Changes in dynamic exercise performance following a sequence of preconditioning isometric muscle actions

Complex training is the method of coupling heavy and light loads into an organized sequence with the aim of facilitating postactivation potentiation. Anecdotal evidence has supported the use of complex training sequences, but scientific studies investigating the effects of sequencing isometric loads with dynamic muscle actions have been limited. The purpose of this study was to examine the effects of a preconditioning sequence of maximal isometric knee extensions on performance standards in selected dynamic whole-body exercise. Fourteen track and field athletes (23 +/- 5.7 years; 71.53 +/- 6.93 kg; 172.6 +/- 5.8 cm) were randomly assessed in selected whole-body exercises (drop and countermovement jumps, 5-second cycle sprint, knee extension) following a sequence of maximal voluntary isometric contractions (MVC; 3 repetitions of 3 seconds or 3 repetitions of 5 seconds) or in the absence of prior loading (control). Electromyographic (EMG) assessments of muscle activity were also made during the knee extension assessment. Significant (p < or = 0.05) increases in jump height (5.03%), maximal force (4.94%), and acceleration impulse (9.49%) were observed in the drop jump following 3 repetitions of 3-second MVC only. Knee extension maximal torque was also significantly increased (6.12%) following the 3-second MVC. No significant changes in countermovement jump or cycle sprint measures were observed for any of the experimental conditions. Though adaptations were found, changes in EMG activity were not significantly different for any of the experimental conditions. These data indicate that performing a sequence of repeated maximal isometric knee extensions (3 repetitions of 3 seconds) prior to selected dynamic exercise (< or =0.25 seconds) may have favorable effects on performance beyond standards achieved without prior heavy loading.     

Test-retest reliability of knee biomechanics during stop jump landings

Studies that seek to determine the effects of an intervention on knee biomechanics during landing from a jump implicitly assume that the variables of interest are reliable both within and between data collection sessions. Currently, such reliability data are not available for a stop jump. Standard three-dimensional motion analysis was used to determine sagittal and frontal plane peak angles and moments and peak vertical ground reaction force within and between sessions for a stop jump. Twelve female recreational athletes participated in two data collection sessions spaced two weeks apart. Interclass correlation coefficients and coefficient of multiple correlation were used to determine within and between session reliability of peak knee flexion angle, peak internal knee extension moment, peak knee abduction angle, peak internal knee adduction moment and peak vertical ground reaction force. Overall reliability within a session (ICC (3,1) 0.631-0.881; CMC 0.672-0.958) and between sessions (ICC (3,k) 0.685-0.959; CMC 0.598-0.944) was good. Peak angles and moments were similar between sessions. The stop jump is less reliable within a session than a drop vertical jump reported previously in the literature. This is likely due to increased intrasubject variability between trials due to the less constrained nature of the task. Reliability of the stop jump is comparable to the drop vertical jump between sessions. Reliability of knee adduction moment is lower than reported for the drop vertical jump. The results of this study support the use of a stop jump task to evaluate knee biomechanics during landing in longitudinal studies with a repeated measures design.     

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.     

Alterations to movement mechanics can greatly reduce anterior cruciate ligament loading without reducing performance

Anterior cruciate ligament (ACL) injuries are one of the most common and potentially debilitating sports injuries. Approximately 70% of ACL injuries occur without contact and are believed to be preventable. Jump stop movements are associated with many non-contact ACL injuries. It was hypothesized that an athlete performing a jump stop movement can reduce their peak tibial shear force (PTSF), a measure of ACL loading, without compromising performance, by modifying their knee flexion angle, shank angle, and foot contact location during landing. PTSF was calculated for fourteen female basketball players performing jump stops using their normal mechanics and mechanics modified to increase their knee flexion angle, decrease their shank angle relative to vertical and land more on their toes during landing. Every subject tested experienced drastic reductions in their PTSF (average reduction=56.4%) using modified movement mechanics. The athletes maintained or improved their jump height with the modified movement mechanics (an average increase in jump height of 2.5 cm). The hypothesis was supported: modifications to jump stop movement mechanics greatly reduced PTSF and therefore ACL loading without compromising performance. The results from this study identify crucial biomechanical quantities that athletes can easily modify to reduce ACL loading and therefore should be targeted in any physical activity training programs designed to reduce non-contact ACL injuries.     

