Stretch-shortening Cycle Movements Research Articles

A narrative review of velocity-based training best practice: The importance of contraction intent vs. movement speed.

Explosive movements requiring high force and power outputs are integral to many sports, posing distinct challenges for the neuromuscular system. Traditional resistance training can improve muscle strength, power, endurance, and range of motion; however, evidence regarding its effects on athletic performance, such as sprint speed, agility, and jump height, remains conflicting. The specificity of resistance training movements, including velocity, contraction type, and joint angles affects performance outcomes, demonstrates advantages when matching training modalities with targeted sports activities. However, independent of movement speed, the intent to contract explosively (ballistic) has also demonstrated high velocity-specific training adaptations. The purpose of this narrative review was to assess the impact of explosive or ballistic contraction intent on velocity-specific training adaptations. Such movement intent may predominantly elicit motor efferent neural adaptations, including motor unit recruitment and rate coding enhancements. Plyometrics, which utilize rapid stretch-shortening cycle (SSC) movements may augment high-speed movement efficiency and muscle activation, possibly leading to improved motor control through adaptations like faster eccentric force absorption, reduced amortization periods, and quicker transitions to explosive concentric contractions. An optimal training paradigm for power and performance enhancement might involve a combination of maximal explosive intent training with heavier loads and plyometric exercises with lighter loads at high velocities. This narrative review synthesizes key literature to answer whether contraction intent or movement speed is more critical for athletic performance enhancement, ultimately advocating for an integrative approach to resistance training tailored for sports-specific explosive action.

Increased force and elastic energy storage are not the mechanisms that improve jump performance with accentuated eccentric loading during a constrained vertical jump.

Accentuated eccentric loading (AEL) involves higher load applied during the eccentric phase of a stretch-shortening cycle movement, followed by a sudden removal of load before the concentric phase. Previous studies suggest that AEL enhances human countermovement jump performance, however the mechanism is not fully understood. Here we explore whether isolating additional load during the countermovement is sufficient to increase ground reaction force, and hence elastic energy stored, at the start of the upward movement and whether this leads to increased jump height or power generation. We conducted a trunk-constrained vertical jump test on a custom-built device to isolate the effect of additional load while controlling for effects of squat depth, arm swing, and coordination. Twelve healthy, recreationally active adults (7 males, 5 females) performed maximal jumps without AEL, followed by randomised AEL conditions prescribed as a percentage of body mass (10%, 20%, and 30%), before repeating jumps without AEL. No significant changes in vertical ground reaction force at the turning point were observed. High load AEL conditions (20% and 30% body weight) led to slight reductions in jump height, primarily due to decreased hip joint and centre of mass work. AEL conditions did not alter peak or integrated activation levels of the knee extensor muscles. The constrained movement task used here, which excluded potential contributions of trunk motion, arm swing, rate of descent, squat depth, and point of load application, allows the conclusion that increased elastic energy return is not the primary mechanism for potentiating effects of AEL on jump performance.

Effects of progressive weight addition using vests on rebound jump.

Rebound jump (RJ) is an exercise that is as short contact time and high as possible and is used to improve lower limb stretch-shortening cycle movements. This study examined the effects of RJ performance and lower limb joint kinetics when weight was incrementally added using a weighted vest. Eleven male athletes (mean±standard deviation: age, 21.9±1.6 years; height, 176.3±5.5 cm; weight, 67.8±4.2 kg) performed RJ at 0% (no load), 5%, 9%, 12%, 15%, 18%, and 21% added weight. Body coordinates and ground reaction force were measured, and RJ index (jump height / contact time) and joint kinetics (joint torque, power, and work) were calculated. One-way Analysis of Variance showed that the RJ was significantly reduced starting from 12% (P<0.01), the jump height was significantly decreased starting from 12% (P<0.01), and the contact time was significantly increased only at 21% (P<0.01) compared with 0%. The negative peak power of the ankle joint decreased by 21% of the added weight (P<0.01). The main effects of body weight on the peak torque at the knee and hip joints and the positive peak power at the knee joint were observed. RJ with increasing weight tended to decrease jump height first, rather than longer contact time. However, it was suggested that there is an appropriate range of added weights that can be trained without decreasing the RJ index.

