Downloaded from https://journals.lww.com/acsm-msse by BhDMf5ePHKav1zEoum1tQfN4a+kJLhEZgbsIHo4XMi0hCywCX1AWnYQp/IlQrHD3n4/ufkX3x2fK8k/+r9PIrO/yD7BhCoQkAFpcwqR6c08= on 03/16/2018 Downloaded from https://journals.lww.com/acsm-msse by BhDMf5ePHKav1zEoum1tQfN4a+kJLhEZgbsIHo4XMi0hCywCX1AWnYQp/IlQrHD3n4/ufkX3x2fK8k/+r9PIrO/yD7BhCoQkAFpcwqR6c08= on 03/16/2018 Muscle Fiber and Performance Changes after Fast Eccentric Complex Training GREGORY C. BOGDANIS 1 , ATHANASIOS TSOUKOS 1 , LEE E. BROWN 2 , ELISAVET SELIMA 1 , PANAGIOTIS VELIGEKAS 1 , KONSTANTINOS SPENGOS 3 , and GERASIMOS TERZIS 1 1 School of P.E. and Sport Science, National and Kapodistrian University of Athens, Athens, GREECE; 2 Human Performance Laboratory, California State University, Fullerton, Fullerton, CA; and 3 Division of Neurology, Eginition Hospital, School of Medicine, National and Kapodistrian University of Athens, Athens, GREECE ABSTRACT BOGDANIS, G. C., A. TSOUKOS, L. E. BROWN, E. SELIMA, P. VELIGEKAS, K. SPENGOS, and G. TERZIS. Muscle Fiber and Performance Changes after Fast Eccentric Complex Training. Med. Sci. Sports Exerc., Vol. 50, No. 4, pp. 729–738, 2018. Introduction: The purpose of this study was to examine the effects of a short-term fast eccentric and ballistic complex training program on muscle power, rate of force development (RFD), muscle fiber composition, and cross-sectional area (CSA). Methods: Sixteen male physical education students were randomly assigned to either a training group (TG, n = 8) or a control group (n = 8). The TG followed a 6-wk low volume training program, including fast eccentric squat training with an individually optimized load of 74% T 7% of maximal half-squat strength (1RM) twice per week and a ballistic training session with loaded (30% 1RM) and unloaded jump squats, once per week, all combined with unloaded plyometric jumps. Results: Half squat 1RM was increased in the TG from 1.87 T 0.28 to 2.14 T 0.31 kg per kilogram body mass (14.4% T 9.3%, P = 0.01). The percentage of types I, IIA, and IIX fibers were similar in the two groups at pretesting and did not change after the intervention period (P = 0.53–0.89). Muscle fiber CSA increased in all fiber types by 8.3% to 11.6% (P = 0.02 to 0.001) in TG only. Countermovement jump height and peak power measured at five different external loads (0%–65% of 1RM) only increased in the TG by approximately 20% to 36% (P G 0.01) and approximately 16% to 22% (P G 0.01), respectively. Peak ground reaction force during jump squats remained unchanged in both groups, whereas RFD increased in the TG only (40%–107%, P = 0.001). Conclusions: A combination of low-volume fast eccentric and ballistic jump squat training with plyometric jumps in a strength–power potentiation complex format, induced substantial increases in peak leg muscle power, RFD, and maximal strength, accompanied by gains in CSA of all muscle fiber types, without a reduction in fast twitch fiber composition. Key Words: RESISTANCE TRAINING, PLYOMETRIC TRAINING, FIBER TYPE, CROSS-SECTIONAL AREA, RATE OF FORCE DEVELOPMENT, JUMP HEIGHT M uscle power is important for success in many sports and thus numerous studies have aimed to determine the characteristics of effective training programs that maximize adaptations in dynamic, multijoint movements (1). A wide range of training loads and methods have been shown to improve muscle power or rate of force development (RFD). These include high load (985% of 1 repetition maximum [1RM]) to low repetition programs with intention to move fast (1,2), heavy-load constant pace re- sistance training (3), lower load (0%–50% of 1RM) ballistic programs (4), plyometric training (5), or a combination of these methods (1). One of the main mechanisms for the enhancement of power is an increase in type II (IIa and IIX) muscle fiber cross-sectional area (CSA) (6,7). However, heavy resistance training protocols typically result in a decrease in the per- centage of type IIX fibers, and thus improve mainly maximal strength rather than muscle power (4,8–10). For example, Andersen and Aagaard (8) have shown that 12 wk of heavy- load resistance training resulted in a decrease in myosin heavy chain (MHC) IIX content from approximately 9% to 2%, whereas MHC IIA content increased from approximately 42% to 49%. In that study, a significant increase in the CSA of type II fibers was observed after training, in parallel with an increase in maximal isometric quadriceps strength. Training with eccentric muscle actions may be used as an effective alternative method to concentric actions to in- duce favorable neuromuscular adaptations, due to the greater maximal force developed (11). Gillies et al. (12) investigated the effects of long-duration (6 s) concentric and eccentric leg exercises on muscle strength and fiber composition and found that the participants increased maximal strength sim- ilarly, with slow eccentric actions inducing an increase in type I fiber proportion and CSA. However, there is evidence to suggest that fast isokinetic eccentric muscle actions may result in greater muscle hypertrophy and strength gains Address for correspondence: Gregory C. Bogdanis, M.Sc., Ph.D., School of Physical Education and Sports Sciences, 41 Ethnikis Antistasis Str, Daphne, 17237, Athens, Greece; E-mail: gbogdanis@phed.uoa.gr. Submitted for publication July 2017. Accepted for publication November 2017. 0195-9131/18/5004-0729/0 MEDICINE & SCIENCE IN SPORTS & EXERCISE Ò Copyright Ó 2017 by the American College of Sports Medicine DOI: 10.1249/MSS.0000000000001507 729 APPLIED SCIENCES Copyright © 2018 by the American College of Sports Medicine. 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