical importance when designing training which includes drop jumps.