Effects of Flywheel Resistance Training on Muscle Function and Sport-Specific Performance in Collegiate Club Water Polo Players

ABSTRACT Purpose: This study investigated the effects of flywheel squat training on lower body muscle function adaptations and sport-specific performance in collegiate club water polo players. Methods: Thirteen collegiate club water polo athletes (5 women, 8 men) performed flywheel squat training for 4 weeks. Isokinetic knee extension (KE) peak power (PP) and peak torque (PT), flywheel squat peak power (FPP) and mean power (FMP), countermovement jump (CMJ), in-water jump height (WJH) and foot speed were assessed at baseline (Pre1), 4 weeks (Pre2), and 8 weeks (Post) with the first 4 week block being a control period and the second 4 week block being the experimental training. Throughout the training period muscle soreness was assessed using a VAS scale, and FPP and FMP were assessed during every other session. Results: Isokinetic KE PP and PT increased from Pre1 to Post, and FPP and FMP increased between Pre1 and Post, and Pre2 and Post. CMJ and foot speed were unchanged. WJH displayed a change between Pre1 and Post. FPP increased 19% from session 2 to 4 and FMP increased 27% from session 2 to 6, and each remained elevated through session 8. Conclusion: 4 weeks of flywheel squat training in collegiate club water polo players elicited large gains (47–52%) in flywheel-specific squat power, but did not influence sport-specific performance measures including CMJ, WJH, and foot speed. Water-based exercises and stretch-shortening cycle movements (plyometrics) in combination with effective resistance training programs, which may include flywheel-based training, are likely needed for marked sport skill improvements.

Muscle in Variable Gravity: "I Do Not Know Where I Am, But I Know What to Do".

Purpose: Fascicle and sarcomere lengths are important predictors of muscle mechanical performance. However, their regulation during stretch-shortening cycle (SSC) activities in usual and challenging conditions is poorly understood. In this study, we aimed to investigate muscle fascicle and sarcomere behavior during drop jumps (a common SSC activity) in conditions of variable gravity.Methods: Fifteen volunteers performed repeated drop jumps in 1 g, hypo-gravity (0 to 1 g), and hyper-gravity (1 to 2 g) during a parabolic flight. Gastrocnemius medialis (GM) electromyographic activity and fascicle length (Lf) were measured at drop-off, ground contact (GC), minimum ankle joint angle (MAJ), and push-off. GM sarcomere number was estimated by dividing Lf, measured by ultrasound at rest, by published data on GM sarcomere length, and measured in vivo at the same joint angle. Changes in sarcomere length were estimated by dividing GM Lf in each jump phase by sarcomere number calculated individually. The sarcomere force-generating capacity in each jump phase was estimated from the sarcomere length-tension relationship previously reported in the literature.Results: The results showed that, regardless of the gravity level, GM sarcomeres operated in the ascending portion of their length-tension relationship in all the jump phases. Interestingly, although in hypo-gravity and hyper-gravity during the braking phase (GC-MAJ) GM fascicles and sarcomeres experienced a stretch (as opposed to the quasi-isometric behavior in 1 g), at MAJ they reached similar lengths as in 1 g, allowing sarcomeres to develop about the 70% of their maximum force.Conclusion: The observed fascicle behavior during drop jumping seems useful for anchoring the tendon, enabling storage of elastic energy and its release in the subsequent push-off phase for effectively re-bouncing in all gravity levels, suggesting that an innate neuromuscular wisdom enables to perform SSC movements also in challenging conditions.

Effectiveness of Countermovement Jump and Drop Jump on Leg Muscle Power in Young College Athletes: A Comparative Study