Effects of electromyostimulation training and volleyball practice on jumping ability

The aim of this study was to investigate the influence of a 4-week electromyostimulation (EMS) training program on the vertical jump performance of 12 volleyball players. EMS sessions were incorporated into volleyball sessions 3 times weekly. EMS consisted of 20-22 concomitant stimulations of the knee extensor and plantar flexor muscles and lasted approximately 12 minutes. No significant changes were observed after EMS training for squat jump (SJ) and counter movement jump (CMJ) performance, while the mean height and the mean power maintained during 15 seconds of consecutive CMJs significantly increased by approximately 4% (p < 0.05). Ten days after the end of EMS training, the jumping height significantly (p < 0.05) increased compared with baseline also for single jumps (SJ +6.5%, CMJ +5.4%). When the aim of EMS resistance training is to enhance vertical jump ability, sport-specific workouts following EMS would enable the central nervous system to optimize the control to neuromuscular properties.     

Determination of functional strength imbalance of the lower extremities

The purposes of this study were (a) to determine whether a significant strength imbalance existed between the left and right or dominant (D) and nondominant (ND) legs and (b) to investigate possible correlations among various unilateral and bilateral closed kinetic chain tests, including a field test, and traditional isokinetic dynamometry used to determine strength imbalance. Fourteen Division I collegiate women softball players (20.2 +/- 1.4 years) volunteered to undergo measures of average peak torque for isokinetic flexion and extension at 60 degrees .s(-1) and 240 degrees .s(-1); in addition, measures of peak and average force of each leg during parallel back squat, 2-legged vertical jump, and single-leg vertical jump and performance in a 5-hop test were examined. Significant differences of between 4.2% and 16.0% were evident for all measures except for average force during single-leg vertical jump between the D and ND limbs, thus revealing a significant strength imbalance. The 5-hop test revealed a significant difference between D and ND limbs and showed a moderate correlation with more sophisticated laboratory tests, suggesting a potential use as a field test for the identification of strength imbalance. The results of this study indicate that a significant strength imbalance can exist even in collegiate level athletes, and future research should be conducted to determine how detrimental these imbalances could be in terms of peak performance for athletes, as well as the implications for injury risk.     

ACUTE EFFECTS OF A RESISTED DYNAMIC WARM-UP PROTOCOL ON JUMPING PERFORMANCE

This study aimed to investigate the kinematic and kinetic changes when resistance is applied in horizontal and vertical directions, produced by using different percentages of body weight, caused by jumping movements during a dynamic warm-up. The group of subjects consisted of 35 voluntary male athletes (19 basketball and 16 volleyball players; age: 23.4 ± 1.4 years, training experience: 9.6 ± 2.7 years; height: 177.2 ± 5.7 cm, body weight: 69.9 ± 6.9 kg) studying Physical Education, who had a jump training background and who were training for 2 hours, on 4 days in a week. A dynamic warm-up protocol containing seven specific resistance movements with specific resistance corresponding to different percentages of body weight (2%, 4%, 6%, 8%, 10%) was applied randomly on non consecutive days. Effects of different warm-up protocols were assessed by pre-/post- exercise changes in jump height in the countermovement jump (CMJ) and the squat jump (SJ) measured using a force platform and changes in hip and knee joint angles at the end of the eccentric phase measured using a video camera. A significant increase in jump height was observed in the dynamic resistance warm-up conducted with different percentages of body weight (p < 0.05). On the other hand, no significant difference in different percentages of body weight states was observed (p > 0.05). In jump movements before and after the warm-up, while no significant difference between the vertical ground reaction forces applied by athletes was observed (p > 0.05), in some cases of resistance, a significant reduction was observed in hip and knee joint angles (p < 0.05). The dynamic resistance warm-up method was found to cause changes in the kinematics of jumping movements, as well as an increase in jump height values. As a result, dynamic warm-up exercises could be applicable in cases of resistance corresponding to 6-10% of body weight applied in horizontal and vertical directions in order to increase the jump performance acutely.     

