Squat Jump Performance Research Articles

Effect of heavy strength training on muscle thickness, strength, jump performance, and endurance performance in well-trained Nordic Combined athletes

The purpose of the present study was to investigate the effect of supplemental heavy strength training on muscle thickness and determinants of performance in well-trained Nordic Combined athletes. Seventeen well-trained Nordic Combined athletes were assigned to either usual training supplemented with heavy strength training (STR; n = 8) or to usual training without heavy strength training (CON; n = 9). The strength training performed by STR consisted of one lower-body exercise and two upper-body exercises [3-5 repetition maximum (RM) sets of 3-8 repetitions], which were performed twice a week for 12 weeks. Architectural changes in m. vastus lateralis, 1RM in squat and seated pull-down, squat jump (SJ) height, maximal oxygen consumption (VO(2max)), work economy during submaximal treadmill skate rollerskiing, and performance in a 7.5-km rollerski time trial were measured before and after the intervention. STR increased 1RM in squat and seated pull-down, muscle thickness, and SJ performance more than CON (p < 0.05). There was no difference between groups in change in work economy. The two groups showed no changes in total body mass, VO(2max), or time-trial performance. In conclusion, 12 weeks of supplemental strength training improved determinants of performance in Nordic Combined by improving the athletes' strength and vertical jump ability without increasing total body mass or compromising the development of VO(2max).

Whole-Body Vibration Training Effects on the Physical Performance of Basketball Players

The aim of this study was to investigate the influence of 4 weeks of whole-body vibration training added to the conventional training of basketball players. Eighteen competitive basketball players (13 male symbol, 5 female symbol, 18-24 years old) were randomly assigned to a whole-body vibration group (WBVG, n = 10; 7 male symbol and 3 female symbol) or a control group (CG, n = 8; 6 male symbol and 2 female symbol). During the 4-week period, all subjects maintained their conventional basketball training program. The members of WBVG were additionally trained 3 times a week for 20 minutes on a vibration platform (10 unloaded static lower limb exercises, 40-Hz, 4-mm, Silverplate). Testing was performed before and after the 4-week period and comprised strength assessment, vertical jump performance, and a 10-m sprint test. The maximal voluntary isometric strength of the knee extensors significantly increased (p < 0.001) after vibration training, as did squat jump (SJ) height (p < 0.05), whereas performance of the countermovement jump, drop jump, 30-second rebound jump, and 10-m sprint remained unchanged. The results of the present study indicated that a 4-week whole-body vibration training program added to the conventional training of basketball players during the preseason is an effective short-term stimulus to enhance knee extensor strength and slightly SJ performance.

Acute Effects of Static Stretching on Squat Jump Performance at Different Knee Starting Angles

The purpose of this study was to examine the effects of static stretching on leg extensor muscles during squat jump (SJ) at different knee starting angles. Seventeen male subjects (23 +/- 3 years, 179 +/- 5 cm, and 74 +/- 6 kg) performed on a force platform 2 series (preceded or not [control condition] by 10-minute static stretching of quadriceps and triceps surae muscles) of SJs at different knee starting angles: 50 degrees, 70 degrees, 90 degrees, and 110 degrees. Squat jump height, peak force, maximal acceleration, velocity, and power were calculated for each jump. The angle that maximized power development was obtained from the power-angle relationship. The SJ height, peak force, and maximal velocity increased according to angle amplitude in both control and stretching conditions (p < 0.01), performance being significantly lower in the stretching condition (p < 0.01). Peak power was obtained at 90 degrees in both control and stretching conditions, but was significantly lower (p < 0.01) after stretching. These results suggest that an acute bout of static stretching reduces power and force development during SJ, decrements being significantly higher at lower knee starting angles. Therefore, the use of static stretching may be questionable in those power activities requiring maximal power output at knee angles near full extension.