Background and Purpose: Plyometric [PT] refers to performance of stretch-shortening cycle (SSC) movements that involve a high intensity eccentric contraction immediately after a rapid and powerful concentric contraction. PT have consistently been shown to improve the production of muscle force and power and enhancement of performance. Plyometric training includes in various type of jumps like Drop jump (DJ), countermovement jumps (CMJ), squat jump, alternate-leg bounding especially for lower body. Drop jump and countermovement jump are simple, practical and effective plyometric exercises. When done with proper technique and effort, both results in an increase in lower body power. So, it is important to know which exercises produce the greatest power output or what technique have must be used to induce changes in specific sport actions. Objectives: The purpose of this study was to compare the effectiveness of countermovement jump and drop jump to improve leg muscle power. Method: 30 subjects volunteered to participate. Written informed consent and institutional ethical clearance was obtained. Anthropometric measurements were obtained and subjects were assigned to one of two groups: Group A: DJ training group (n=15) and Group B: CMJ training group (n=15). They performed either DJ or CMJ training three days a week for 6 weeks. The training program included four sets of 5 repetitions DJ (from the height of a 12-inch box) or CMJ exercise. Standing Long Jump Test (SLJT) was used as outcome measure which was performed a day before and following the 6-week training period. Results: Both the groups showed improvement in standing long jump test. The mean±SD of preand post standing jump test of Group A was 68.63±16.64 and 77.80±14.19 respectively and Group B was 65.83±14.61 and 72.43±13.70 respectively. But the mean±SD difference between the group A and group B was 77.80±14.19 and 72.43±13.70 respectively. Conclusion: The results showed there is significant improvement within Group A and Group B(p&lt;0.01) but there is no significant improvement between both groups (p=0.150). Thus,the study concludes DJ and CMJ plyometric are worthwhile training activities for improving leg muscle power in young athletes.

Characteristics of the stretch-shortening cycle movement ability of male field hockey players

Characteristics of the stretch-shortening cycle movement ability of male field hockey players

Characteristics of force and power outputs during the trunk-twist exercise accompanying stretch-shortening cycle movement

Characteristics of force and power outputs during the trunk-twist exercise accompanying stretch-shortening cycle movement

Evaluation of stretch-shortening cycle movement by the multistep drop jump test using different drop heights

Evaluation of stretch-shortening cycle movement by the multistep drop jump test using different drop heights

Lower Leg Morphology and Stretch-Shortening Cycle Performance of Dancers.

Greater levels of bone ultimate fracture load, bone stress-strain index, muscle cross-sectional area, and maximal voluntary isometric plantarflexion (MVIP) strength of the lower leg may be adaptations from chronic exposure to stretch-shortening cycle (SSC) actions. Dancers, a population that habitually performs SSC movements primarily about the ankle joint, may serve as a novel population to gain broader understanding of SSC function. A total of 10 female collegiate dancers and 10 untrained controls underwent peripheral quantitative computed tomography scans of both lower legs and performed MVIPs, countermovement hops, and drop hops at 20, 30, and 40cm on a custom-made inclined sled. Dancers had greater right and left ultimate fracture load values and significantly (P ≤ .05) greater left leg stress-strain index than controls. Dancers had significantly larger right and left muscle cross-sectional area and MVIP values and hopped significantly higher during all hopping conditions in comparison with controls. Average force-time and power-time curves revealed significantly greater relative force and power measurements during the concentric phase for all hopping conditions in dancers when compared with controls. This investigation provides evidence that dance may be a stimulus for positive muscle and bone adaptations, strength levels, and enhanced SSC capabilities.

Effects of resistance training using known vs unknown loads on eccentric-phase adaptations and concentric velocity.

The aims of this study were to compare both eccentric- and concentric-phase adaptations in highly trained handball players to 4weeks of twice-weekly rebound bench press throw training with varying loads (30%, 50% and 70% of one-repetition maximum [1-RM]) using either known (KL) or unknown (UL) loads and to examine the relationship between changes in eccentric- and concentric-phase performance. Twenty-eight junior team handball players were divided into two experimental groups (KL or UL) and a control group. KL subjects were told the load prior each repetition, while UL were blinded. For each repetition, the load was dropped and then a rebound bench press at maximum velocity was immediately performed. Both concentric and eccentric velocity as well as eccentric kinetic energy and musculo-articular stiffness prior to the eccentric-concentric transition were measured. Results showed similar increases in both eccentric velocity and kinetic energy under the 30% 1-RM but greater improvements under 50% and 70% 1-RM loads for UL than KL. UL increased stiffness under all loads (with greater magnitude of changes). KL improved concentric velocity only under the 30% 1-RM load while UL also improved under 50% and 70% 1-RM loads. Improvements in concentric movement velocity were moderately explained by changes in eccentric velocity (R2 =.23-.62). Thus, UL led to greater improvements in concentric velocity, and the improvement is potentially explained by increases in the speed (as well as stiffness and kinetic energy) of the eccentric phase. Unknown load training appears to have significant practical use for the improvement of multijoint stretch-shortening cycle movements.