Online video-based resistance training improves the physical capacity of junior basketball athletes

ABSTRACT: Klusemann, MJ, Pyne, DB, Fay, T, and Drinkwater, EJ. Online Video-Based Resistance Training Improves the Physical Capacity of Junior Basketball Athletes. J Strength Cond Res 26(10): 2677-2684, 2012-Junior basketball athletes require a well-designed resistance training program to improve their physical development. Lack of expert supervision and resistance training in junior development pathways may be overcome by implementing an online video-based program. The aim of this study was to compare the magnitude of improvement (change) in physical performance and strength and functional movement patterns of junior basketball athletes using either a fully supervised or an online video-based resistance training program. Thirty-eight junior basketball athletes (males, n = 17; age, 14 ± 1 year; height, 1.79 ± 0.10 m; mass, 67 ± 12 kg; females, n = 21; age, 15 ± 1 year; height, 1.70 ± 0.07 m; mass, 62 ± 8 kg) were randomly assigned into a supervised resistance training group (SG, n = 13), video training group (VG, n = 13) or control group (CG, n = 12) and participated in a 6-week controlled experimental trial. Pre- and posttesting included measures of physical performance (20-m sprint, step-in vertical jump, agility, sit and reach, line drill, and Yo-Yo intermittent recovery level 1), strength (15 s push-up and pull-up), and functional movement screening (FMS). Both SG and VG achieved 3-5% ± 2-4% (mean ± 90% confidence limits) greater improvements in several physical performance measures (vertical jump height, 20-m sprint time, and Yo-Yo endurance performance) and a 28 ± 21% greater improvement in push-up strength compared with the CG. The SG attained substantially larger gains in FMS scores over both the VG (12 ± 10%) and CG (13 ± 8%). Video-based training appears to be a viable option to improve physical performance and strength in junior basketball athletes. Qualified supervision is recommended to improve functional movement patterns in junior athletes.     

Effects of differential stretching protocols during warm-ups on high-speed motor capacities in professional soccer players

The purpose of this study was to examine the effects of different modes of stretching within a pre-exercise warm-up on high-speed motor capacities important to soccer performance. Eighteen professional soccer players were tested for countermovement vertical jump, stationary 10-m sprint, flying 20-m sprint, and agility performance after different warm-ups consisting of static stretching, dynamic stretching, or no stretching. There was no significant difference among warm-ups for the vertical jump: mean +/- SD data were 40.4 +/- 4.9 cm (no stretch), 39.4 +/- 4.5 cm (static), and 40.2 +/- 4.5 cm (dynamic). The dynamic-stretch protocol produced significantly faster 10-m sprint times than did the no-stretch protocol: 1.83 +/- 0.08 seconds (no stretch), 1.85 +/- 0.08 seconds (static), and 1.87 +/- 0.09 seconds (dynamic). The dynamic- and static-stretch protocols produced significantly faster flying 20-m sprint times than did the no-stretch protocol: 2.41 +/- 0.13 seconds (no stretch), 2.37 +/- 0.12 seconds (static), and 2.37 +/- 0.13 seconds (dynamic). The dynamic-stretch protocol produced significantly faster agility performance than did both the no-stretch protocol and the static-stretch protocol: 5.20 +/- 0.16 seconds (no stretch), 5.22 +/- 0.18 seconds (static), and 5.14 +/- 0.17 seconds (dynamic). Static stretching does not appear to be detrimental to high-speed performance when included in a warm-up for professional soccer players. However, dynamic stretching during the warm-up was most effective as preparation for subsequent high-speed performance.     

Acute effects of different warm-up protocols with and without a weighted vest on jumping performance in athletic women