Overload Creatine Supplementation Effect On Volleyball Players Strength

PURPOSE: To determine the effects of overload oral creatine supplementation during 7 days, on strength gain and delayed muscle fatigue of Volleyball players. METHODS: Twenty four male Volleyball players, with an average age of 21.4 yrs (±2.4) took part in this study: 12 constituted the placebo group (PG) and ingested 20 g of manitol per day, and the others ingested 20 g of creatine monohydrate (CG) per day, distributed by four doses of 5 g each (in the morning, after lunch and before and immediately after the training). To measure strength levels, all the athletes performed a Squat Jump (SJ) and a Counter Movement Jump (CMJ) in the Ergo Jump (Globus Ergo Tester) at the beginning and in the end of the training session, both before the supplementation program started (pretest) and after 7 days (posttest). The groups' strength levels comparisons between pretest and posttest and between the beginning and the end of each training session were made using two-way ANOVA with repeated measures. RESULTS: There were no differences in SJ performance between pretest and posttest either in PG (0.64 + 0.04 vs. 0.66 + 0.07 at beginning, and 0.64 + 0.05 vs. 0.65 + 0.04 at the end of training session) or in CG (0.60 + 0.07 vs. 0.59 + 0.09 at beginning, and 0.59 + 0.07 vs. 0.61 + 0.06 at the end of training session). Similarly, there were no differences in CMJ performance between pretest and posttest either in PG (0.65 + 0.04 vs. 0.67 + 0.03 at beginning, and 0.66 + 0.03 vs. 0.66 + 0.03 at the end of the training session) or in CG (0.61 + 0.07 vs. 0.60 + 0.08 at beginning, and 0.60 + 0.07 vs. 0.61 + 0.07 at the end of the training session). CONCLUSIONS: The overload creatine supplementation failed to induce an increase in strength gain and delayed muscle fatigue of Volleyball players.

Acute neuromuscular and hormonal responses during contrast loading: Effect of 11 weeks of contrast training

The purpose of this study was to assess (1) acute neuromuscular and endocrine responses during a contrast loading protocol and (2) how these acute responses are possibly influenced by 11 weeks of contrast training. Contrast loading tests consisting of 4 sets of 80% 1 RM back squat and 4 sets of squat jump (SJ) were performed before and after training. Bilateral isometric leg extension (LE) assessed the impact of loading on isometric variables pre-, mid-, and post-loading. Potentiated SJ performance was observed in set 2 (4.6%, P<0.05), before training only. Greater indications of fatigue were observed in SJ, isometric force, and vastus lateralis (VL) activation after training (P<0.05). Training-induced improvements in SJ height, 80% 1 RM squat load, and maximum isometric LE force were observed (12%, 10%, and 7.7%, P<0.05). In conclusion, potentiated SJ performance occurred during a typical contrast loading protocol before the training period. However, potentiated SJ performance may alter through training, and therefore, the responsiveness of the individual should be periodically monitored and training protocols updated when necessary.

Acute Effects of Heavy-Load Exercises, Stretching Exercises, and Heavy-Load Plus Stretching Exercises on Squat Jump and Countermovement Jump Performance

The purpose of this study was to examine the acute effects of heavy-load resistance exercises, static stretching exercises, and heavy-load plus static stretching exercises by untrained subjects, and to determine whether these types of exercise have an effect on the performance of squat jumps (SJs) and countermovement jumps (CMJs). Twenty-four men volunteered to participate in this study and were divided into 3 groups: 1 group performed the strength exercises using heavy loads (3 sets of 4 repetitions at 90% of each subject's 1-repetition maximum (1RM), a second group performed the heavy-load resistance plus stretching exercises (3 sets of 4 repetitions at 90% of each subject's 1RM and 3 stretching exercises for 15 seconds each), and a third group performed the static stretching exercises only (3 stretching exercises for 15 seconds each). No significant differences between the groups were seen in vertical jump height, but there were significant differences (p < 0.004) in the mean jump height between sets within the training session without taking the treatment type (group) into consideration. Significant differences (p < 0.001) were seen in the vertical ground-reaction force in CMJs between sets and training in each group, whereas no differences between groups were seen in SJ; nevertheless, there was a tendency toward significant differences between sets (p < 0.09) without considering the treatment type. The data from this study suggest that strength exercises using heavy loads and heavy-load plus stretching exercises did not have a significant effect on the maximal jump height in untrained subjects. Only stretching exercises showed an increase in SJs and CMJs, but these results were not significantly different from all other scores.