Evaluation of the effect of an acupuncture stimulation on an index to evaluate the ability using the stretch-shortening cycle movement in the lower limbs

Evaluation of the effect of an acupuncture stimulation on an index to evaluate the ability using the stretch-shortening cycle movement in the lower limbs

Relationship Between Jump Rope Double Unders and Sprint Performance in Elementary Schoolchildren.

According to dynamic analyses of muscle contraction, jump rope is a typical stretch-shortening cycle (SSC) movement. It has been reported that the relationship with SSC is higher in double unders than in single unders (basic jumps); however, the relationship between jump rope and sprint performances has not been extensively studied. To clarify this relationship in elementary schoolchildren, we compared the sprint speed and SSC ability of children who were grouped according to gender and ability. The subjects were 143 elementary fifth and sixth graders (78 boys, 65 girls). The consecutive maximal number of double unders, reactivity index (index of SSC ability) by Myotest, and 20-m sprint time were measured. According to the mean of jump rope records, the children were divided into a superior ability group (more than average + 0.5 SD) and an inferior ability group (less than average - 0.5 SD) for each gender. In both genders, a significant difference was found in the 20-m sprint time between the inferior and superior ability groups. The times for the superior ability groups (boys, 3.75 ± 0.23 seconds; girls, 4.02 ± 0.24 seconds) were excellent compared with the inferior ability groups (boys, 4.17 ± 0.32 seconds; girls, 4.23 ± 0.21 seconds). This effect size was higher in boys (1.44) than in girls (0.93). The reactivity index in the superior ability group was excellent compared with that in the inferior ability group. In conclusion, children who perform better in double unders are also faster during a 20-m sprint run. This tendency may be higher in boys. Classic jump rope training, such as double unders, should be effective as elementary plyometrics for improving the sprint ability of children.

Effect of surface stiffness on the neural control of stretch-shortening cycle movements.

It is accepted that leg stiffness (Kleg ) increases when surface stiffness decreases, and vice versa. However, little is known how the central nervous system fulfils this task. To understand the effect of surface stiffness on the neural control of stretch-shortening cycle movements, this study aimed to compare modulation of spinal and corticospinal excitability at distinct phases after ground contact during two-legged hopping when changing from solid to elastic ground. Motor-evoked potentials (MEPs) induced by transcranial magnetic stimulation (TMS) and H-reflexes were elicited at the time of the short (SLR)-, medium (MLR)- and long (LLR)-latency responses of the soleus muscle (SOL) during two-legged hopping on different stiffness surfaces, elastic and stiff. Soleus H-reflexes during two-legged hopping on the elastic surface were lower at SLR and larger at LLR than on the stiff surface (P < 0.05 for both comparisons). SOL MEP size was higher at the time of SLR during hopping on the elastic surface than on the stiff surface (P < 0.05) although the background EMG was similar. It is argued that this phase-specific adaptation in spinal reflex excitability is functionally relevant to adjust leg stiffness to optimally exploit the properties of the elastic surface. Thus, the increased corticospinal excitability on the elastic surface may reflect a more supraspinal control of the ankle muscles to compensate the decrease in reflexive stiffness at the beginning of touchdown and/or counteract the higher postural challenges associated with the elastic surface.

Possibility of Stretch-Shortening Cycle Movement Training Using a Jump Rope

Although jumping rope has been said to be a typical stretch-shortening cycle movement (SSC) from the dynamic analysis of muscle contraction, there are few research reports that focus on this point. Recently, the function of SSC of the legs with respect to the jumping movement has been evaluated using the rebound jump index (RJ-index). This study aimed to examine the possibility of using rope jumping in SSC training by comparing the RJ-index of the rebound jump (standard value) and the 2 different methods of rope jumping. The subjects included 76 healthy young men. Most subjects were involved in routine sports training 2-3 times per week. They performed the rebound jump (5 consecutive vertical jumps) and both a basic and a double-under jump with the jump rope, according to each participant's individual style (rhythm or timing). The RJ-index was calculated using the ground contact time and the jump height. The reliabilities of the RJ-index in the basic (intraclass correlation coefficient: 0.85) and double-under jump (0.92) were high, and the RJ-index of the latter (1.34 ± 0.24) was significantly higher than that of the former (0.60 ± 0.21). In the case of a group with inferior SSC ability, the RJ-index of the rebound jump only showed a significant correlation with the double-under but not with the basic jump. When using the RJ-index (1.97 ± 0.38) of the rebound jump as a criterion, the double-under-using about 70% of the SSC ability-may be effective for reinforcement of SSC ability.