The purpose of this study was to examine the acute effects of 3 different warm-up protocols with and without a weighted vest on vertical jump (VJ) and long jump (LJ) performance in athletic women. Sixteen subjects (19.7 +/- 1.4 years, 67.0 +/- 10.7 kg, 165.7 +/- 11.4 cm) participated in 3 testing sessions in random order on 3 nonconsecutive days. Prior to the testing of the VJ and LJ, the subjects performed 1 of the following 10-minute warm-up protocols: (a) low- to moderate-intensity stationary cycling followed by 4 lower-body static stretches (SS) (3 x 20 seconds); (b) 12 moderate- to high-intensity dynamic exercises (DY); and (c) the same 12 dynamic exercises with a weighted vest (10% of body mass) worn for the last 4 exercises (DYV). Analysis of the data revealed that VJ performance was significantly greater (p < 0.05) following DYV (43.9 +/- 6.7 cm) and DY (43.6 +/- 6.5 cm) as compared to SS (41.7 +/- 6.0 cm). Long jump performance was significantly greater (p < 0.05) following DYV (186.8 +/- 19.5 cm) as compared to DY (182.2 +/- 19.1 cm), which in turn was significantly greater (p < 0.05) than performance following SS (177.2 +/- 18.8 cm). Warm-up protocols that include dynamic exercise may be a viable method of enhancing jumping performance in athletic women as compared to stationary cycling and static stretching. In addition, these data suggest that it may be desirable for athletic women to perform dynamic exercises with a weighted vest on some movements prior to the performance of the long jump.     

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.     

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.     

Gender bias in the effects of arms and countermovement on jumping performance

The ability to jump high is considered important in a number of sports. It is commonly accepted that the use of the arms and a counter movement increase jump height. In some sport situations (e.g., volley ball block, basketball rebound), athletes may not be able to utilize a counter movement or arm swing. The purpose of this study is to examine gender differences in the contribution of the arm swing and counter movement to vertical jump height. Fifty college students, 25 men (age = 21.4 +/- 1.7 years, height = 182.2 +/- 8 cm, weight = 83.7 +/- 12.4 kg) and 25 women (age = 20.7 +/- 1.6 years, height = 166.7 +/- 6.3 cm, weight = 61.5 +/- 7.0 kg), performed 4 jumping movements: squat jumps with hands on hips (SNA), counter movement jump with hands on hips (CMNA), squat jump with arm swing (SA), and counter movement with arm swing (CMA). Significant differences were found between men's and women's performance, as well as between each type of jump within each gender. A mixed-model analysis of variance detected gender differences with respect to changes in the jumping movement. For both sexes the jumps in order from worst to best were SNA, CMNA, SA, and CMA. Peak power values for men were 4,057, 4,020, 4,644, and 4,747 W, respectively, for the 4 jumps. The female power values were 2,543, 2,445, 2,842, and 2,788 W, respectively, for the 4 jumps. Arms increased jump height more than a counter movement for both genders, with jump heights for men at 29.6, 31, 36, and 38 cm, respectively, and those of women 21, 22, 26, and 27 cm, respectively. Use of the arms was found to increase the jump height of the men significantly more than that of women. Changes in jumping movements affect men and women differently. The greater increase in jump height for the men when using the arm swing could be because of greater upper body strength of men compared with women. This could have applications to training and upper body strength and also to modeling of jumping movements.     

Standard anthropometric, body composition, and strength variables as predictors of jumping performance in elite junior athletes

The aim of the study was to investigate whether variables routinely assessed while testing athletes can also predict movement performance. The relation between jumping performance and standard strength, anthropometric, and body composition variables was examined in elite junior basketball players. The 33 males were tested for maximal vertical jump, as well as for maximal isometric voluntary force and rate of force development of hip and knee extensors. Standard anthropometric and body composition measures (body height, lean body mass, as well as the percentage of fat and muscle tissue) were also taken. Except for maximal isometric forces (0.38 and 0.52 N.kg(-1) for hip and knee extensors, respectively), all correlation coefficients between the selected variables and jump height were insignificant. As a consequence, the corresponding multiple correlation coefficient, R = 0.71, also suggested a moderate predictability of jumping performance by the standard strength tests and anthropometric and body composition variables. The results obtained dispute the use of the examined tests in sport performance assessment, and also question applying the tests for other purposes such as evaluation of training procedures or selection of young athletes. Therefore, the results are in line with the concept that a reliable performance assessment in homogeneous groups of athletes requires predominantly movement-specific testing.     