Squat Jump Performance During Growth in Both Sexes

The purpose of this cross-sectional study was to investigate leg muscle power and compare two activities (jumping and cycling) in 383 girls and 407 boys ages 9–19 years. Results in anthropometric characteristics and jumping performance were comparable until midadolescence, and sex differences were observed. Lean leg volume (LLV) was the reason for most of the variance (76% in girls and 88% in boys) in jumping performance. However, the LLV exponent was higher than expected in boys but not girls. Therefore, unidentified qualitative changes of muscle function during growth in boys must be considered. The squat jump index (SJI) was highly correlated to cycling peak power (CPP; N = 790, r = .94, p < .001). Although prediction error of CPP from SJI was less than 5% when considering each sex-and-age group, individual errors mounted to 40%. Due to its practicability, SJI is recommended in large-scale developmental prospective studies. However, cycling and jumping protocols are not interchangeable when measuring peak power values.

Acute Effects of Heavy-Load Squats on Consecutive Squat Jump Performance

Postactivation potentiation (PAP) and complex training have generated interest within the strength and conditioning community in recent years, but much of the research to date has produced confounding results. The purpose of this study was to observe the acute effects of a heavy-load back squat [85% 1 repetition maximum (1RM)] condition on consecutive squat jump performance. Twelve in-season Division I male track-and-field athletes participated in two randomized testing conditions: a five-repetition back squat at 85% 1RM (BS) and a five-repetition squat jump (SJ). The BS condition consisted of seven consecutive squat jumps (BS-PRE), followed by five repetitions of the BS at 85% 1RM, followed by another set of seven consecutive squat jumps (BS-POST). The SJ condition was exactly the same as the BS condition except that five consecutive SJs replaced the five BSs, with 3 minutes' rest between each set. BS-PRE, BS-POST, SJ-PRE, and SJ-POST were analyzed and compared for mean and peak jump height, as well as mean and peak ground reaction force (GRF). The BS condition's mean and peak jump height and peak GRF increased 5.8% +/- 4.8%, 4.7% +/- 4.8%, and 4.6% +/- 7.4%, respectively, whereas the SJ condition's mean and peak jump height and peak GRF decreased 2.7% +/- 5.0%, 4.0% +/- 4.9%, and 1.3% +/- 7.5%, respectively. The results indicate that performing a heavy-load back squat before a set of consecutive SJs may enhance acute performance in average and peak jump height, as well as peak GRF.

Squat Jump Performance During Growth in Both Sexes: Comparison With Cycling Power

Squat Jump Performance During Growth in Both Sexes: Comparison With Cycling Power

The Effects of a Twenty-Four–Week Aquatic Training Program on Muscular Strength Performance in Healthy Elderly Women

The purpose of the present study was to determine the effectiveness of a 24-week aquatic training (AT) program, which included both aerobic and resistance components, on muscle strength (isometric and dynamic), flexibility, and functional mobility in healthy women over 60 years of age. Twenty-two subjects were assigned randomly to either an AT (n = 12) or a control (C, n = 10) group. Volunteers participated in a supervised shallow-water exercise program for 60 minutes a day, 3 days a week; the exercise program consisted of a 10-minute warm-up and stretching, 25 minutes of endurance-type exercise (dancing) at 80% of heart rate (HR)(max), 20 minutes of upper- and lower-body resistance exercises with specialized water-resistance equipment, and a 5-minute cool down. Maximal isometric torque of knee extensors (KEXT) and knee flexors (KFLEX) were evaluated by a Cybex Norm dynamometer, grip strength (HGR) was evaluated using a Jamar hydraulic dynamometer, and dynamic strength was evaluated via the 3 repetition maximum (3RM) test for chest press, knee extension, lat pull down, and leg press. Jumping performance was evaluated using the squat jump (SJ), functional mobility with the timed up-and-go (TUG) test, and trunk flexion with the sit-and-reach test. Body composition was measured using the bioelectrical impedance method. The AT induced significant improvements in KEXT (10.5%) and KFLEX (13.4%) peak torque, HGR strength (13%), 3RM (25.7-29.4%), SJ (24.6%), sit-and-reach (11.6%), and TUG (19.8%) performance. The AT group demonstrated a significant increase in lean body mass (3.4%). No significant changes in these variables were observed in the C group. The results indicate that AT, with both aerobic and resistance components, is an alternative training method for improving neuromuscular and functional fitness performance in healthy elderly women.

