Eight weeks of ballistic exercise improves power independently of changes in strength and muscle fiber type expression

This study investigated the effects of ballistic resistance training and strength training on muscle fiber composition, peak force (PF), maximal strength, and peak power (PP). Fourteen males (age = 21.3 [+ or -] 2.9, body mass = 77.8 [+ or -] 10.1 kg) with 3 months of resistance training experience completed the study. Subjects were tested pre and post for their squat one-repetition maximum (1RM) and PP in the jump squat (JS). Peak force and rate of force development (RFD) were tested during an isometric midthigh pull. Muscle biopsies were obtained from the vastus lateralis for analysis of muscle fiber type expression. Subjects were matched for strength and then randomly selected into either training (T) or control (C) groups. Group T performed 8 weeks of JS training using a periodized program with loading between 26 and 48% of 1RM, 3 days per week. Group T showed significant improvement in PP from 4088.9 [+ or -] 520.6 to 5737.6 [+ or -] 651.8 W. Rate of force development improved significantly in group T from 12687.5 [+ or -] 4644.0 to 25343.8 [+ or -] 12614.4 N x [s.sup.-1]. PV improved significantly from 1.59 [+ or -] 0.41 to 2.11 [+ or -] 0.75 m x [s.sup.-1]. No changes occurred in PF, 1RM, or muscle fiber type expression for group T. No changes occurred in any variables in group C. The results of this study indicate that using ballistic resistance exercise is an effective method for increasing PP and RFD independently of changes in maximum strength (1RM, PF), and those increases are a result of factors other than changes in muscle fiber type expression. KEY WORDS training, resistance, isometric, jumping, force