Vertical jump, anaerobic power, and shooting accuracy are not altered 6 hours after strength training in collegiate women basketball players

We measured vertical jump, anaerobic power, and shooting accuracy in 18 Division I women basketball players (age 18-22 years) 6 hours following a morning strength training routine called a lift day (LD) and on a control day in which no strength training was performed. Subjects had been strength trained for 4 weeks prior to testing. The strength training session on lift day was a full-body workout and included 7 exercises performed in 3-6 sets at loads ranging from a 5 to 12 repetition maximum (RM). There were no significant differences in jump height with 2 legs (49.5 +/- 4.8 cm and 49.0 +/- 4.8 cm, LD and control, respectively), relative mean power output over 30 seconds on a Wingate bicycle test (6.4 +/- 0.8 W.kg(-1) and 6.6 +/- 0.7 W.kg(-1), LD and control, respectively), or shooting accuracy over 60 seconds (21.5 +/- 3.8 points/min and 21.3 +/- 4.1 points/min, LD and control, respectively). These data suggest that in collegiate women basketball players, a previous bout of strength training has no negative effect on vertical jump height, anaerobic power, or shooting accuracy.     

Sprint and vertical jump performances are not affected by six weeks of static hamstring stretching

The purpose of this study was to investigate whether 6 weeks of static hamstring stretching effects range of motion (ROM), sprint, and vertical jump performances in athletes. Twenty-one healthy division III women's track and field athletes participated in the study. Subjects were tested for bilateral knee ROM; 55-m sprint time; and vertical jump height before, at 3 weeks, and after the 6-week flexibility program. Subjects were randomly assigned to treatment and control groups and warmed up with a 10-minute jog on a track before a hamstring stretching protocol. The stretching protocol consisted of four repetitions held for 45 seconds, 4 days per week. Four variables (left and right leg ROM, 55-m sprint time, vertical jump) were analyzed using a repeated-measures analysis of variance design. No significant differences (P < or = 0.05) were found with any of the four variables between the stretching and control groups. Six weeks of a static hamstring stretching protocol did not improve knee ROM or sprint and vertical jump performances in women track and field athletes. The use of static stretching should be restricted to post practice or competition because of the detrimental effects reported throughout the literature. Based on the current investigation, it does not seem that chronic static stretching has a positive or negative impact on athletic performance. Thus, the efficacy of utilizing this practice is questionable and requires further investigation.     

Physiological and sport-specific skill response of olympic youth soccer athletes

Although many studies have been focused on soccer athletes, no comprehensive studies have been conducted on adolescent soccer athletes in the United States. Therefore, the purpose of this study was to quantify the physiological and sport-specific skill characteristics of Olympic Developmental Program (ODP) soccer athletes by age group and game experience. Following written, informed consent, 59 male athletes (age = 14.6 +/- 2.0 years; wt = 60.5 +/- 1.4 kg; ht = 172.4 +/- 1.2 cm) completed a battery of tests to determine aerobic power (VO(2)max), heart rate (HR(max)), ventilation (VE(max)), respiratory exchange ratio (RER), anaerobic threshold (AT), blood pressure (BP(rest/max)), anaerobic power/capacity [peak power (PP), mean power (MP), total work output (TWO), fatigue index (FI)], leg power [vertical squat jump (VJS), countermovement jump (VJC)], body composition [percent body fat (%BF), lean body mass (LBM)], joint range of motion (trunk, back, hip, knee, and ankle), and agility/sport-specific skills (T-test, line drill test, juggling test, Johnson wall volley, and modified-Zelenka circuit). Factor analyses with subsequent multivariate analyses of variance (MANOVAs) indicated significant main effects across age (p = 0.0001) but not by game experience (p = 0.82). Older athletes exhibited greater height, weight, LBM, VE(max), Time(max), PP, TWO, and VSJ values than younger athletes. Although not significant, there were differences with increasing age in the agility tests (T-test, wall volley, and juggling test). In conclusion, improvements in anaerobic power, agility, and sport-specific skill should be addressed at this developmental level of competition.     

