The relationship between joint strength and standing vertical jump performance

The effect of joint strengthening on standing vertical jump height is investigated by computer simulation. The human model consists of five rigid segments representing the feet, shanks, thighs, HT (head and trunk), and arms. Segments are connected by frictionless revolute joints and model movement is driven by joint torque actuators. Each joint torque is the product of maximum isometric torque and three variable functions of instantaneous joint angle, angular velocity, and activation level, respectively. Jumping movements starting from a balanced initial posture and ending at takeoff are simulated. A matching simulation reproducing the actual jumping movement is generated by optimizing joint activation level. Simulations with the goal of maximizing jump height are repeated for varying maximum isometric torque of one joint by up to +/-20% while keeping other joint strength values unchanged. Similar to previous studies, reoptimization of activation after joint strengthening is necessary for increasing jump height. The knee and ankle are the most effective joints in changing jump height (by as much as 2.4%, or 3 cm). For the same amount of percentage increase/decrease in strength, the shoulder is the least effective joint (which changes height by as much as 0.6%), but its influence should not be overlooked.     

Ten minutes of dynamic stretching is sufficient to potentiate vertical jump performance characteristics

The current literature recommends dynamic rather than static stretching for the athletic warm-up. Dynamic stretching and various conditioning stimuli are used to induce potentiation in subsequent athletic performance. However, it is unknown as to which type of activity in conjunction with dynamic stretching within a warm-up provides the optimal potentiation of vertical jump performance. It was the objective of the study to examine the possible potentiating effect of various types of conditioning stimuli with dynamic stretching. Twenty athletes participated in 6 protocols. All the experimental protocols included 10 minutes of dynamic stretching. After the dynamic stretching, the subjects performed a (a) concentric (DS/CON): 3 sets of 3 repetition maximum deadlift exercise; (b) isometric (DS/ISOM): 3 sets of 3-second maximum voluntary contraction back squats; (c) plyometric (DS/PLYO): 3 sets of 3 tuck jumps; (d) eccentric (DS/ECC): 3 modified drop jumps; (e) dynamic stretching only (DS), and (f) control protocol (CON). Before the intervention and at recovery periods of 15 seconds, 4, 8, 12, 16, and 20 minutes, the participants performed 1-2 maximal countermovement jumps. The DS and DS/CON protocols generally had a 95-99% likelihood of exceeding the smallest worthwhile change for vertical jump height, peak power, velocity and force. However, the addition of the deadlift to the DS did not augment the potentiating effect. Time-to-peak potentiation was variable between individuals but was most consistent between 3 and 5 minutes. Thus, the volume and the intensity associated with 10 minutes of dynamic stretching were sufficient to provide the potentiation of vertical jump characteristics. Additional conditioning activities may promote fatigue processes, which do not permit further potentiation.     

The effects of drop vertical jump technique on landing and jumping kinetics and jump performance

The drop vertical jump is a popular plyometric exercise. Two distinct techniques are commonly used to initiate the drop vertical jump. With the ‘step-off’ technique, athletes step off a raised platform with their dominant limb, while their non-dominant limb remains on the platform. In contrast, with the ‘drop-off’ technique, athletes lean forward and drop off the platform, with both feet leaving the platform more simultaneously. The purpose of this study was to compare landing and jumping kinetics, inter-limb kinetic symmetry, and jump performance when individuals used the step-off and drop-off techniques, and to examine whether potential differences between these techniques are affected by platform height. Sixteen subjects completed drop vertical jumps with the drop-off and step-off techniques, from relatively low and high platform heights. Ground reactions forces were recorded for the dominant and non-dominant limbs during the land-and-jump phase of the drop vertical jump. Subjects demonstrated greater inter-limb asymmetry in peak impact forces when using the step-off technique, vs. the drop-off technique. This difference between the techniques was consistent across platform heights. The step-off technique appears to result in greater asymmetry in limb loading, which could contribute to the development of neuromuscular asymmetries between the limbs and/or asymmetric landing patterns.     

