Maximal Vertical Jumps Research Articles

Effect Of Weighted Jump Warm-Up On Vertical Jump In Division II Female Volleyball Players

Dynamic warm-up strategies are designed to positively impact performance. Research suggests that warm-ups which elicit a post activation potentiation (PAP) effect via high intensity muscular contractions may increase performance in subsequent activities requiring strength and power. The purpose of this investigation was to determine if a functional, dynamic, volleyball specific warm-up that included weighted jumps would elicit a PAP effect and increase subsequent vertical jump height. Ten trained female Division II volleyball players participated (age = 19.8 + 1.8 yrs; mass = 71.7 + 9.7 kg; ht = 167.8 + 23.9 cm). Subjects were at week 6 of their off-season conditioning program. Besides volleyball specific strength and conditioning, per NCAA guidelines, each player accumulates 2 hrs/wk of individual volleyball practice during this time period. Two different warm-up conditions lasting ∼ 5-7 minutes were individually employed at two different training sessions within one week. The first warm-up condition consisted of a functional, dynamic warm-up of light jogging, high knees, carioca, shuffling, ankle pops (all at 3 sets at 20 yds ea.), pogos (2 × 15 sec.), and tuck jumps (1 × 15 sec.). The second warm-up condition was identical to the first, except for the addition of 1 × 10 maximal vertical jumps with countermovement while wearing a weight vest loaded with 20% of their individual bodyweight. Starting at 4-minutes post warm-up in each condition, maximal vertical jump was assessed in two conditions: 1) 2-hand standing block vertical jump (SBVJ), and 2) 1-hand 3-step approach vertical jump (AVJ). Three trials per each condition were given, with 15 sec. rest intervals allowed between trials. The highest point touched on a vertical jump tester was recorded for each trial. The average of the three trials was used for data analysis. Paired Samples T-test was used to determine if there was a significant difference (p < 0.05) in vertical jump height (i.e., height touched) between the two conditions. The results of this study were mixed. No significant difference (p > 0.05) occurred in vertical jump height in the SBVJ condition between the two different warm-ups (262.1 vs. 263.0 cm, warm-up vs. warm-up with weight vest, respectively). However, the AVJ was significantly higher by 2.7 cm (p < 0.05; 275.1 vs. 277.8 cm) after the subjects added the weight vest to their warm-up routine. This study demonstrates that a functional, dynamic warm-up with the addition of weight jumps for 1 × 10 at 20% of bodyweight increases 3-step approach vertical jump ability in female collegiate volleyball players. However, no effect was seen in 2-hand standing block vertical jump ability. This may possibly be explained by the difference in the forces and energy involved during the stretch-shortening cycle in a 3-step approach vertical jump vs. a stationary standing block vertical jump. The coach may consider using a functional, dynamic, athletic warm-up that includes jumps with resistance to optimize performance in sports like volleyball where vertical jumps with an approach are key components of competition.

Development of lower limb stiffness and its contribution to maximum vertical jumping power during adolescence

Maximum power production during multi-joint tasks increases as children grow older. Previous research suggests that in adults, maximum power production in jumping is related to lower limb stiffness. In a developmental context, the question arises as to whether the relationship between maximum power production and lower limb stiffness is age-dependent. The purpose of this study was to investigate the relationship between lower limb stiffness and peak power production in adolescents (AD) and pre-adolescents (PA). With institutional approval, two groups of pre-adults (pre-adolescents: 11-13 years of age, N=43; adolescents: 16-18 years of age, N=30) performed 30 two-legged hops at their preferred frequency and three maximum counter-movement jumps. AD produced significantly greater peak power during the counter-movement jump than PA (t(71)=-5.28, P<0.001) even when body mass was accounted for. Lower limb stiffness was significantly correlated with peak power production during the counter-movement jump in AD (R=0.62, P<0.001) but not in PA (R=0.26, P=0.10). When normalised to body mass, the relationship between lower limb stiffness and peak power also differed between the two age groups (R=0.30, P=0.11 for AD and R=0.02, P=0.88 for PA). In addition, we found that during hopping, both PA and AD behaved like a simple spring-mass system. Our findings highlight the importance of lower limb stiffness in the context of muscular power production during multi-joint tasks. They let us speculate that during adolescence, children acquire the ability to take greater advantage of elastic energy storage in the musculotendinous system when performing maximum counter-movement jumps.