Effects of electromyostimulation training on muscle strength and power of elite rugby players

The present study investigated the influence of a 12-week electromyostimulation (EMS) training program performed by elite rugby players. Twenty-five rugby players participated in the study, 15 in an electrostimulated group and the remaining 10 in a control group. EMS was conducted on the knee extensor, plantar flexor, and gluteus muscles. During the first 6 weeks, training sessions were carried out 3 times a week and during the last 6 weeks, once a week. Isokinetic torque of the knee extensors was determined at different eccentric and concentric angular velocities ranging from -120 to 360 degrees .s(-1). Scrummaging and full squat strength, vertical jump height and sprint-running times were also evaluated. After the first 6 weeks of EMS, only the squat strength was significantly improved (+8.3 +/- 6.5%; p < 0.01). After the 12th week, the -120 degrees .s(-1) maximal eccentric, 120 and 240 degrees .s(-1) maximal concentric torque (p < 0.05), squat strength (+15.0 +/- 8.0%; p < 0.001), squat jump (+10.0 +/- 9.5%; p < 0.01), and drop jump from a 40-cm height (+6.6 +/- 6.1%; p < 0.05) were significantly improved. No significant change was observed for the control group. A 12-week EMS training program demonstrated beneficial effects on muscle strength and power in elite rugby players on particular tests. However, rugby skills such as scrummaging and sprinting were not enhanced.     

Effects of velocity-specific training on rate of velocity development, peak torque, and performance

Little is known about the velocity-specific adaptations to training utilizing movement velocities in excess of 300 degrees x s(-1). The purpose of this investigation was to determine the effects of 4 weeks of slow (60 degrees x s(-1)) vs. fast (400 degrees x s(-1)) velocity training on rate of velocity development (RVD), peak torque (PT), and performance. Twenty male kinesiology students (22.0 years +/- 2.72; 178.6 cm +/- 7.1; 82.7 kg +/- 15.5) were tested, before and after 4 weeks of training, for PT production, RVD (at 60, 180, 300, 400, and 450 degrees x s(-1)), standing long jump (SLJ) distance, and 15- and 40-m sprint times. All participants underwent 8 training sessions, performing 5 sets of 5 repetitions of simultaneous, bilateral, concentric knee extension exercises on a Biodex System 3 isokinetic dynamometer at either 60 degrees or 400 degrees per second. Two 5 (speed) x 2 (time) x 2 (group) multivariate repeated measures analyses of variance revealed no significant differences between groups on any measure. Therefore, the groups were collapsed for analysis. There was a significant (p < 0.05) main effect for RVD by time and SLJ distance by time (pre- 227.1 cm +/- 21.2; post- 232.9 cm +/- 20.7) but no significant change in PT or 15- or 40-m sprint times. These results offer support for the suggestion that there is a significant neural adaptation to short-term isokinetic training performed by recreationally trained males, producing changes in limb acceleration and performance with little or no change in strength. Because results were independent of training velocity, it appears as though the intention to move quickly is sufficient stimulus to achieve improvements in limb RVD. Changes in SLJ distance suggest that open kinetic chain training may benefit the performance of a closed kinetic chain activity when movement pattern specificity is optimized.     

Changes evaluated in soccer-specific power endurance either with or without a 10-week,in-season,intermittent, high-intensity training protocol

The purpose of this study was to evaluate changes in soccer-specific power endurance of 34 female high school soccer players throughout a season either with or without an intermittent, high-intensity exercise protocol. Thirty-four female high school soccer players were tested prior to the 2000 fall season and again 10 weeks later. The tests included an abridged 45-minute shuttle test (LIST), hydrostatic weighing, vertical jump, 20-m running-start sprint, and 30-second Wingate test. The experimental group (EG; n = 17, age 16.5 +/- 0.9 years) completed a 10-week in-season plyometric, resistive training, and high-intensity anaerobic program. The control group (n = 17, age 16.3 +/- 1.4 years) completed only traditional aerobic soccer conditioning. Statistical significance was set at alpha < 0.05. The experimental group showed significant improvements in the LIST (EG = delta 394 seconds +/- 124 seconds), 20-m sprint (EG = Delta-0.10 seconds +/- 0.10 seconds), increase in fat-free mass (EG = delta 1.14 kg +/- 1.22 kg), and decreases in fat mass (EG = Delta-1.40 kg +/- 1.47 kg) comparing pre- to postseason. This study indicates that a strength and plyometric program improved power endurance and speed over aerobic training only. Soccer-specific power endurance training may improve match performance and decrease fatigue in young female soccer players.