Relationship between vertical jump tests and ice skating performance in junior Polish ice hockey players

The aim of this study was to determine the relationships between vertical jumps (VJ) and various on-ice skating performances of junior ice hockey players (n = 19). The three modes of VJ or off-ice measures were countermovement jump with arm swing (CMJ), squat jump (SJ) and depth drop jump (DDJ). The on-ice skating performance was measured by the skating multistage aerobic test (SMAT), forward and backward acceleration test, top speed test, and repeated sprint ability (RSA) test. The relationships between the variables were quantified using Pearson’s product-moment correlation. DDJ showed a significant positive correlation with forward average skating speed (FASS) (r = 0.62) and strong correlations with backward average skating speed (BASS) (r = 0.81), and maximum skating speed (MSS) (r = 0.71). SJ was found to be strongly correlated with BASS (r = 0.82) and MSS (r = 0.76), whereas the only on-ice performance that significantly correlated with CMJ was BASS (r = 0.68). All three modes of VJ were inversely and non-significantly correlated with performance decrement index and fatigue index, as determined by the RSA test. SMAT was not significantly correlated with either VJ or RSA. Correlations between all three modes of VJ tests were significant. Therefore, this study concludes that: (1) DDJ can be used as a predictor of all the ice skating speed tests, whereas SJ can predict BASS and MSS. CMJ, on the other hand, can predict the performance of only BASS. (2) RSA performance cannot be predicted from CMJ, SJ, or DDJ tests, and (3) neither any of the VJ nor RSA can predict skating endurance of junior ice hockey players.     

The effect of short-term VertiMax vs. depth jump training on vertical jump performance

The ability to generate lower body explosive power is considered an important factor in many athletic activities. Thirty-one men and women, recreationally trained volunteers, were randomly assigned to 3 different groups (control, n = 10; VertiMax, n = 11; and depth jump, n = 10). A Vertec measuring device was used to test vertical jump height pre- and post-training. All subjects trained twice weekly for 6 weeks, performing approximately 140 jumps. The VertiMax group increased elastic resistance and decreased volume each week, while the depth jump group increased both box height and volume each week. The depth jump group significantly increased their vertical jump height (pre: 20.5 +/- 3.98; post: 22.65 +/- 4.09), while the VertiMax (pre: 22.18 +/- 4.31; post: 23.36 +/- 4.06) and control groups (pre: 15.65 +/- 4.51; post: 15.85 +/- 4.17) did not change. These findings suggest that, within the volume and intensity constraints of this study, depth jump training twice weekly for 6 weeks is more beneficial than VertiMax jump training for increasing vertical jump height. Strength professionals should focus on depth jump exercises in the short term over commercially available devices to improve vertical jump performance.     

Use of an overhead goal alters vertical jump performance and biomechanics

This study examined whether an extrinsic motivator, such as an overhead goal, during a plyometric jump may alter movement biomechanics. Our purpose was to examine the effects of an overhead goal on vertical jump height and lower-extremity biomechanics during a drop vertical jump and to compare the effects on female (N = 18) versus male (N = 17) athletes. Drop vertical jump was performed both with and without the use of an overhead goal. Greater vertical jump height (p = 0.002) and maximum takeoff external knee flexion (quadriceps) moment (p = 0.04) were attained with the overhead goal condition versus no overhead goal. Men had significantly greater vertical jump height (p < 0.001), maximum takeoff vertical force (p = 0.009), and maximum takeoff hip extensor moment (p = 0.02) compared with women. A significant gender x overhead goal interaction was found for stance time (p = 0.02) and maximum ankle (p = 0.04) and knee flexion angles (p = 0.04), with shorter stance times and lower angles in men during overhead goal time. These results indicate that overhead goals may be incorporated during training and testing protocols to alter lower-extremity biomechanics and can increase performance.     

Acute effects of heavy preloading on vertical and horizontal jump performance

The purpose of this study was to investigate the acute effects of a heavy dynamic preload, consisting of 1 set of 5 repetition maximum (5RM) back squats, on countermovement vertical jump (VJ) and horizontal jump (HJ) performance. The study also investigated the ability of subjects to learn to apply the effects of the preload over subsequent training sessions. Nineteen (N = 19) resistance-trained men (age = 25.0 +/- 4.8 years; weight = 79.3 +/- 6.6 kg) participated in the study. Each subject took part in 4 practice and 4 testing sessions. The 4 practice sessions were included to allow for any learning effects of VJ and HJ to stabilize and to establish a true 5RM back squat. The 4 testing sessions were included to see if subjects were able to capitalize on the repeat exposure to the protocol. One practice session consisted of a 10-minute warm-up (5 minutes of cycling and 5 minutes of stretching), 2 sets of VJ and HJ (each set of VJ and HJ consisted of 4 jump repetitions) with a 5-minute rest between sets, progressive 5RM back squat evaluation, and 2 final sets of VJ and HJ. Both VJ and HJ increased approximately 2% over the 4 practice sessions, and 5RM back squat strength improved from 164.2 +/- 25.1 kg to 196.9 +/- 23.0 kg (p < or = 0.05). The 4 testing sessions each consisted of the standardized warm-up, 1 set of 4 VJs and HJs, a 5-minute rest, 5RM back squat, a 5-minute rest, and the final set of VJs and HJs. Pre- and post-5RM VJ and HJ order was randomly assigned. The results indicated no significant differences occurred between the mean or maximal values for either VJ or HJ as a consequence of the dynamic preload exercise. In addition, the results reflected an inability of subjects to benefit from the repeated exposure to the heavy dynamic preload exercise protocol.     