최대 수직 점프시 개인내 우수 수행과 비우수 수행의 역학적 비교

본 연구의 목적은 최대 수직점프시 개인내에서 발생하는 수행력의 차이와 이와 관련된 역학적 변인들의 영향을 규명하는데 있다. 이를 위해 20대 남성 20명을 대상으로 6회의 최대 수직점프를 실시하였으며, 이 가운데 최고 수행과 최저 수행을 추출한 후 수행력과 역학적 변인들을 비교, 분석하였다. 분석 결과, 우수수행과 비우수수행사이의 점프 높이는 약 4cm로 10% 정도의 유의한 차이를 보였으며 이는 이지시 중심의 높이(25%)와 이지속도(75%)에 기인하였다. 무릎관절과 엉덩관절의 역학적 출력은 유의한 차이가 나타나지 않은 반면 발목관절에서는 최대신전모멘트, 최대파워, 일량이 우수수행에서 유의하게 높았다. 최대수직점프에서 개인내 수행차는 주로 발목관절의 운동에 주로 기인한다고 할 수 있으며, 무릎과 엉덩관절의 역학적 출력은 수행력에 주요한 기여를 하지만 개인내 변이가 크지 않아 개인내 수행차에는 영향을 미치지 못하였다. 이에 비추어 점프력을 극대화하기 위해서는 트레이닝의 과정에서 발목관절의 역학적 출력을 증가시킬 수 있는 방안에도 보다 관심을 두어야 할 것으로 사료된다. The purpose of this study was to find differences of jumping performances within individual and to identify the influencing factors in these differences. 20 male subjects performed 6 maximal vertical jumps. The best(GP) & worst(BP) performance of each subject based on their jump height were compared in further analysis. There was a significant difference of approx. 10% in the jump height between GP and BP, which resulted from height of COM and vertical velocity at the instant of take-off. We could observe a significantly higher ankle moment in the GB more than the BP but no significant differences for the knee and hip joint. Also the maximum power of ankle joints in the GP were significantly higher than that in the BP. According to the results, the mechanical output of knee and hip joint are not as influential as that of ankle joint for difference of performance within individual. In conclusion, the results showed that mechanical output of the ankle joint could be more influential factors on the performances within individual although the knee and hip joint play an important role in the vertical jump. We therefore propose that more emphasis should be placed on the potentiation of the ankle joint for the training of the maximum vertical jump.

A Gender Comparison of Lower Extremity Landing Biomechanics Utilizing Different Tasks

Jump landings are routinely used to study gender differences in landing. Standardizing the jump height to a fixed vertical distance may bias results as women are forced to land from heights that are a greater percentage of their own maximum vertical jump (MVJ). PURPOSE: To compare lower extremity mechanics between genders from a fixed height and from a self initiated jump. METHODS: Nine male (21.50±1.20 years, 173.25±2.82cm, 75.58±7.92kg, 60.97±5.81cm MVJ) and 8 female (20.56±1.24 years, 161.11±6.01cm, 57.58±11.65kg, 33.13±9.76cm MVJ) subjects participated in this study. Subjects were given standard footwear. Maximum vertical jump heights were obtained. Subjects performed 6 successful trials of a drop landing (DL) from a 61cm height and a self initiated vertical jump landing (VJ) at their 80% MVJ height in random order. A 6-camera, EVa 3-D motion capture system (Motion Analysis, Santa Rosa, CA) captured (120 Hz) and analyzed (EVa version 5.11 and KinTrak 6.0 software) dominant lower extremity joint kinematics based on an 11 marker, 3 segment (thigh, shank, foot) model. Joint centers for the hip, knee and ankle were created according to Euler angle calculations. A synchronized force plate (AMTI, Watertown, MA) recorded time of initial contact and maximal vertical force. Dependent variables included: knee flexion angles at initial contact (KFIC), at maximal vertical ground reaction force, (KFMZ) and maximum knee flexion angle (MaxKF). Data were exported into spreadsheet and means for all trials in both conditions were created and imported to SPSS 13.0. Two 1-way ANOVAs tested for differences (P = 0.05) between groups in each condition. RESULTS: No significant differences were found between males and females for KFIC or KFMZ in either the VJ or DL. No significant difference was found in MaxKF between males (75.55± 8.46) and females (67.52± 6.31) in the DL. However, males had greater MaxKF angles (83.38± 18.90) than females in the VJ (66.22±15.01) (P=.001). CONCLUSIONS: Contrary to other published reports, our results showed no difference in knee flexion angles between genders in a DL task. Males exhibited greater absolute knee flexion in the VJ, which is not surprising given their MVJ heights. Future research investigating lower extremity motion during landing should incorporate appropriately comparable tasks.

