Press Velocity Research Articles

The Impact of Exercise Order on Velocity Performance in the Bench Press and the Squat: A Comparative Study

We analyzed the influence of exercise order using the bench press and squat as the first or second exercise of the session on velocity performance. Ten male trained individuals (20.9 ± 0.7 years) randomly performed two protocols of three sets of six repetitions at 80% of their one-repetition maximum with different exercise sequences: the bench press followed by the squat (BP + S) and the squat followed by the bench press (S + BP). A linear velocity transducer attached to the Smith machine barbell measured the mean propulsive velocity (MPV), peak velocity (PV), and time to peak velocity. Additionally, blood lactate and heart rate were measured. Regarding the bench press, differences were found in the MPV in the first (BP + S: 0.50 ± 0.07 m·s−1 vs. S + BP: 0.42 ± 0.08 m·s−1; p = 0.03, g = 0.72) and second sets (0.50 ± 0.06 m·s−1 vs. 0.42 ± 0.07 m·s−1; p = 0.03, g = 0.73), and in the PV in the second set (0.74 ± 0.09 m·s−1 vs. 0.63 ± 0.09 m·s−1; p = 0.02, g = 0.86). Regarding the squat, although the S + BP sequence tended to show higher velocities, no significant differences were found between protocols. These results showed that squatting first decreased subsequent bench press velocity performance. On the other hand, squat velocity performance was not impaired when preceded by the bench press.

Changes in strength-related outcomes following velocity-monitored resistance training with 10 % and 20 % velocity loss in older adults

We compared the effects of velocity-monitored resistance training with an intra-set velocity loss (i.e., the decrement in repetition velocity over the set) of 10 % vs. 20 % on strength-related outcomes in older adults. We randomly assigned eighteen older adults to a velocity loss group of 10 % (n = 10; 78 ± 12 years) or 20 % (n = 8; 73 ± 10 years) to perform a 10-week training program. The primary outcomes were the one-repetition maximum (1RM) and the average mean velocity against absolute loads associated with loads <60 % 1RM (MVlow) and ≥ 60 % 1RM (MVhigh) in the leg and chest press exercises, assessed at pre-, mid- (week 5), and post-test. Secondary outcomes included handgrip strength, 1-kg medicine ball throw distance, 10-m walking time, and five-repetition sit-to-stand time. No differences between groups were found in any outcome at any time (p > 0.05). Both groups improved the 1RM leg press from pre- to mid- and post-test and the MVlow and MVhigh from pre- to mid-test (p < 0.05). No group improved the 1RM chest press (p > 0.05), but both increased the MVlow from pre- to mid-test (p < 0.05). Furthermore, both groups improved the sit-to-stand time, while only the 20 % velocity loss group significantly improved handgrip strength and 10-m walking time (p < 0.05). The results showed that both velocity losses improved leg press strength and velocity, chest press velocity, and sit-to-stand time in older adults, although a 10 % velocity loss was more efficient as it required less volume (i.e., total repetitions) than 20 %. Nevertheless, the latter seems required to optimize handgrip strength and 10-m walking time in older people.

Effects of Short-Term Golden Root Extract (Rhodiola rosea) Supplementation on Resistance Exercise Performance.

The purpose of this study was to examine the effects of short-term Golden Root Extract (GRE; Rhodiola rosea) supplementation on blood lactate, catecholamines, and performance during repeated bench press exercise. Resistance-trained males (n = 10) participated in this study. In a double-blinded, crossover, counterbalanced study design, participants supplemented with either 1500 mg/day of GRE or placebo (PL; gluten-free cornstarch) for 3 days prior to experimentation. An additional 500 mg dose was ingested 30 min prior to exercise testing. During each exercise trial, participants completed 2 repetitions of bench press at 75% of one-repetition maximum (1RM) as explosively as possible. A linear position transducer was used to measure mean concentric velocity. After 5 min of rest, participants completed 3 sets × repetitions to failure (RTF) at 75% 1RM separated by 2 min of rest between each set. A capillary blood sample was obtained pre- (PRE) and immediately post- (POST) exercise to measure blood concentrations lactate (LA), epinephrine (EPI), and norepinephrine (NE). Mean concentric velocity was significantly higher with GRE when compared to PL (p = 0.046). However, total RTF were significantly lower with GRE versus PL (p < 0.001). Regardless of treatment, LA was significantly higher Post versus Pre (p < 0.001), but GRE resulted in greater Post values compared to PL (p = 0.049). EPI and NE increased in both conditions Pre to Post (p < 0.001). However, Pre NE was significantly higher with GRE versus PL (p = 0.008). Findings indicate that short-term GRE supplementation increases mean bench press velocity but decreases bench press repetition volume. Furthermore, GRE resulted in higher NE levels and blood lactate following exercise. Thus, supplementing with GRE may enhance explosive resistance training performance but may also impair upper body strength-endurance.