リバウンドロングジャンプ指数の優劣を決定する踏切局面の技術的要因

The present study was conducted to examine the most effective takeoff movement for the Rebound Long Jump Test (RLJ test) under high-speed conditions. This test is designed to evaluate the ability to perform the ballistic stretch-shortening cycle movement for unilateral horizontal jump events on the basis of the RLJ index (RLJ index (m/s)=Jumping distance (JD (m))/Contact time (CT (s)). Subjects jump from a 0.1-m-high step to the ground after an approach run (falling jump), followed by jumping without interruption for as far as possible (propulsive jump). Eleven male college track-and-field athletes performed the RLJ test, and the RLJ index was calculated. On the basis of the average value of the RLJ index, the athletes were assigned to an upper level group (RLJ index>mean value) or a lower level group (RLJ index<mean value), and the takeoff movement of upper level group was considered the effective takeoff movement. The results suggested that it was important to minimize the rotation angle of the body, and to use a faster rotation velocity. This was achieved by 1) increasing the movement distance and velocity in the direction of the forward movement of the swing leg in the air, 2) minimizing the rotation angle of the foot and shank segment, and increasing that of the thigh segment during the initial phase, and 3) accelerating the rotation angle of the thigh segment again and swinging the swing-leg forward and up during the latter phase. These results suggest that the RLJ test and RLJ index provide a measure of the takeoff movement technique in terms of pre-rotation moment, the mechanism of rotation of the lower limb segment, and the swing moment of the swing leg.

大学野球投手における体幹の伸張-短縮サイクル運動および動作が投球速度に与える影響

The present study measured isometric muscular strength and mean power elicited by trunk twisting and trunk rotation during pitching in 28 university baseball pitchers aged 18-22 years. Based on the correlations among these measurements, the purpose of the study was to clarify 1) the influence of ball velocity on isometric muscular strength, trunk power output during the stretch-shortening cycle (SSC) and trunk rotation during pitching and 2) the influence of augmentation which is an index of SSC elicited by trunk rotation on trunk rotation during pitching. We also determined mean power and augmentation during concentric (CT) and SSC rebound (RT) throws of medicine balls weighing 5 kg while twisting the trunk. Augmentation while throwing the medicine ball was positively correlated with ball velocity (r=0.619, p<0.01), and augmentation of the medicine ball was positively correlated with torso rotation velocity at 18-27% and at 46-75% (r=0.398-0.542, p<0.05), and trunk twist velocity at 60-66% (r=0.378-0.395, p<0.05) of the second phase (from stride foot contact to instant release of the ball) during the pitching motion. In addition, pitched ball velocity was positively correlated with the velocities of pelvic rotation at 37-78% (r=0.378-0.488, p<0.05), torso rotation at 46-87% (r=0.391-0.711, p<0.05) and trunk twist at 63-83% (r=0.375-0.499, p<0.05) during the second phase of the pitching motion. These results indicate that pitchers with a larger ball velocity can use SSC movement generated by twisting the trunk, which effectively increases trunk rotation from the first half to middle of the second phase, and they can also increase trunk rotation during the second phase.

