THE EFFECTS OF ECCENTRIC CONDITIONING STIMULI ON SUBSEQUENT COUNTER-MOVEMENT JUMP PERFORMANCE JOO HAW ONG, 1,2 JULIAN LIM, 2 EDWIN CHONG, 2 AND FRANKIE TAN 2,3 1 Sports Medicine Centre, Khoo Teck Puat Hospital, Singapore; 2 Sports Science Centre, Singapore Sports Institute, Sport Singapore, Singapore; and 3 Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore ABSTRACT Ong, JH, Lim, J, Chong, E, and Tan, F. The effects of eccentric conditioning stimuli on subsequent counter-movement jump performance. J Strength Cond Res 30(3): 747–754, 2016—The eccentric phase in a stretch-shortening cycle is an important deter- minant of subsequent concentric performance, but there is little information on high-intensity eccentric preconditioning. The pur- pose of this study was to determine the effects of varying degrees of eccentric conditioning stimuli on subsequent counter-movement jump (CMJ) performance. Fourteen participants (age, 28.5 6 5.0 years; height, 172.7 6 6.7 cm; body mass, 74.3 6 11.9 kg) performed CMJ trials on 3 separate test sessions at least 96 hours apart in a crossover randomized counterbalanced study. Peak power (P peak ) and vertical displacement (D max ) were measured before and at 3, 6, 9, and 12 minutes (T3–12) postcontrol (0RM), 105% (105RM), and 125% (125RM) 1RM eccentric hip sled. The differences in vertical jump performance parameters between 0RM and eccentric preloading conditions (105RM and 125RM) and the differences within condition between control time point and posteccentric load time course T3, T6, T9, and T12 were analyzed for statistical significance via unequal variance t statistic. Statistical significance was set at p # 0.05. Significantly higher P peak , compared with 0RM (4143 6 754 W) was seen at T3 and T6 in both 105RM (4305 6 876 and 4237 6 842 W) and 125RM (4314 6 848 and 4264 6 768 W). Compared with 0RM (42.2 6 7.8 cm), corresponding D max , was also significantly improved at T3 in both 105RM (44.5 6 7.3 cm) and 125RM (44.3 6 8.3 cm) and at T6 in 105RM (44.7 6 7.7 cm). Compared with baseline (43.2 6 7.2 cm), there was significantly higher D max at T3 and T6 in 105RM. In conclusion, high-intensity precondition- ing eccentric contraction at 105 and 125% 1RM was effective in improving CMJ power and height at 3 and 6 minutes after loading. Thus, power athletes and coaches can consider the application of eccentric preconditioning in warm-up routines. KEY WORDS postactivation potentiation, complex training, plyometrics, stretch-shortening cycle, warm-up INTRODUCTION I n most human activities, concentric movement toward the intended direction is preceded by an eccentric movement in the opposite direction. The eccentric– concentric coupling is termed a stretch-shortening cycle (SSC). In a vertical jump, the SSC of the lower limb muscula- ture contributes to greater jump heights when compared with non-SSC jumps (27). Therefore, plyometric activities involving the SSC use varying intensities of counter-movement jumps (CMJ), ranging from simple jumps in place to the accentuated eccentric loading (AEL) of drop jumps (1), to train athletes. Complex training is a method that combines high-load conditioning exercise that stimulates the neuromuscular system, followed by a plyometric exercise involving the same muscle groups in which power output is augmented (11). This enhance- ment of performance is termed postactivation potentiation (PAP), which is defined as a phenomenon in which muscular performance is enhanced acutely after an activity executed at relatively high intensity (28). Lowery et al. (28) showed, in a vol- ume-controlled PAP study, that moderate-to-high intensity loading at 70 and 93% concentric one repetition maximum (1RM) through the entire eccentric–concentric squat cycle leads to better jump performance; effects of which peaked at 4 minutes and returned to baseline by 8 minutes. Other studies also dem- onstrated positive effects of PAP on lower limb kinematics and kinetics in jumping (26) and sprinting (29). Previous studies also focused mainly on dynamic (eccentric–concentric) and isomet- ric loading; thus, stimulus was limited to below 1RM, even for activities such as CMJs in which the eccentric component is important (6,25). Eccentric contractions have long been known from early studies to produce greater amounts of torque and force compared with concentric and isometric contractions. In a study comparing upper body concentric, eccentric, and isometric Address correspondence to Joo Haw Ong, ong.joo.haw@ alexandrahealth.com.sg. 30(3)/747–754 Journal of Strength and Conditioning Research Ó 2015 National Strength and Conditioning Association VOLUME 30 | NUMBER 3 | MARCH 2016 | 747 Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.