Comparison of lift velocity and power output between barbell and dumbbell bench presses

Objectives: The purpose of this study was to assess differences in bench press velocity and power production with barbell and dumbbells. Design: Randomized cross-over design. Methods: College men (n = 20, age = 18-24 yrs) were measured for average and peak velocities and power during maximal effort single repetitions using barbell and bilateral dumbbells at loads equivalent to 30%, 50%, and 70% of body mass. Three repetitions were performed at each load with one-minute recovery between each repetition and 10 minutes between loads. During each repetition for each mode, average and peak velocity and power were monitored using a linear accelerometer. Results: Interclass correlation coefficients across the 3 trials for peak and average velocities were high for both barbell (ICC = 0.957 and 0.821, respectively) and dumbbells (ICC = 0.947 and 0.855, respectively). Peak power output was sig nificantly higher (p < 0.009) for barbell than dumbbells at 50% and 70% loads. Average power output was significantly different (p < 0.001) across the 3 loads but not significantly different between barbell and dumbbells (p = 0.35). Although velocity decreased as load increased, higher power outputs were produced across increases in loads. Peak power output was reached at 70% of body mass with barbell and 50% with dumbbells. Conclusion: Either barbell or bilateral dumbbell bench press exercises can be used to evaluate upper-body power with sim ilar effectiveness.

Potentiating Effects of Accentuated Eccentric Loading Are Dependent Upon Relative Strength.

Merrigan, JJ, Tufano, JJ, and Jones, MT. Potentiating effects of accentuated eccentric loading are dependent upon relative strength. J Strength Cond Res 35(5): 1208-1216, 2021-The purpose was to evaluate the acute effects of accentuated eccentric loading (AEL) on bench press velocity and subsequent perceived effort (ratings of perceived exertion [RPE]) and soreness. Resistance-trained men (n = 8) and women (n = 2) completed 4 sets of 5 bench press repetitions with AEL and traditional loading (TL) using concentric loads of 50% (AEL50, TL50) and 65% (AEL65, TL65) 1-repetition maximum (1RM). Throughout each TL set, the eccentric load remained identical to the concentric. Variable resistance during the first repetition of AEL equaled 120% 1RM. Hierarchical Linear Modeling was used to evaluate differences between AEL and TL (p < 0.05). For the first repetition, AEL50 and AEL65 resulted in slower eccentric and concentric velocities. The increasing slope of eccentric and concentric velocity across repetitions was greater during AEL50 and AEL65 compared with TL50 and TL65, respectively (p < 0.05). As an individual's strength increased, AEL50 resulted in slower eccentric velocity and faster concentric velocity than TL50. The AEL65 resulted in faster concentric velocity than TL65 (p < 0.05). Mean protocol comparisons revealed trivial to small effects between AEL and TL. There were no differences in RPE or soreness between protocols with soreness ratings remaining unchanged from baseline (1.80 ± 0.20 AU; p < 0.05). Overall, AEL was not effective for increasing concentric velocity during the bench press with current loading protocols. Yet, stronger individuals may exhibit increases in concentric velocity from AEL, which may be a result of different pacing strategies employed during the eccentric phase. Furthermore, when using the current AEL protocols, eccentric intensities were increased with no greater RPE or soreness.

Is the OUTPUT Sports Unit Reliable and Valid When Estimating Back Squat and Bench Press Concentric Velocity?

Merrigan, JJ and Martin, JR. Is the OUTPUT sports unit reliable and valid when estimating back squat and bench press concentric velocity? J Strength Cond Res 36(8): 2069-2076, 2022-This study evaluated the reliability and concurrent validity of the OUTPUT sports inertial unit to measure concentric velocity of free-weight back squat and bench press exercises. Eleven men and women performed back squat and bench press 1 repetition maximum (1RM) testing. One week later, subjects performed 3 repetitions of each exercise with 35, 45, 55, 65, 75, and 85% 1RM (18 total repetitions). The OUTPUT and 4 cable extension transducers (criterion) simultaneously recorded the mean and peak velocity. The OUTPUT had acceptable reliability for all loads except 85% 1RM for back squat and bench press (intraclass correlation coefficient = 0.72-0.96, coefficient of variation = 0.03-0.12). High systematic biases existed for the mean and peak velocity for the back squat and bench press, according to Bland-Altman plot's wide limits of agreement and ordinary least products regressions. According to Bland-Altman plots, OUTPUT tended to overestimate bench press velocity and overestimate back squat velocity at slower velocities. Least products regression analyses determined proportional bias existed for the mean and peak velocity of the back squat and peak velocity of the bench press. In conclusion, researchers and practitioners are advised not to compare velocity estimates of the OUTPUT unit with criterion devices because these methods cannot be used interchangeably. However, because of the demonstrated reliability when estimating the mean and peak velocity, strength and conditioning practitioners may find the OUTPUT unit valuable for monitoring performance of the back squat and bench press exercises. Yet, caution should be taken when evaluating loads ≥85% 1RM.