水平片脚跳躍を用いたバリスティックな伸張-短縮サイクル運動の遂行能力と各種跳躍パフォーマンスとの関係

The purpose of this study was to develop a new method for measuring the common ability to perform the ballistic stretch-shortening cycle movement in unilateral horizontal jump events and to investigate the relationship between the performances of various jump events. Ten male college track and field athletes performed the rebound long jump test (RLJ test). The participants jumped from a 0.1-m-high step to the ground after an approach run (falling jump), followed by jumping without interruption for as far as possible (propulsive jump). The falling jump distance was set at 1, 2, or 3 m, and touchdown velocity, jumping distance, contact time, ground reaction force and leg joint torque were measured for all three falling jump distances. To evaluate RLJ test performance, the RLJ index was calculated by dividing jumping distance by contact time. Simultaneously, the rebound jump test (RJ test) method for measuring the common ability to perform the ballistic stretch-shortening cycle movement in lateral vertical jump events and the five steps of bounding (5SB) method for measuring the common ability to perform unilateral horizontal jump events were conducted. We found that there were no significant correlations between the jumping height, contact time, and RJ power [RJ power (W/kg)=jumping height (m)/(contact time (sec)/2)] of the RJ test and the jumping distance, contact time, and RLJ index of the RLJ test, or any of the three falling jump distances. Thus, it was concluded that abilities to perform those two tests differed. On the other hand, there was a strong correlation (r=0.859) between the RLJ index measured for a falling jump distance of 3 m (RLJ index3) and the IAAF score of track and field athletes. In addition, the pattern and magnitude for the ground reaction force and leg joint torque measured during the RLJ for a falling jump distance of 3 m had similar characteristics to takeoff in the long jump or triple jump during a competition. Furthermore, 5SB was correlated (r=0.790) with the IAAF score, but the correlation coefficient was less than that of the RLJ index3. The RJ index was not correlated with the IAAF score. These results demonstrate the significance of using the RLJ test and RLJ index from a 0.1-m-high step for measuring the common ability to perform the ballistic stretch-shortening cycle movement in unilateral horizontal jump events.

Potentiation of Concentric Force and Acceleration Only Occurs Early During the Stretch-Shortening Cycle

The purpose of this study was to determine where stretch-shortening cycle (SSC) potentiation of force, power, velocity, and acceleration occurs across the concentric phase of ballistic leg presses. Second, we examined the influence of late eccentric phase force and length of the amortization phase on potentiated concentric phase performance variables. Twenty-one male runners (age: 31.9 ± 4.7 years) performed SSC and concentric-only (CO) ballistic leg press throws. Potentiations of concentric actions were calculated as the difference between SSC and CO contractions. An analysis splitting the concentric range of motion (ROM) into 6 equal time intervals determined force and acceleration were potentiated (p < 0.05) only during the first one-sixth time interval of concentric motion, whereas velocity and power were potentiated (p < 0.05) at all time intervals over the entire concentric motion with the exception of power over the last one-sixth time interval. A more precise analysis examining 20-millisecond time intervals across the first 200 milliseconds of concentric motion determined force was potentiated only over the first 140 milliseconds and acceleration only over the first 160 milliseconds. Eccentric force measured during the last 100 milliseconds of eccentric motion was related to potentiated force during the initial 200 milliseconds of concentric motion (r = 0.44, p < 0.05) and potentiated mean power across the full concentric ROM (r = 0.62, p < 0.01). Results indicate that in contrast to power and velocity, potentiation of force and acceleration occurs only early during the concentric phase of SSC ballistic leg presses. Correlational findings imply late eccentric phase force is important for generating force and power during the concentric phase of the SSC and thus training focusing on enhancing late phase eccentric force appears important for developing explosive force and power during SSC movements.

Neuromuscular fatigue recovery following rapid and slow stretch–shortening cycle movements

The purpose of this study was to investigate underlying mechanisms and neuromuscular recovery patterns following rapid and slow stretch-shortening cycle (SSC) movements performed to fatigue. Fourteen (10 moderately trained (MT) and four highly trained (HT)) subjects completed rapid and slow SSC movements to fatigue. The rapid SSC movement consisted of continuous drop jumps from a 30 cm platform until a predetermined jump height was no longer maintained, and the slow SSC movement consisted of continuous squats to 90° of knee flexion at a load of 65% of subject's one-repetition maximum until no further repetitions could be completed. Although blood lactate measures were significantly (p < 0.002) higher after the rapid SSC condition versus after the slow SSC condition, the recovery of neuromuscular properties (maximum voluntary contractions, twitch force, muscle compound action potential) following the two conditions to fatigue did not differ. The duration of the rapid SSC movement was dependent on the training status of the subject; HT subjects performed the rapid SSC longer (68.2%) than the MT subjects until fatigued. Thus, the neuromuscular fatigue recovery patterns were independent of the type of SSC movement, condition duration, and subject training status. Because rapid and slow SSC exercises induce similar fatigue patterns, training programs incorporating rapid SSC exercises can be developed similar to that prescribed in traditional slow SSC resistance training programs.