Comparison of land- and aquatic-based plyometric training on vertical jump performance

Plyometric training is a popular method by which athletes may increase power and explosiveness. However, plyometric training is considered a highly intense and potentially damaging activity particularly if practiced by the novice individual or if overdone. The purpose of this study was to compare vertical jump performance after land- and aquatic-based plyometric training. A convenience sample of 21 active, college-age (24 +/- 2.5 years) men were randomly assigned to 1 of 3 groups: group I, aquatic; group II, land; and group III, control. Training for the AQ and LN groups consisted of a 10-minute warm-up followed by 3 sets of 15 squat jumps, side hops, and knee-tuck jumps separated by 1-minute rests. The aquatic group performed the exercises in knee-level water adjusted to parallel the axis of the knee joint (+1 in.). The land group performed identical plyometric exercises on land. The control group engaged in no training. Participants trained twice a week for 6 weeks, and all training sessions were monitored. Pre- and post-test data were collected on maximum vertical jump height. A 2x3 analysis of variance with repeated measures was used to compare vertical jump height among the 3 groups. Results suggested that the aquatic- and land-based groups significantly (p < 0.05) outperformed the control group in the vertical jump. No significant difference was found in vertical jump performance between the aquatic- and land-based groups. It was concluded that aquatic training resulted in similar training effects as land-based training, with a possible reduction in stress due to the reduction of impact afforded by the buoyancy and resistance of the water upon landing.     

Understanding how an arm swing enhances performance in the vertical jump

This investigation was conducted to examine the various theories that have been proposed to explain the enhancement of jumping performance when using an arm swing compared to when no arm swing is used. Twenty adult males were asked to perform a series of maximal vertical jumps while using an arm swing and again while holding their arms by their sides. Force, motion and electromyographical data were recorded during each performance. Participants jumped higher (0.086 m) in the arm swing compared to the no-arm swing condition and was due to increased height (28%) and velocity (72%) of the center of mass at take-off. The increased height at take-off was due to the elevation of the arm segments. The increased velocity of take-off stemmed from a complex series of events which allowed the arms to build up energy early in the jump and transfer it to the rest of the body during the later stages of the jump. This energy came from the shoulder and elbow joints as well as from extra work done at the hip. This energy was used to (i) increase the kinetic and potential energy of the arms at take-off, (ii) store and release energy from the muscles and tendons around the ankle, knee and hip joint, and (iii) ‘pull’ on the body through an upward force acting on the trunk at the shoulder. It was concluded that none of the prevailing theories exclusively explains the enhanced performance in the arm swing jump, but rather the enhanced performance is based on several mechanisms operating together.     

Association of drop vertical jump displacement with select performance variables

Drop vertical jumps (DVJs) stimulate enhanced countermovement loading as would occur with a run-up before jumping. A variety of performance variables have been associated with DVJ performance including ground contact time (GCT), reactive strength index (RSI), eccentric utilization ratio (EUR), and elasticity index (EI). This study examined the stability reliability and precision of these variables and their associations with DVJ displacement in trained men and women. The EUR and EI measures were redundant, so only EUR findings were reported. Except for EUR, data for all variables were both reliable and precise (intraclass correlation coefficient ≥ 0.70, coefficient of variation [CV%] ≤ 15.0) although EUR data were precise (CV% ≤ 15.0). Correlations with DVJ displacement were low for GCT, moderate for RSI, and negligible for EUR. Therefore, GCT and EUR likely represent unique performance characteristics not related to DVJ displacement. Furthermore, the variability in DVJ performance accounted for by RSI may primarily reflect the inclusion of displacement as the numerator in the quotient for calculating it.     