Surface Electromyographic Assessment of the Effect of Dynamic Activity and Dynamic Activity with Static Stretching of the Gastrocnemius on Vertical Jump Performance

The purpose of this study was to investigate the effects of dynamic activity and dynamic activity/static stretching of the gastrocnemius muscle on vertical jump (VJ) performance. Additionally, muscle activity was recorded using electromyography. Thirteen healthy adults (7 men and 6 women) with a mean age of 26 +/- 4 years served as subjects. The average jump height and muscle activity from 3 separate maximal VJ attempts were performed at the start of each session to be used as baseline measures using the Kistler force plate and the Noraxon telemetry EMG unit. Subjects then performed 1 of 2 protocols: dynamic activity only or dynamic activity with static stretching. Each protocol was followed by 3 maximal VJ trials. Average VJ height was analyzed using a 2 (time: pre, post) x 2 (prejump protocol: dynamic activity, dynamic activity + stretching) analysis of variance with repeated measures on both factors. A paired-samples t-test was used to compare the intraday difference scores for EMG activity between the 2 conditions. Jump height was not influenced by the interaction of pre-post and protocol (p = 0.0146. There was no difference for the main effects of time (p = 0.274) and pre-jump protocol (p = 0.595). Gastrocnemius muscle activity was likewise not different for the 2 prejump protocols (p = 0.413). The results from this study imply that the use of static stretching in combination with dynamic activity of the gastrocnemius muscle does not appear to have an adverse affect on VJ height performance. The practical importance concerns the warm-up routine that coaches and athletes employ; that is, they may want to consider including an aerobic component when statically stretching the gastrocnemius immediately prior to a vertical jumping event.

Rehabilitation for Chronic Ankle Instability Does Not Influence Post-Impact Kinematics During a Dynamic Landing Task

PURPOSE: To compare the influence of two rehabilitation protocols on lower extremity kinematics after landing in subjects with chronic ankle instability (CAI). METHODS: Twenty-nine physically active subjects (10 males, 19 females; age: 20.24±2.11 yr; height: 174.26±8.29 cm; mass: 75.91±11.46 kg) with unilateral CAI reported to the laboratory for two testing sessions 6 weeks apart during which they performed a single-limb jump landing task using the injured and non-injured limb. Subjects jumped off two feet to a height equal to 50% of maximum vertical jumping height and landed onto a forceplate using one limb. Subjects were asked to land on the designated limb, stabilize as quickly as possible in a single-limb stance, and remain as motionless as possible for 5 seconds. Five jump-landings were performed on each test limb. During the task, hip flexion, knee flexion and ankle plantar flexion were captured with an electromagnetic tracking device. The subjects were randomly assigned to one of three groups: Ankle Rehabilitation (AR), Knee Rehabilitation (KR) or Control (NR). During the 6 weeks between the pre- and post-testing sessions, subjects in the AR and KR groups reported to the laboratory three times/week for supervised rehabilitation sessions designed to target function of the ankle (AR) or the knee (KR). Subjects in the NR group did not participate in any rehabilitation program during the six week period. All subjects reported to the lab at the end of the 6-week period and repeated the jumplanding procedures as performed in the pre-testing session. The peak kinematic values for hip flexion, knee flexion and ankle plantar flexion during the post-ground impact phase of the task served as the dependant variables. For each dependant variable, a separate Time by Limb by Group repeated measures ANOVA was performed. RESULTS: There were no significant interactions for hip flexion (F1,27=0.52, p=.60), knee flexion (F1,27=0.03, p=0.98) or ankle dorsiflexion (F1,27=3.09, p=.063). Additionally, there were no significant main effects among any of the variables. CONCLUSIONS: Rehabilitation designed for the ankle and knee did not influence kinematics of the ankle, knee and hip while stabilizing from a jump in subjects with CAI. It is possible that the selected variables may not be sensitive to the influence of rehabilitation.

Positive and Negative Loading and Mechanical Output in Maximum Vertical Jumping

The aim of this study was to evaluate the effect of external loading on mechanics of vertical jumping. We hypothesized that the muscular mechanical output could be higher under no-load conditions than in the presence of either positive or negative external loads. Fifteen physically active men performed maximal countermovement jumps (CMJ) on a force plate while a pulley system provided approximately constant vertical force acting in a way to either reduce or increase the body weight. As a result, the weight of the body approximately corresponded to the gravity acceleration from 0.70 to 1.30 g (g = 9.81 m.s(-2)). Regarding the jumping kinematics, we observed a significant (P < 0.001) load-associated decrease in both the peak velocity and lowering of the center of mass during the eccentric jump phase, but not in the duration of the subsequent concentric jump phase. Regarding the muscular mechanical output, both the mean power (P ) and peak momentum (M) revealed significant (P < 0.001) changes associated with loading, and further post hoc analyses revealed significantly higher values (P < 0.05-0.001) of both P and M for 1.00 g compared with most of the other loading conditions applied. The results suggest that subject's own body provides the optimal load for producing maximum mechanical output in vertical jumping. If corroborated by the results of future studies performed on other rapid movement, our findings could support the hypothesis that the muscular system is designed for producing maximum mechanical output in rapid movements when loaded only with the weight and inertia of its own body.

