Isoload vs isokinetic eccentric exercise: a direct comparison of exercise-induced muscle damage and repeated bout effect

Purpose: This study compared the exercise induced muscle damage and repeated bout effect after isoload vs isokinetic eccentric supra-maximal single session.Methods: Thirty sport science male students were randomly divided in isokinetic (IK) and isoload (IL) eccentric training. Creatin kinase (CK) serum activity, muscle soreness and strength decrement measured both in dynamic and isometric modalities were recorded at baseline, immediately after and up to 4 days following 48 supramaximal IK or IL eccentric contractions. Same protocol was repeated after 4 weeks. A three-way repeated measures ANOVA was used to detect differences in dependent variables comparing group × bout × time.Results: No three-way interaction occurred in dependent variables. Bout × time resulted in a significant interaction in all dependent variables. Muscle damage markers resulted significantly altered compared to baseline up to 4 days. However, IL showed significantly greater CK, muscle soreness and strength deficit compared to IK. All parameters were significantly reduced after second compared to first bout. Difference between IL and IK after second bout was not overall significant.Conclusion: IK vs IL supra-maximal eccentric contraction is showed to have different muscle damage symptoms. Protection conferred by first bout reduced muscle damage after 4 weeks and decreased difference between IL and IK.