Bench Press Load-Velocity Profiles and Strength After Overload and Taper Microcyles in Male Powerlifters

Williams, TD, Esco, MR, Fedewa, MV, and Bishop, PA. Bench press load-velocity profiles and strength after overload and taper microcyles in male powerlifters. J Strength Cond Res 34(12): 3338-3345, 2020-The purpose of this study was to quantify the effect of an overload microcycle and taper on bench press velocity and to determine if the load-velocity relationship could accurately predict 1-repetition maximum (1RM). Twelve male powerlifters participated in resistance training structured into an introduction microcycle, overload microcycle (PostOL), and taper (PostTP). At the end of each microcycle, subjects completed a bench press for 1RM assessment consisting of warm-up sets at 40, 55, 70, and 85% of a previously established 1RM. The mean concentric velocity (MCV) was recorded during each warm-up set. A predicted 1RM (p1RM) was calculated using an individualized load-velocity profile (LVP). The average MCV decreased after PostOL (0.66 ± 0.07 m·s) compared with baseline (BL) (p = 0.003; 0.60 ± 0.11 m·s) but increased after PostTP (0.67 ± 0.09 m·s). One-repetition maximum increased from PostOL (146.7 ± 19.8 kg) to PostTP (p = 0.002; 156.1 ± 21.0 kg), with no differences observed between other test sessions (p > 0.05). Bland-Altman analysis indicated that p1RM was consistently higher than measured 1RM (3.4-7.8 kg), and the limits of agreement were extremely wide. However, very large to near perfect correlations (r = 0.89 to 0.96) were observed between p1RM and 1RM during BL, PostOL, and PostTP. The load-velocity relationship established from submaximal sets did not accurately predict 1RM, but MCV was affected by changes in weekly training loads. Velocity-based measurements seem to be more sensitive to changes in training loads than maximal strength.

Evidence for early arousal-based differentiation of emotions in children's musical production.

Accurate perception and production of emotional states is important for successful social interactions across the lifespan. Previous research has shown that when identifying emotion in faces, preschool children are more likely to confuse emotions that share valence, but differ in arousal (e.g. sadness and anger) than emotions that share arousal, but differ on valence (e.g. anger and joy). Here, we examined the influence of valence and arousal on children's production of emotion in music. Three-, 5- and 7-year-old children recruited from the greater Hamilton area (N=74) 'performed' music to produce emotions using a self-pacing paradigm, in which participants controlled the onset and offset of each chord in a musical sequence by repeatedly pressing and lifting the same key on a MIDI piano. Key press velocity controlled the loudness of each chord. Results showed that (a) differentiation of emotions by 5-year-old children was mainly driven by arousal of the target emotion, with differentiation based on both valence and arousal at 7years and (b) tempo and loudness were used to differentiate emotions earlier in development than articulation. The results indicate that the developmental trajectory of emotion understanding in music may differ from the developmental trajectory in other domains.

Effect of home‐based resistance training performed with or without a high‐speed component in adults with severe obesity

1) To evaluate the effects of walking and home‐based resistance training on function, strength, power, anthropometry and quality of life (QoL) in adults with severe obesity, and 2) to assess whether performing resistance exercises with maximal concentric velocity provides additional benefits compared with traditional slow‐speed resistance training. Methods Adults with a body mass index of ≥40 kg/m2 were randomised to slow‐speed strength training (ST; n = 19) or high‐speed power training (PT; n = 19). Both groups completed a walking intervention and home‐based resistance training (2x/week for 6‐months). The PT group performed resistance exercises with maximal intended concentric velocity, whereas the ST group maintained a slow (2‐s) concentric velocity. Results At 6‐months, weight loss was ~3 kg in both groups. Both groups significantly improved function (gz = 1.04‐1.93), strength (gz = 0.65‐1.77), power (gz = 0.66‐0.85), contraction velocity (gz = 0.65‐1.12) and QoL (gz = 0.62‐1.54). Between‐group differences in shoulder press velocity (‐0.09 m·s‐1, gs = ‐0.95 [‐1.63, ‐0.28]) and six‐minute walk test (‐16.9 m, gs = ‐0.51 [‐1.16, 0.13]) favoured the PT group. Conclusions Home‐based resistance training and walking leads to significant improvements in functional and psychological measures in adults with severe obesity. In addition, considering the between‐group effect sizes and their uncertainty, performing resistance exercises with maximal concentric speed is a simple adjustment to conventional resistance training that yields negligible negative effects but potentially large benefits on walking capacity and upper‐limb contraction velocity.