Coordination Specificity in Strength and Power Training

In this study, we tested the hypothesis that specificity of inter-joint coordination in power training improves training effects. We compared two different training regimes, one with and one without the possibility to exploit the coordination between knee and ankle, on performance and coordination in maximal vertical jumping and explosive squat movements. 22 subjects were divided into two groups for a 5-week training study. One group (Tsingle) trained squats (SQ) and plantar flexions (PL) in separate activities and the other group (Tmulti) trained squats ending with plantar flexion in one movement (SQPL), three times a week. Both groups increased their peak power during training movements between 2 - 15 % (depending on the training movement) but there were no group effects. There were no effects on vertical jumping performance. However, our data indicate different coordinative changes between groups in the vertical jump after the training period. The group specific training movements resulted in an increased power potential that is shown in the training movements themselves but did not transfer to an increased vertical jump performance in either group. However, some training movement specific coordination effects were seen during vertical jumping. In this study, these coordinative changes are specific to the training groups and may be a forerunner to improvements in vertical jumping.

Effects of a Short Duration Jump Training Program on Collegiate and Recreational Female Athletes

Females who participate in sports that involve jumping and cutting are four to six times more likely to suffer a serious knee injury than their male counterparts. PUrPose: This preliminary study investigated the effectiveness of a low-impact jump-training program on peak ground reaction forces (GRF), as well as jump height, landing velocity, and landing impulse for both collegiate and recreational athletes. It was hypothesized that the jump heights would increase for the trained groups while the GRF values would decrease after the intervention. METHODS: Female collegiate soccer players (SOC) and recreational athletes (REC) were recruited and placed into either a control (C) ((n=3, SOC C 19.4+1.5 yrs; n=3, REC C 22.2+1.1 yrs)) or training (T) (n=5, SOC T 18.6+.9 yrs; n=5 REC T 21+.6) group. Participants in the training groups completed 12 training sessions (4 weeks at 3X per week). Ground reaction forces (GRF) were measured with a 600 Hz Bertec force plate before and after a jump training intervention for the training group and at the beginning and end of the 12 week time period for the control groups. Each subject completed 3 maximum vertical jumps during both pre and post testing sessions and the highest jump was used in the analysis since they were instructed to perform a maximal vertical jump. RESULTS: A 4X2 (group × time) repeated measures ANOVA indicated a significant interaction (p < 0.05) for jump height, landing velocity andjump time. Follow up of the data indicated the training increased jump height and decreased peak landing forces for the REC T athletes, while the SOC T group only decreased their peak landing forces, but increased their jump velocity. There were no changes observed in the control groups for GRF, and the jump heights decreased. CONCLUSIONS: Decreases were observed in GRF for both trained groups; however, changes were larger for the REC T group. Data suggest that a jump training program may increase jump height while reducing ground reaction forces in female athletes. These improvement trends should increase with a longer jump training program.Table

Changes in Physical and Morphological Profiles in Argentine Elite Volleyball Male Players during the Competition

PURPOSE: To examine changes in morphological and physical fitness profiles of elite male volleyball players in a competitive season. METHODS: Ten members of an Argentine elite male volleyball team (age: 28.5 ±6.1 yrs, height: 188.2 ± 9.8 cm.) were studied during a competition phase consisting of a period for 10 weeks. The entire season was characterized by 4–6 weekly sessions for playing drills, 1–2 weekly competitive games and by 2–3 weekly sessions for physical conditioning mostly for strength and explosive strength training. Body weight (BW), body composition (body fat mass (BFM), body muscular mass (BMM)), maximal oxygen consumption (VO2max, from yo-yo test), maximal force testing (from 3 repetitions in squats (SQ) and bench press (BP)) and maximal jumping height (squat jump (SJ), counter movement jump (CMJ), Abalakov jump (ABJ)) were assessed in two periods: prior and post competitive season. RESULTS: The present findings showed that the competitive phase in subjects led to no changes in BW (from 91 ±11 to 90.4 ± 9.2 kg.), BFM (from 11.5 ± 5.1 to 11.7 ±3.2 kg.) and BMM (from 50.5 ± 3.6 to 50.8 ± 2.5 kg), but a significant (p <0.05) increase took place in VO2max (from 44 ± 4 to 51 ±3.5 ml.kg.min.). Significant changes (p <0.05) were observed in SQ (from 97.1 ± 22.3 to 112.5 ± 36.5 kg.), BP (from 66.7 ± 13.9 to 80.8 ± 10.6 kg.) as well as in the maximal vertical jumping heights: SJ (from 44.7 ± 3.4 to 47.3 ± 4.4 cm.), CMJ (from 47.3 ± 4.4 to 49.8 ± 3.3 cm.) and ABJ (from 53.7 ±5.8 to 57.9 ±5.7 cm.). CONCLUSIONS: Aerobic conditioning appears to be essential in volleyball players for rigorous training and elite competition in what is predominantly a power sport. Maximal strength and explosive strength are valuable physiological ingredients of the physical conditioning program during a competitive season: gains in maximal strength lead to enhance power, which could in turn be applied during competition by skill performances like more effective spiking or blocking due to more explosive jumping and higher reach. Significant changes in aerobic and strength capacities can be achieved without gaining or loosing BW, BFM or BMM.

