- Males JUMP HEIGHT significantly higher than females + 26.4%
- LOAD was significantly higher in males + 36.3%
- EXPLODE was significantly higher in males + 5.75%
- TIME and ECC-TIME were not significantly different between males and females
- JUMP HEIGHT: Baseball > football > volleyball and basketball
- LOAD is positively correlated with JUMP HEIGHT r = 0.52
- EXPLODE is positively correlated with JUMP HEIGHT r = 0.57
- Volleyball players have higher TIME and ECC-TIME
- Football and Baseball players have lower TIME and ECC-TIME
- Football and Baseball players have higher LOAD and EXPLODE
- Basketball players have lower LOAD and EXPLODE but also lower TIME and ECC TIME
SUMMARYThe questions covered
- Do sport-specific “signatures” or profiles exist with regard to the inherent demands of their sport?
- What factors of the force time curve result in differences in jump height between males and females?
ABSTRACTLaffaye, G, Wagner, PP, and Tombleson, TIL. Countermovement jump height: Gender and sport-specific differences in the force- time variables. J Strength Cond Res 28(4): 1096–1105, 2014 — The goal of this study was to assess (a) the eccentric rate of force development, the concentric force, and selected time variables on vertical performance during countermovement jump, (b) the existence of gender differences in these variables, and (c) the sport- specific differences. The sample was composed of 189 males and 84 females, all elite athletes involved in college and professional sports (primarily football, basketball, baseball, and volleyball). The subjects performed a series of 6 countermovement jumps on a force plate (500 Hz). Average eccentric rate of force development (ECC-RFD), total time (TIME), eccentric time (ECC-T), Ratio between eccentric and total time (ECC-T:T) and average force (CON-F) were extracted from force-time curves and the vertical jumping performance, measured by impulse momentum. Results show that CON-F (r = 0.57; p , 0.001) and ECC- RFD (r = 0.52, p , 0.001) are strongly correlated with the jump height (JH), whereas the time variables are slightly and negatively correlated (r = 20.21–0.23, p , 0.01). Force variables differ between both sexes (p , 0.01), whereas time variables did not differ, showing a similar temporal structure. The best way to jump high is to increase CON-F and ECC-RFD thus minimizing the ECC-T. Principal component analysis (PCA) accounted for 76.8% of the JH variance and revealed that JH is predicted by a temporal and a force component. Furthermore, the PCA comparison made among athletes revealed sport-specific signatures: volleyball players revealed a temporal-prevailing profile, a weak- force with large ECC-T:T for basketball players and explosive and powerful profiles for football and baseball players.
Countermovement jump height: Gender and sport-specific differences in the force- time variablesLaffaye, G, Wagner, PP, and Tombleson, TIL. Countermovement jump height: Gender and sport-specific differences in the force- time variables. J Strength Cond Res 28(4): 1096–1105, 2014. Introduction Critical information can be directly extracted from the force-time (F-T) curve during the vertical countermovement jump (CMJ), such as time variables, force variables, and variables linking both components (rate of force development, impulse, and power). This information allows trainers and scientists to understand how a subject jumps, specifically the different phases of the movement (eccentric vs. concentric). Moreover, several studies have shown that the shape of the F-T curve is dependent on expertise (9,11,12). This means that with training, neuromuscular properties of the athlete change (10) by increasing the level of force with a higher preload during the eccentric phase, by allowing high interaction between contractile and elastic elements, and by storing and using elastic energy and activating the stretch reflex (6,8,11,15). Considering that the performance during CMJ is the result of the high level of efficiency of all these mechanisms, it is expected that the vertical performance is strongly linked to the mechanical variables responsible for the force production in the concentric and eccentric phases, and in turn, the contribution of the elastic elements and nervous system properties. More specifically, rate of force development (RFD) seems to play a crucial role in activities involving plyometric muscular contractions, such as sprinting or jumping (14,19,25,33,35,36,45). Rate of force development could be defined as the rate of rise of contractile force at the beginning of muscle action (39). Rate of force development has been frequently studied as a force-time variable (1,5,14,19,25,33,35,36,45) often during the concentric phase when the peak occurs, but very rarely during the eccentric phase (11,23) and even less so when taken as an average. This variable has been demonstrated as a crucial variable (6,8,11,15) in the ability to enhance the stretch-shortening cycle (SSC). Analysis of force-time curves reveal gender-specific differences in jump heights (JHs). Various studies show that men tend to jump higher than women (approximately 10 cm) throughout a range of different jump methods (CMJ and Drop Jump) (2,22,32,43,44). This is primarily explained by higher value of relative power, force (2,17,32), and the difference in the eccentric time (28). But only 3 studies have investigated the gender difference in RFD (5,14,24) and only during a plyometric activity, i.e., the CMJ (14). The latter study did not find any RFD difference between men and women, meaning curiously no difference in the efficiency of the prestretching phase of jump. Finally, few studies have investigated sport-specific differences with regard to force-time variables (27,31). These studies demonstrate the role of sport and practice in shaping jumping components. Athletes seem to use jumping strategies, which reveal the specific constraints of their sport. An explosive and force-prevailing profile has been noticed for high jumpers, a time-prevailing profile for volleyball players (31) and a heterogeneous and neutral component for handball and basketball players (27,31). For the best of our knowledge, the force-time signature of football and baseball players has never been investigated. Therefore, based on this theoretical background, the goal of the present study is to (a) assess the contribution of ECCRFD, the CON-F, and the selected time variables on the vertical performance during CMJ, (b) assess the gender differences in these variables, (c) explain the link between these variables, and (d) investigate whether sport-specific “signatures” or profiles exist with regard to the inherent demands of their sport. Methods Experimental Approach to the Problem: The subjects arrived for testing in groups of 2–5 people at a time, on commencement of their training term at the facility. The testing sessions were initiated with a thorough description of the testing procedure before the actual assessment. This was immediately followed by a standardized 10-minute warm-up consisting of self-myofacial release and a number of total body dynamic stretches. After the warmup, subjects were then adequately familiarized with the jump testing with 2 submaximal practice jumps before testing. The testing procedure itself consisted of each subject performing a series of 6 jumps with 30 seconds rest in-between. The subjects were instructed to jump as high as they could by performing a CMJ with an arm swing. No instruction was given on the technique to be used during the CMJ, considering the fact that in skilled jumpers, subjects chose the depth that maximized both peak force and peak velocity resulting in maximal power output (26). Analysis of variance (ANOVA) and correlation coefficients were used to analyze the force-time variables from the force plate. Average eccentric rate of force development (ECC-RFD), total time (TIME), eccentric time (ECC-T), ratio between eccentric time and total time (ECC-T:T), and average vertical concentric force (CON-F) were extracted from the force-time curve and the vertical performance. Vertical JH was calculated from impulse momentum (18,34). Subjects: A total of 273 subjects, including 189 males and 84 females, were used in the study with all major physical characteristics summarized in Table 1. All of the participants were of an T1 elite standard, competing at a college or professional level in a range of sports, including volleyball, basketball, baseball, football, or others. Due to the samples sporting level, all subjects were experienced strength and power athletes, performing training of this nature at least 2 times per week as a part of their typical training regime. Each volunteer signed a written informed consent statement before the investigation after receiving oral and written description of the procedures in accordance with guidelines established by the University Human Subject Review Board. They were informed of the risks and benefits of participation in this study. Moreover, the procedure of this study was approved by the research ethics committee of the University Paris-Sud. Procedures:
- Vertical Jump – All testing was performed with the subject standing on a 0.6 3 0.4-m Bertec 4060-08 piezoelectric force sensor platform (Bertec Corporation, Columbus, OH) with a sampling frequency of 500 Hz. A 20-minute warm-up was performed that consists of standardized 30-second blocks within 10 minutes of myofascial release and 10 minutes of muscle activation and stretching and a familiarization session of CMJ. Then, each subject started the CMJ in the standing position, dropped into the squat position, and then immediately jumped as high as possible. The depth of knee flexion and the amount of arm movement used during each CMJ was individually determined by each subject, considering the fact that in skilled jumpers, subjects chose the depth that maximized both peak force and peak velocity resulting in maximal power output (26). A Vertec measurement device (Sports Imports, Columbus, OH) was used as an overhead goal for the athlete to ensure motivation by giving feedback to the athletes and maximize trajectory in the vertical plane. The JH was calculated from impulse momentum (18,34).
- Force-Time Variables – The independent variables were extracted from the force-time curve and included ECCRFD, R-ECC-RFD, ECC-T, TIME, ECC-T:T, and CON-F. The ECC-RFD (Newtons per second) was determined during the eccentric phase (Figure F1 1). This measurement is based on the average slope of the eccentric loading portion of the force/time curve; it begins AU5 when force exceeds body weight, ends when velocity comes to zero (bottom of descent when loading for jump). This variable has been calculated as an absolute value (ECC-RFD) and as a normalized value of relative eccentric RFD (R-ECC-RFD) by dividing the value of ECC-RFD by body mass to study the independent mass effect. TIME is the total time of the CMJ and ECC-T the eccentric time. ECC-T:T was calculated as the ratio of ECC-T to TIME. The CON-F in Newton per kilograms was calculated during the propulsive phase of the movement and normalized to body mass. The eccentric phase (ECC) starts when movement begins and ends when athlete is at bottom of loading phase of their jump. The propulsive (concentric) phase (CON) starts when the displacement reached its lowest value until the force-time curve returned to zero (Figure 1). The dependent variable was the vertical JH, expressed in centimeters.