Investigation of vertical jump performance after completing heavy squat exercises

The purpose of this study was to determine whether vertical jump height was influenced by completing a half squat or quarter squat exercise prior to jumping. Ten male subjects experienced with the squat exercise performed 4 warm up squat sets followed by 1 repetition with the weight of 90% of 1 repetition maximum of the half squat or quarter squat. No difference in jump heights after any of the 3 conditions, including a control group (F = 3.096, p = 0.070), was found. Correlations between the relative strength ratio and the difference in averaged jump heights before and after the half and quarter squat conditions were also tested, and no correlation was found (r = -0.128, p = 0.724, and r = -0.189, p = 0.601, respectively). Although statistical significance at the 0.05 level was not observed for the comparison of jump heights between conditions, we did observe a trend (i.e., p = 0.07). Therefore, we examined the individual responses to the exercises and determined that 5 of the subjects did increase their vertical jumps after both squat exercises. It may be that the influence of prejump exercise on jump performance may be individualized. Nevertheless, the use of a strength ratio does not appear to predict who will benefit from posttetanic potentiation in this type of exercise situation.     

Acute effect of whole-body vibration on electromechanical delay and vertical jump performance

Objectives:To determine if a change in vertical jump performance from acute whole-body vibration can be explained by indirectly assessing spindle sensitivity from electromechanical delay.Methods:Using a counter-balanced design, twenty college-aged participants performed whole-body vibration (WBV) and control treatments. WBV included 10 intervals (26 Hz, 3.6 mm) of 60 s in a half-squat followed by 60 s of rest. After 5 intervals, participants rested for 6-minutes before commencing the final 5 intervals. For the control, the exact same protocol of whole-body vibration was performed but without vibration. Electromechanical delay and vertical jump were assessed at baseline, during the 6-minute rest period and immediately after whole-body vibration and control.Results:There were no differences between treatments, for both electromechanical delay (F(2, 38)=1.385, p=0.263) and vertical jump (F(2, 38)=0.040, p<0.96). Whole-body vibration had no effect on vertical jump performance.Conclusion:The current whole-body vibration protocol is not effective for acute vertical jump or electromechanical delay enhancement. Also, since there was no effect on electromechanical delay, this suggests that whole-body vibration did not enhance muscle spindle sensitivity for the parameters examined.     

Effects of plyometric training and recovery on vertical jump performance and anaerobic power

We examined the effects of 2 plyometric training programs, equalized for training volume, followed by a 4-week recovery period of no plyometric training on anaerobic power and vertical jump performance. Physically active, college-aged men were randomly assigned to either a 4-week (n = 19, weight = 73.4 +/- 7.5 kg) or a 7-week (n = 19, weight = 80.1 +/- 12.5 kg) program. Vertical jump height, vertical jump power, and anaerobic power via the Margaria staircase test were measured pretraining (PRE), immediately posttraining (POST), and 4 weeks posttraining (POST-4). Vertical jump height decreased in the 4-week group PRE (67.8 +/- 7.9 cm) to POST (65.4 +/- 7.8 cm). Vertical jump height increased from PRE to POST-4 in 4-week (67.8 +/- 7.9 to 69.7 +/- 7.6 cm) and 7-week (64.6 +/- 6.2 to 67.2 +/- 7.6 cm) training programs. Vertical jump power decreased in the 4-week group from PRE (8,660.0 +/- 546.5 W) to POST (8,541.6 +/- 557.4 W) with no change in the 7-week group. Vertical jump power increased PRE to POST-4 in 4-week (8,660.0 +/- 546.5 W to 8,793.6 +/- 541.4 W) and 7-week (8,702.8 +/- 527.4 W to 8,931.5 +/- 537.6 W) training programs. Anaerobic power improved in the 7-week group from PRE (1,121.9 +/- 174.7 W) to POST (1,192.2 +/- 189.1 W) but not the 4-week group. Anaerobic power significantly improved PRE to POST-4 in both groups. There were no significant differences between the 2 training groups. Four-week and 7-week plyometric programs are equally effective for improving vertical jump height, vertical jump power, and anaerobic power when followed by a 4-week recovery period. However, a 4-week program may not be as effective as a 7-week program if the recovery period is not employed.     