Effect of low‐repetition jump training on bone mineral density in young women

The hypothesis of the present study was that low‐repetition and high‐impact training of 10 maximum vertical jumps/day, 3 times/week would be effective for improving bone mineral density (BMD) in ordinary young women. Thirty‐six female college students, with mean age, height, and weight of 20.7±0.7 years, 158.9±4.6 cm, and 50.4±5.5 kg, respectively, were randomly divided into two groups: jump training and a control group. After 6 months of maximum vertical jumping exercise intervention, BMD in the femoral neck region significantly increased in the jump group from the baseline (0.984±0.081 vs 1.010±0.080 mg/cm2; P&lt;0.01), although there was no significant change in the control group (0.985±0.0143 vs 0.974±0.134 mg/cm2). And also lumbar spine (L(2–4)) BMD significantly increased in the jump training group from the baseline (0.991±0.115 vs 1.015±0.113 mg/cm2; P&lt;0.01), whereas no significant change was observed in the control group (1.007±0.113 vs 1.013±0.110 mg/cm2). No significant interactions were observed at other measurement sites, Ward's triangle, greater trochanter, and total hip BMD. Calcium intakes and accelometry‐determined physical daily activity showed no significant difference between the two groups. From the results of the present study, low‐repetition and high‐impact jumps enhanced BMD at the specific bone sites in young women who had almost reached the age of peak bone mass.

The energetics and benefit of an arm swing in submaximal and maximal vertical jump performance

The aims of this study were to investigate the energy build-up and dissipation mechanisms associated with using an arm swing in submaximal and maximal vertical jumping and to establish the energy benefit of this arm swing. Twenty adult males were asked to perform a series of submaximal and maximal vertical jumps while using an arm swing. Force, motion and electromyographic data were recorded during each performance and used to compute a range of kinematic and kinetic variables, including ankle, knee, hip, shoulder and elbow joint powers and work done. It was found that the energy benefit of using an arm swing appears to be closely related to the maximum kinetic energy of the arms during their downswing, and increases as jump height increases. As jump height increases, energy in the arms is built up by a greater range of motion at the shoulder and greater effort of the shoulder and elbow muscles but, as jump height approaches maximum, these sources are supplemented by energy supplied by the trunk due to its earlier extension in the movement. The kinetic energy developed by the arms is used to increase their potential energy at take-off but also to store and return energy from the lower limbs and to “pull” on the rest of the body. These latter two mechanisms become more important as jump height increases with the pull being the more important of the two. We conclude that an arm swing contributes to jump performance in submaximal as well as maximal jumping but the energy generation and dissipation sources change as performance approaches maximum.

Effects of isometric squat training on the tendon stiffness and jump performance

The present study aimed to investigate the effect of isometric squat training on human tendon stiffness and jump performances. Eight subjects completed 12 weeks (4 days/week) of isometric squat training, which consisted of bilateral leg extension at 70% of maximum voluntary contraction (MVC) for 15 s per set (10 sets/day). Before and after training, the elongations of the tendon-aponeurosis complex in the vastus lateralis muscle and patella tendon were directly measured using ultrasonography while the subjects performed ramp isometric knee extension up to MVC. The relationship between the estimated muscle force and tendon elongation was fitted to a linear regression, the slope of which was defined as stiffness. In addition, performances in two kinds of maximal vertical jumps, i.e. squatting (SJ) and counter-movement jumps (CMJ), were measured. The training significantly increased the volume (P < 0.01) and MVC torque (P < 0.01) of the quadriceps femoris muscle. The stiffness of the tendon-aponeurosis complex increased significantly from 51 +/- 22 (mean +/- SD) to 59 +/- 24 N/mm (P = 0.04), although that of the patella tendon did not change (P = 0.48). The SJ height increased significantly after training (P = 0.03), although the CMJ height did not (P = 0.45). In addition, the relative difference in jump height between SJ and CMJ decreased significantly after training (P = 0.02). These results suggest that isometric squat training changes the stiffness of human tendon-aponeurosis complex in knee extensors to act negatively on the effects of pre-stretch during stretch-shortening cycle exercises.