Modeling and simulation of two port proportional slip-in cartridge valve based on AMESim

Two port proportional slip-in cartridge valves are critical components of the heavy duty press hydraulic system. Their performance, especially the static flow rate under different valve opening size and the valve response time, is important to the press velocity control precision. So, it is necessary to build an accurate model of the valve to analyse different parameters’ influences on the valve performance. Based on the analysis of the valve structure and working principle, the valve model is established by the AMESim. The valve flow rate under different valve opening size ratio is calculated using the simulation model. The rated flow rate calculated by the simulation model is 0.33% less than the sample value, and the variation trend of the calculated flow rate curve is consistent with the manual curve. This demonstrates the considerable effectiveness of the valve simulation model. Then, the influences of the spring stiffness, the pilot oil pressure and the pilot valve gain on the valve poppet response time are analysed using the simulation model, respectively. This research may offer the basis for the whole hydraulic system building and control strategy designing.

Changes in Bench Press Velocity and Power After 8 Weeks of High-Load Cluster- or Traditional-Set Structures.

Davies, TB, Halaki, M, Orr, R, Helms, ER, and Hackett, DA. Changes in bench press velocity and power after 8 weeks of high-load cluster- or traditional-set structures. J Strength Cond Res 34(10): 2734-2742, 2020-This study investigated the effects of high-load cluster- vs. traditional-set structures using the bench press on velocity and power. Twenty-one resistance-trained individuals (male = 12, female = 9) performed a 3-week familiarization block followed by randomization into 1 of 2 upper- and lower-body split training routines performed for 8 weeks. The bench press was the only exercise manipulated with subjects using either cluster-set (CLUS, n = 11) or traditional-set (TRAD, n = 10) structures during training sessions. Subjects performed 4 sets of 5 repetitions at 85% 1 repetition maximum (1RM) with CLUS having a 30-second inter-repetition, and 3-minute interset rest while TRAD had a 5-minute interset rest. A load-velocity profile of relative loads derived from a 1RM test was used to assess velocity and power (absolute and relative to body mass) on the bench press. Significant improvements over time were found across various loads ranging from 45 to 75% 1RM for absolute and relative peak power (p = 0.006-0.041), and mean power (p = 0.001-0.032). Significant decreases over time were found at 55% 1RM and 65% 1RM for peak velocity (p = 0.027 and p = 0.012, respectively) and mean velocity (p = 0.047 and p = 0.022, respectively). There were no significant group or group by time interactions found for all outcomes. Within the context of high-load resistance training, set structure seems to be of less importance for changes in bench press velocity and power provided there is an intention to lift with maximal concentric velocity.

Habitual physical activity levels do not predict leg strength and power in healthy, active older adults.

Physical activity is considered crucial in attenuating losses in strength and power associated with ageing. However, in well-functioning, active older adults the relationship between habitual physical activity and muscle function is surprisingly unclear. Leg press velocity, force, and power, were compared between 50 older and 30 younger healthy individuals, and associations with habitual physical activity explored. An incremental power test was performed on a pneumatic leg press, with theoretical maximum velocity, force, and power calculated. Vastus lateralis muscle thickness was measured by ultrasound, and participants wore a combined accelerometer and heart rate monitor for 6-days of free-living. Older individuals produced lower absolute maximum velocity, force, and power, than younger individuals. When accounting for smaller muscle size, older individual’s maximum force and power remained markedly lower. Both groups were active, however using age specific thresholds for classifying physical activity, the older individuals engaged in twice the amount of moderate-to-vigorous physical activity in comparison to the younger individuals. There were no associations between any characteristics of muscle function and physical activity. These data support that the ability to generate force and power deteriorates with age, however habitual physical activity levels do not explain inter-individual differences in muscle function in active older individuals.