Effect of Plyometric Training on Running Performance and Vertical Jumping in Prepubertal Boys

The purpose of this study was to investigate the effect of plyometric training on running velocity (RV) and squat jump (SJ) in prepubescent boys. Fifteen boys (11.1 +/- 0.5 years) followed a 10-week plyometric program (JUMP group). Another group of 15 boys (10.9 +/- 0.7 years) followed only the physical education program in primary school and was used as the control group (CONT group). Running distances (0-10 m, 10-20 m, 20-30 m, and 0-30 m), were selected as testing variables to evaluate the training program. The total number of jumps was initially 60 per session, which was gradually increased over a period of 10 weeks to 100 per session. Results revealed significant differences between CONT and JUMP groups in RV and SJ. In JUMP group the velocity for the running distances 0-30, 10-20, and 20-30 m increased (p < 0.05), but not for the distance 0-10 m (p > 0.05). Additionally, the SJ performance of the JUMP group increased significantly, as well (p < 0.05). There was no change in either RV or SJ for the CONT group. These results indicate that plyometric exercises can improve SJ and RV in prepubertal boys. More specifically, this program selectively influenced the maximum velocity phase, but not the acceleration phase.

Effect Of Stretch-shortening Cycle Exercises On The Mechanical And Neuromuscular Properties

PURPOSE To compare the effects of Stretch-Shortening Cycle (SSC) exercises on the mechanical and neuromuscular properties during the vertical jump for non-experienced jumpers and experienced jumpers. METHODS Sixteen subjects were recruited for the experiments. The First group (EJ), had at least 10 years of experience in jump training and therefore constituted experienced jumpers. The second group (NEJ) had at least five years of experience in the college sports but no prior experience in jump training. For the fatigue exercise, subjects were instructed to perform a long lasting SSC exercises inducing 50% of decraese in Maximal Isometric Force (MVC). For the testing protocols a leg press was used to measure isometric force and dynamic concentric movements at 40%, 50% and 60% of each subject's 1RM. A force plate was used to measure force, power, and height during the squat jump (SJ) and the countermovement jump (CMJ) on both feet. A 3-D system was used to analyze kinematic data for the most prominent protuberance of the hip greater trochanter, lateral femoral epicondyle of the knee, and the ankle lateral maleolus during each jumping exercises. Joint moment and stiffness of the knee was calculated using an inverse dynamics approach given segmental displacements, velocities, and accelerations obtained from the kinematic record and the force plate data. Myoelectric signals were recorded for the following muscles: vastus medialis, vastus lateralis, and biceps femoris for the jumping and leg press exercises. RESULTS For both groups, the SSC exercise suppressed voluntary isometric force and maximal concentric power (p<0.0006) and SJ performance (p<0.008) while only the experienced jumpers maintained their performance during the CMJ after fatigue exercise. EMG analysis (as interpreted through the root mean square and mean power frequency values) showed that the maximal concentric power, SJ and CMJ were performed similarly before and after the fatigue exercise for both the EJ and NEJ groups. CONCLUSIONS The major finding in our study was that non-experienced and experienced jumpers differ in their patterns of fatigue (as interpreted through the jump performance findings and the kinematic data). It appears that for the experienced jumpers, fatiguing the knee extensor did not affect the CMJ height. The experienced jumpers re-optimize knee extensor muscle recruitment by altering their jump strategy during the CMJ (as interprted through the increase in the eccentric and transition phases). Exhausting SSC exercise induced local muscle impairment and a decrease in muscle performance, which is not simply a direct effect of central command fatigue.

Influence of figure skating skates on vertical jumping performance

The purpose of this study was to investigate the influence of wearing figure skating skates on vertical jump performance and interjoint co-ordinations described in terms of sequencing and timing of joint rotations. Ten national to international figure skaters were filmed while performing a squat jump (SJ) on a force platform. Three experimental conditions were successively realized: barefoot (BF), lifting a 1.5 kg weight (LW) corresponding to the skates’ mass, attached on the distal extremity of each leg and wearing skates (SK). Jump height, angular kinematics as well as joints kinetics were calculated. Relative to the SJ height reached in the BF condition, SJ performance was significantly decreased by 2.1 and 5.5 cm in the LW and SK conditions, respectively. The restriction of ankle amplitude imposed by wearing skates was found to significantly limit the knee joint amplitude while the hip angular motion was not affected. Neither the skates’ mass nor the limited ankle angular motion modified the proximo-distal organization of joint co-ordination observed when jumping barefoot. However, with plantar flexion restriction, the delay between hip and knee extensions increased while it was reduced between knee and ankle extensions. Work output at the knee and ankle joints were significantly lowered when wearing skates. The decrease of work at the knee was shown to result from an early flexing moment causing a premature deceleration of the knee and from a reduction of knee amplitude. Taken together, these results show a minimization of the participation of the knee when plantar flexion is limited. It was proposed that constraining the distal joint causes a reorganization of interjoint co-ordinations and a redistribution of the energy produced by knee extensors to the hip and ankle joints.