Bilateral and gender differences during single-legged vertical jump performance in healthy teenagers

The determination of physiologic lower limb functional imbalance among healthy teenagers is important to follow the rehabilitation progress and return to normal activity of injured subjects. We investigated the differences in vertical jump capacity between both legs in a group of healthy boys and girls, considering the performances in the dominant vs. non-dominant, and in the most vs. least efficient leg. Strength and power performances were compared in 117 boys and 106 girls aged 10-16 years during a single-leg vertical countermovement jump (SLVCJ) test. When leg dominance was defined subjectively by the participant, no difference was noted between the 2 legs. Statistically significant differences were recorded between the most and less efficient leg in strength and power performances for both genders. Girls had significantly greater peak strength than did age-matched boys, but boys showed significant increases in maximal power outputs compared with that shown by age-matched girls. When the results were analyzed according to the percentage of participants falling within certain bands of limb asymmetry, approximately 20-30% showed a difference of >15% between the 2 limbs without any relation to gender. Subjective expression of leg dominance cannot be used as a predictor of SLVCJ performance. Differences of <15% in SLVCJ performance between both legs should be considered as the physiological norm in this age group. A greater appreciation of the potential diagnostic value of the SLVCJ test may be obtained if the results are interpreted in terms of the percentage of subjects falling within certain bands of limb asymmetry. Gender-based differences in the SLVCJ test vary and depend upon whether the results are interpreted in terms of strength or power output.     

Varying amounts of acute static stretching and its effect on vertical jump performance

Numerous studies have shown that stretching routines can induce strength and force deficits, although the amount of stretching needed to cause these deficits remains unclear. Therefore, the purpose of the study was to examine the relationship between varying amounts of acute static stretching on jumping performance. By systematically increasing the amount of stretching, possible differences in jump height may be discovered, defining a line where acute static stretching becomes detrimental to performance. Ten collegiate athletes and 10 recreational athletes completed 3 different stretching treatments and 1 control treatment on different days in a within-treatment design. Stretching treatments consisted of 2, 4, or 6 sets of stretches, with each stretch held for 15 seconds with a 15-second rest. Stretches were done to the quadriceps, hamstrings, and plantar flexors. Upon arrival, each subject performed a 5-minute warm-up on a stationary upright cycle. After a brief rest period, participants performed 3 trials of a vertical jump test, followed by one of the treatment protocols. After another rest period, a second set of vertical jump trials was performed. Post-6 sets was significantly lower than Pre-6 sets (p < or = 0.05). Additionally, Post-6 sets was significantly lower than Pre-4 sets, Pre-2 sets, and Pre-control (p < or = 0.05). No other conditions were significantly different. In conclusion, 6 sets of stretches, or 90 seconds per muscle group, should not be performed before power activities such as jumping where optimal performance is desired.     

Relations between ameboid movement and membrane-controlled electrical currents

We have studied the pattern of electrical currents through amebas (mainly Chaos chaos) with an ultrasensitive extracellular vibrating probe. Amebas drive both steady currents and current pulses through themselves. Relatively steady current with an average surface density of 0.1-0.2 muA/cm2 enters the rear quarter of an ameba and leaves its pseudopods. Streaming reversals are preceded by changes in this current pattern and the region with the largest new inward current becomes the new tail. Ion substitution studies suggest that some of the steady inward current is carried by calcium ions. Characteristic stimulated pulses of current sometimes follow the close approach of the vibrating probe to the side of an advancing pseudopod. Such a pulse enters the cytoplasm through a small patch of membrane near the probe (and seems to leave through the adjacent membrane), is usually followed by hyaline cap and then by pseudopod initiation, is calcium dependent, lasts about 5-10 s, and has a peak density of about 0.4 muA/cm2. Spontaneous pulses of similar shape and duration may enter or leave any part of an animal. They are much less localized, tend to have higher peak densities, and occur in physiological salt solutions at about 0.2-4 times per minute. Retraction of a pseudopod is always accompanied or preceded by a spontaneous pulse which leaves its sides.     

Effect of different rest intervals after whole-body vibration on vertical jump performance

Whole-body vibration (WBV) may potentiate vertical jump (VJ) performance via augmented muscular strength and motor function. The purpose of this study was to evaluate the effect of different rest intervals after WBV on VJ performance. Thirty recreationally trained subjects (15 men and 15 women) volunteered to participate in 4 testing visits separated by 24 hours. Visit 1 acted as a familiarization visit where subjects were introduced to the VJ and WBV protocols. Visits 2-4 contained 2 randomized conditions per visit with a 10-minute rest period between conditions. The WBV was administered on a pivotal platform with a frequency of 30 Hz and an amplitude of 6.5 mm in 4 bouts of 30 seconds for a total of 2 minutes with 30 seconds of rest between bouts. During WBV, subjects performed a quarter squat every 5 seconds, simulating a countermovement jump (CMJ). Whole-body vibration was followed by 3 CMJs with 5 different rest intervals: immediate, 30 seconds, 1 minute, 2 minutes, or 4 minutes. For a control condition, subjects performed squats with no WBV. There were no significant (p > 0.05) differences in peak velocity or relative ground reaction force after WBV rest intervals. However, results of VJ height revealed that maximum values, regardless of rest interval (56.93 ± 13.98 cm), were significantly (p < 0.05) greater than the control condition (54.44 ± 13.74 cm). Therefore, subjects' VJ height potentiated at different times after WBV suggesting strong individual differences in optimal rest interval. Coaches may use WBV to enhance acute VJ performance but should first identify each individual's optimal rest time to maximize the potentiating effects.     