Effect of low-repetition jump training on bone mineral density in young women

The hypothesis of the present study was that low-repetition and high-impact training of 10 maximum vertical jumps/day, 3 times/wk would be effective for improving bone mineral density (BMD) in ordinary young women. Thirty-six female college students, with mean age, height, and weight of 20.7+/-0.7 yr, 158.9+/-4.6 cm, and 50.4+/-5.5 kg, respectively, were randomly divided into two groups: jump training and a control group. After the 6 mo of maximum vertical jumping exercise intervention, BMD in the femoral neck region significantly increased in the jump group from the baseline (0.984+/-0.081 vs. 1.010+/-0.080 mg/cm2; P<0.01), although there was no significant change in the control group (0.985+/-0.0143 vs. 0.974+/-0.134 mg/cm2). And also lumbar spine (L2-4) BMD significantly increased in the jump training group from the baseline (0.991+/-0.115 vs. 1.015+/-0.113 mg/cm2; P<0.01), whereas no significant change was observed in the control group (1.007+/-0.113 vs. 1.013+/-0.110 mg/cm2). No significant interactions were observed at other measurement sites, Ward's triangle, greater trochanter, and total hip BMD. Calcium intakes and accelometry-determined physical daily activity showed no significant difference between the two groups. From the results of the present study, low-repetition and high-impact jumps enhanced BMD at the specific bone sites in young women who had almost reached the age of peak bone mass.

Effects of adding a preceding run-up on performance, blood lactate concentration and heart rate during maximal intermittent vertical jumping

In this study, we examined the effects of a prior run-up on intermittent maximal vertical jump performance. Seven regionally ranked male volleyball players volunteered to participate in the study. They performed three randomized tests: (1) six repeated intermittent maximal jumps (jump condition), (2) six repeated intermittent run-ups (run-up condition), and (3) six repeated run-ups followed by maximal jumps (run-up plus jump condition). All performances were assessed and blood lactate concentration and heart rate were measured before and after each of the tests. Mean ( ± ) jump performance (64.7 ± 2.3 cm) increased significantly (P = 0.02) over the course of the jump condition and was significantly higher (P < 0.001) than for the run-up plus jump condition (58.0 ± 3.2 cm), which tended to decrease with repetition. Blood lactate concentration was significantly higher in the run-up plus jump condition (3.73 ± 0.24 mmol · l−1) than in the jump (2.61 ± 0.26 mmol · l−1, P = 0.02) and run-up (2.86 ± 0.18 mmol · l−1, P = 0.03) conditions. The increase in heart rate was significantly higher both in the run-up plus jump condition (33 ± 6 beats · min−1, P = 0.05) and run-up condition (33 ± 4 beats · min−1, P = 0.02) than in the jump condition (21 ± 3 beats · min−1). The results indicate that the addition of run-ups probably impeded performance in the repetition of vertical jumps.

Scaling of muscle power to body size: the effect of stretch-shortening cycle

The present study investigates the relationship between muscle power recorded in vertical jumps and body size, and explores possible differences in this relationship between the concentric (CON) and stretch-shortening cycle (SSC) muscle action. Physical education students (N = 159) were tested with the performance of various CON and SSC maximum vertical jumps. The relationship between muscle power (P) and body size (S) was assessed by P=aS(b) where a and b were the constant multiplayer and scaling exponent, respectively. With respect to body mass and fat-free mass, the scaling exponents b for mean muscle power (calculated from the ground reaction force) in CON and SSC jumps were within the range 0.69-0.82 and 0.90-1.15, respectively. With respect to body height, the scaling exponent was higher (0.76-0.97 and 1.23-1.79, respectively), but the observed relationship proved to be relatively weak. However, when jump height was used as an index of muscle power, the same exponents were close to zero (suggesting no relationship with any of the indices of body size) in all the jumps except an SSC based hopping jump that demonstrated a weak but positive relation to body size. In conclusion, muscle power could scale to body size at a higher rate than predicted by geometric similarity (i.e. b = 0.67), while larger individuals could gain more when switching from CON to SSC muscle action. These findings could be based on a non-geometric scaling of transversal with respect to longitudinal dimensions and/or on different scaling rates of muscles and tendons.