Dependence of human squat jump performance on the series elastic compliance of the triceps surae: a simulation study.

The purposes of this study were to determine the dependence of human squat jump performance on the compliance of series elastic elements (SEEs) of the triceps surae (consisting of the soleus and gastrocnemius) and to explain this dependence. Vertical squat jumps were simulated using an optimal control model of the human musculo-skeletal system. Maximum jump height was found for several values of triceps surae SEE strain at maximum isometric force (epsilon(0)). When epsilon(0) was increased from 1 to 10 %, maximum jump height increased by 8 cm. This was partly due to a higher work output of contractile elements (CEs) of the muscles, primarily of the soleus, and also partly to an increased efficacy of converting muscle work to energy contributing to jump height. The soleus produced more work at epsilon(0)=10 % because, as a result of SEE recoil, the CE covered its shortening range at lower velocity and hence produced more force. Efficacy was higher at epsilon(0)=10 % because a higher vertical velocity at take-off was achieved with a lower rotational energy of the body segments. This apparent discrepancy was explained by increased angular velocities of the shanks and feet, which have small moments of inertia, and decreased angular velocities of the thighs and trunk, which have larger moments of inertia. This redistribution of segmental contributions to the vertical velocity of the centre of mass was possible because the increased compliance of the triceps surae SEE enhanced the energy-buffering capacity of this muscle group and, thereby, allowed for a higher power output at the ankles. It seems that long compliant tendons in the plantar flexors are an elegant solution to the problem of maximizing jumping performance.

The effects of electromyostimulation training and basketball practice on muscle strength and jumping ability.

The aim of this study was to investigate the influence of a 4-week electromyostimulation training program on the strength of the knee extensors and the vertical jump performance of 10 basketball players. Electromyostimulation sessions were carried out 3 times weekly; each session consisted of 48 contractions. Testing was carried out before and after the electromyostimulation training program (week 4) and once more after 4 weeks of normal basketball training (week 8). At week 4, isokinetic strength increased significantly (p < 0.05) at eccentric and high concentric velocities (between 180 and 360 x s(-1)); this was not the case for low concentric velocities (60 and 120 degrees x s(-1)). Electromyostimulation training increased also isometric strength at the two angles adjacent to the training angle (p < 0.01). Squat jump increased significantly by 14% at week 4 (p < 0.01), whereas counter movement-jump showed no change. At week 8, gains in isokinetic, isometric strength and squat-jump performance were maintained and the counter movement jump performance increased significantly by 17% (p<0.01). Electromyostimulation as part of a short strength-training program enhanced knee extensor strength and squat jump performance of basketball players.

Effects of the type of recovery training on the concentric strength of the knee extensors

The aim of this study was to examine the effects of specific concentric and eccentric training on concentric muscular strength following an initial standardized period of excessive training that combined concentric and eccentric actions. For a period of 12 weeks, 37 young elite female basketball players performed standardized training, which included concentric and eccentric actions at 70% and 110% of one-repetition maximum (1-RM), respectively. They were then divided into three groups that followed 12 week programmes which included concentric (C-E/C, n = 13), eccentric (C-E/E, n = 13) or a combination of both concentric and eccentric (C-E/C-E, n = 11) exercises. The standardized and specific training programmes consisted of 16 and 8 sets of eight repetitions respectively, performed four times a week. Eleven players who did not participate in either the standardized or specific training programmes served as controls (n = 11). Following the initial 12 weeks of standardized training, the concentric strength of the knee extensors was evaluated isokinetically and using leg-press and squat-jump tests. Significant (P < 0.05) reductions in isokinetic torque, and leg-press and squat-jump performance, were seen. The C-E/C group showed significant (P < 0.05) increases in isokinetic torque, and leg-press and squat-jump performance, after 24 weeks of training when compared with pretraining values. Conversely, no significant differences were noted for the C-E/E and C-E/C-E groups. These findings confirm the mode specificity principle, as only the concentric specific training programme improved the concentric strength of the knee extensors.