Kinetic analysis of complex training rest interval effect on vertical jump performance

Complex training has been recommended as a method of incorporating plyometrics with strength training. Some research suggests that plyometric performance is enhanced when performed 3-4 minutes after the strength training set, whereas other studies have failed to find any complex training advantage when plyometrics are performed immediately after the strength training portion of the complex. The purpose of this study was to determine if there is an ergogenic advantage associated with complex training and if there is an optimal time for performing plyometrics after the strength training set. Subjects were 21 NCAA Division I athletes who performed a countermovement vertical jump, a set of 5 repetitions maximum (5 RM) squats, and 5 trials of countermovement vertical jump at intervals of 10 seconds and 1, 2, 3, and 4 minutes after the squat. Jump height and peak ground reaction forces were acquired via a force platform. The pre-squat jump performance was compared with the post-squat jumps. Repeated measures ANOVA determined a difference (p 0.05) was found comparing subsequent jumps (0.72-0.76 m) to the pre-squat condition (0.74 m). When comparing high to low strength individuals, there was no effect on jump performance following the squat (p > 0.05). In conclusion, complex training does not appear to enhance jumping performance significantly and actually decreases it when the jump is performed immediately following the strength training set; however, a nonsignificant trend toward improvement seemed to be present. Therefore to optimize jump performance it appears that athletes should not perform jumps immediately following resistance training. It may be possible that beyond 4 minutes of recovery performance could be enhanced; however, that was not within the scope of the current study.     

The effects of proprioceptive neuromuscular facilitation and dynamic stretching techniques on vertical jump performance

The purpose of this study was to investigate the effects of 3 different warm-ups on vertical jump performance. The warm-ups included a 600-m jog, a 600-m jog followed by a dynamic stretching routine, and a 600-m jog followed by a proprioceptive neuromuscular facilitation (PNF) routine. A second purpose was to determine whether the effects of the warm-ups on vertical jump performance varied by gender. Sixty-eight men and women NCAA Division I athletes from North Dakota State University performed 3 vertical jumps on a Just Jump pad after each of the 3 warm-up routines. The subjects were split into 6 groups and rotated between 3 warm-up routines, completing 1 routine each day in a random order. The results of the 1-way repeated measures analysis of variance showed no significant differences in the combined (p = 0.927), men's (p = 0.798), or women's (p = 0.978) results. The results of this study showed that 3 different warm-ups did not have a significant affect on vertical jumping. The results also showed there were no gender differences between the 3 different warm-ups.     

Short-term effects of selected exercise and load in contrast training on vertical jump performance

The present study examined the short-term effects of loaded half squats (HSs) and loaded jump squats (JSs) with low and moderate loads on the squat jump (SJ) and the countermovement jump (CMJ) performance using a contrast training approach. Ten men (mean +/- SD age, 23 +/- 1.8 years) performed the HS and JS exercises twice with loads of 30% of 1 repetition maximum (1RM) (HS30% and JS30%, respectively) and 60% of 1RM (HS60% and JS60%, respectively). On each occasion, 3 sets of 5 repetitions with 3 minutes of rest were performed as fast as possible. Vertical jump performance was measured before exercise, 1 minute after each set, and at the fifth and 10th minutes of recovery. The CMJ increased significantly after the first and second set (3.9%; p < 0.05) compared with preexercise values following the JS30% protocol and 3.3% after the second and third sets of the JS60% protocol. Following the HS60% protocol, CMJ increased after the first and the second sets (3.6%; p < 0.05) compared with preexercise values, whereas SQ increased only after the first set (4.9%; p < 0.05) in this condition. These data show that contrast loading with the use of low and moderate loads can cause a short-term increase in CMJ performance. The applied loads do not seem to present different short-term effects after loaded JSs. When the classic form of dynamic HS exercise is performed, however, at least a moderate load (60% of 1RM) needs to be applied.