Functional Stability During Jumps And Jump Landings

The notion that lower extremity function is symmetrical is common in the scienfitic literature. In addition, health care professionals often use the uninjured lower extremity as a benchmark for the injured limb during rehabilitation. However, the unilateral nature of injuries may indicate that the assumption of functional symmetry may be false. In addition, differences in injury rates between males and females dictates the need for a gender comparison. PURPOSE To evaluate ground reaction forces and measures of dynamic stability for right and left legs during drop landings and countermovement jumps and subsequent landings. METHODS Eleven healthy males females (age: 22.3±4.0 y, 180.3±7.3 cm, 78.4±9.3kg) and10 healthy females (age: 21.1±1.2 y, 164.6±5.3 cm, 61.0±5.6kg) with no history of lower extremity injury or vestibular disorders participated. Subjects performed two drop jumps from a height of 40cm and two maximum vertical jumps (in random order). Each activity concluded by executing two-footed landings with each foot striking separate force plates (200 Hz). During each landing, subjects were instructed to stabilize as quickly as possible, place their hands on their hips, and hold that position for three seconds. Maximum vertical ground reaction forces during each phase of the jumps and landings, as well as, times to stabilization during landings were calculated for right and left legs. RESULTS Separate two-way ANOVA (side × gender) revealed females took significantly longer to stabilize during drop landings than males [F(1,38)=11.676, p = .002] based on vertical ground reaction forces. More specifically, females required an additional 500ms to become stable. No main effects for side (p > 0.05). No interactions were detected (p > 0.05). CONCLUSION The results indicate that healthy individuals achieve stability with their right and left legs similarly while performing jump tasks. The increased time to stabilization required by females may help explain the increased rate of injury commonly observed in the athletic female population and provides justification for future studies involving dynamic stability and gender differences. Posters Displayed One and one-half hour author presentation times are staggered among authors from 9:30–11:00 a.m. and 11:00 a.m.–12:30 p.m.

Impact Attenuation And Kinetic Characteristics Of Cross Training Shoes In Landing And Jumping Activities

Very few footwear studies have examined athletic shoes designed for sports other than running. Cross-training footwear is designed to meet needs of a variety of sports and sport training environments with key features that include generating power for performance and attenuating impacts for injury prevention. PURPOSE To examine kinetic characteristics of impact attenuation in landing and power generation in jumping of four different cross training shoes. METHODS Ten healthy male recreational athletes (age:21.5±2.5 yrs) performed five step-off landing trials and five maximum vertical jumping trials in each of four cross-training shoes (from three leading footwear manufacturers). Right sagittal kinematic data (120 Hz), ground reaction forces (GRF,1200 Hz), and forehead and distal tibia accelerations (ACC, landing only) were measured simultaneously. The landing height was determined individually based upon potential energy of a “mid-size” person (80 kg) landing from a 0.6 m height. Material tests were performed on selected sizes of each shoe model.A one-way repeated measures ANOVA and post-hoc comparisons (p < 0.05) were performed on selected variables. RESULTS The results from the landing trials showed that Shoes A (23 N/kg) and B (26 N/kg) had significantly smaller forefoot peak GRF than Shoes C (29 N/kg) and D 28 N/kg). Shoes A (2274 N/kg/s) and B (2630 N/kg/s) also showed lower loading rate associated with the forefoot contact than Shoes C (3316 N/kg/s) and D (3336 N/kg/s). No significant changes were seen in ACC data. The jumping GRF results normalized to the individual jump height indicated significantly greater peak power for Shoes C (50 Wm/kg) and D (51 Wm/kg) compared to A (48 Wm/kg). Maximum peak GRF for Shoe D (16 Nm/kg) was greater than Shoe A (15 Nm/kg). In addition, kinematic data showed not clear trends in landing or jumping trials. The material testing indicated that Shoes A and B had the smallest forefoot stiffness values (9.2 and 9.6 N/mm) compared to Shoe C and D (18.0 and 12.7 N/mm) obtained in a fixibility test. Energy loss for Shoes A and B (41%and 43%) were greater than Shoes C and D (33 and 35%). CONCLUSIONS The results suggested that the Shoes A and B showed slightly better forefoot impact attenuation properties. Shoe D and C demonstrated better jumping performance than Shoe A. But better performance may come at a price of decreased cushioning.

Effect Of Rehydration And Carbohydrate Ingestion On Physical, Skilled And Cognitive Performance During Basketball

PURPOSE To investigate the effects of hydration and ingestion of a carbohydrateelectrolyte beverage on exercise performance during a simulated basketball “game”. METHODS A reproducible, high-intensity, “stop-and-go” exercise protocol (120 min including a 30-min warm-up and a 15-min half-time break) designed to closely mimic the physical demands of a competitive basketball game was utilized. Each “half” of the protocol included: 20 maximum vertical jumps, 20 maximum 15m sprints, 23 “defensive patterns” (70% VO2max), 56 3s “rests”, 15 25s “rests”, 15 “jogs” (2X20m @ 80% VO2max), and 5 “walks” (2X10m @ 40% VO2max). Twelve participants (6 men, 6 women) took part in 3 counterbalanced exercise sessions where a sports drink (6% carbohydrate-electrolyte, CHO), flavored placebo (PLA) or no fluid (CON) was provided. During CHO and PLA, participants ingested 20-ml fluid per kg body weight in portions of 2–5 ml/kg prior to and during exercise. Blood samples were taken and various performance measures were recorded prior to, during, and following exercise. RESULTS Blood glucose was higher in CHO compared to PLA & CON. Heart rate was greater in CON vs. CHO and PLA during the second “half” (172±2 bpm vs. 164±4 and 165±3 bpm, respectively). Participants lost more body water following CON compared to CHO and PLA as indicated by change in nude body weight following exercise (2.1±0.2 kg vs. 0.6±0.1 and 0.8±0.2 kg, respectively). Rating of perceived exertion (RPE) was lower in CHO (16.3±0.3) compared to CON (17.0±0.3) in the “4th quarter”. Time to perform a dribbling/lay-up task at the end of the “game” increased from CHO (167.9±2.6 s) to PLA (169.4±3.2 s) to CON (172.3±3.0, not significant; p=0.11). Blood lactate concentration, 15-m sprint time, vertical jump height, and body temperature were not different between trials. There was a trend for improvement in free throw accuracy and Stroop color-word score in CHO compared to PLA & CON (not significant) CONCLUSION Fluid and carbohydrate consumption reduced RPE, but had little effect on repetitive anaerobic performance during “basketball”. Further investigation is necessary to determine whether fluid and/or carbohydrate may affect skilled or cognitive tasks during basketball or other “stop-and-go” sports. Supported by the Gatorade Sports Science Institute.

Effect Of Rehydration And Carbohydrate Ingestion On Physical, Skilled And Cognitive Performance During Basketball

PURPOSE To investigate the effects of hydration and ingestion of a carbohydrateelectrolyte beverage on exercise performance during a simulated basketball “game”. METHODS A reproducible, high-intensity, “stop-and-go” exercise protocol (120 min including a 30-min warm-up and a 15-min half-time break) designed to closely mimic the physical demands of a competitive basketball game was utilized. Each “half” of the protocol included: 20 maximum vertical jumps, 20 maximum 15m sprints, 23 “defensive patterns” (70% VO2max), 56 3s “rests”, 15 25s “rests”, 15 “jogs” (2X20m @ 80% VO2max), and 5 “walks” (2X10m @ 40% VO2max). Twelve participants (6 men, 6 women) took part in 3 counterbalanced exercise sessions where a sports drink (6% carbohydrate-electrolyte, CHO), flavored placebo (PLA) or no fluid (CON) was provided. During CHO and PLA, participants ingested 20-ml fluid per kg body weight in portions of 2–5 ml/kg prior to and during exercise. Blood samples were taken and various performance measures were recorded prior to, during, and following exercise. RESULTS Blood glucose was higher in CHO compared to PLA & CON. Heart rate was greater in CON vs. CHO and PLA during the second “half” (172±2 bpm vs. 164±4 and 165±3 bpm, respectively). Participants lost more body water following CON compared to CHO and PLA as indicated by change in nude body weight following exercise (2.1±0.2 kg vs. 0.6±0.1 and 0.8±0.2 kg, respectively). Rating of perceived exertion (RPE) was lower in CHO (16.3±0.3) compared to CON (17.0±0.3) in the “4th quarter”. Time to perform a dribbling/lay-up task at the end of the “game” increased from CHO (167.9±2.6 s) to PLA (169.4±3.2 s) to CON (172.3±3.0, not significant; p=0.11). Blood lactate concentration, 15-m sprint time, vertical jump height, and body temperature were not different between trials. There was a trend for improvement in free throw accuracy and Stroop color-word score in CHO compared to PLA & CON (not significant) CONCLUSION Fluid and carbohydrate consumption reduced RPE, but had little effect on repetitive anaerobic performance during “basketball”. Further investigation is necessary to determine whether fluid and/or carbohydrate may affect skilled or cognitive tasks during basketball or other “stop-and-go” sports. Supported by the Gatorade Sports Science Institute.