Investigation of the required clamping force at multidirectional undercut-forging

A hot forging process allows to produce parts of excellent quality and technical properties. Nevertheless, it is not possible to forge undercut geometries like piston pin bores, it is usually necessary to manufacture them in subsequent processes. Thus, an undercut-forging process was newly developed. Such a process requires a multidirectional forming tool, which is challenging due to a high clamping force of the tool during the process. With the research results, the requirements to the crucial tool components of heavy springs diminish, allowing using standard spring devices instead of large and expensive custom designed devices. The aim of this study is to analyze the clamping force, its origin, and influencing factors in order to facilitate the tool design. Therefore, in forming simulations the input parameters press velocity, initial temperature, and punch shape were investigated, and their effect on the clamping force was statistically evaluated. The press velocity has the major impact on the resulting clamping force. The initial part temperature and the shape of the punch tool showed minor but still significant effects. This combination of input parameters reduces the load and the stress on the tool, enabling to perform the process on smaller forging presses. Eventually, forging trials validated the results.

Effects of Pre-Workout Supplements on Power Maintenance in Lower Body and Upper Body Tasks

Recently, the use of pre-workout supplements has become popular. Research has shown their ability to increase performance for single bouts but little exists showing their ability to maintain this increase in performance over multiple bouts. Purpose: To investigate the effects of supplements on power production and the maintenance of upper and lower body tasks. Methods: Twenty-three males (22.9 ± 3.6 years, 175.6 ± 6.5 cm, 86.9 ± 15.1 kg, 19.1 ± 8.4 BF% mean ± standard deviation (SD)) were familiarized with the testing protocols and maximal bench press performances were attained (109.1 ± 34.0 kg). Utilizing a double-blind crossover design, subjects completed three trials of five countermovement vertical jumps before and after a high-intensity cycle sprint protocol, which consisted of ten maximal 5 s cycle ergometer sprints utilizing 7.5% of the subject’s body weight as resistance, with 55 s of recovery between each sprint. Subjects ingested in a randomized order a commercially available pre-workout supplement (SUP), placebo + 300 mg caffeine (CAF), or a placebo (PLA). Peak power (PP), mean power (MP), and minimum power (MNP) were recorded for each sprint. Subjects performed a velocity bench press test utilizing 80% of their predetermined one repetition maximum (1RM) for 10 sets of 3 repetitions for maximal speed, with one-minute rests between sets. Maximal velocity from each set was recorded. For analysis, bike sprint and bench press data were normalized to the placebo trial. Results: Cycle sprint testing showed no significant differences through the testing sessions. In the bench press, the peak velocity was higher with both the SUP and CAF treatments compared to the placebo group (1.09 ± 0.17 SUP, 1.10 ± 0.16 CAF, and 1 ± 0 PLA, p &lt; 0.05) and the supplement group was higher than the PLA for mean velocity (1.11 ± 0.18 SUP and 1 ± 0 PLA, p &lt; 0.05). Vertical jump performance and lactate levels were not significantly different (RMANOVA showed no significant differences from any treatments). Conclusions: Supplementation with a pre-workout supplement or placebo with caffeine showed positive benefits in performance in bench press velocity.

Investigation on the design of hydraulic high-speed punching press with a large press force and a long press stroke

High-speed punching presses are widely applied in modern manufacture industry, especially in occasions of automatic production with a large or a super large quality. To obtain a better production efficiency and a wilder application in industries, it is meaningful to develop the high-speed punching presses with a large press force and a long press stroke. Considering the limitations of mechanical and servo high-speed punching presses, hydraulic technology is the most possible way to develop the high-speed punching press with a large press force and a long press stroke so far. This article has proposed a hydraulic operating principle based on the hydraulic vibration technology for the development of the high-speed punching press with a press force of 1250 kN, a press stroke of 50 mm, and a press velocity of 1000 hpm. With a simulation model built under the AMESim environment, performances of the system are obtained and analyzed. Then, parameter optimization is also carried out and discussed. Finally, the operating principle and the parameters are refined. The obtained results have proved that the design meets the aimed performances of the high-speed punching press.

Ultrasonic-Assisted Upsetting of Steel with 15 kHz Oscillation Frequency

Common limitations in bulk metal forming processes are the maximum available press force and forming characteristics of metallic materials. Conventional measures to overcome those limitations, such as forming at elevated temperature, are not always applicable. An alternative approach is the use of a superimposed axial tool vibration with ultrasonic frequency. This enables a considerable reduction of required forming forces. The underlying mechanisms of this phenomenon have so far mainly been investigated for frequencies above 20 kHz and easily deformable materials, like copper. Due to limitations concerning the system technology, materials with higher strength have been considered only to a very limited extent. In order to allow investigations on the deformation behavior of materials with higher strength during ultrasonic-assisted upsetting, a tool setup containing a 15 kHz oscillating system has been developed. It offers a larger loading capacity in comparison to industrially available systems with higher frequency. Ultrasonic-assisted upsetting experiments with varying amplitude and press velocity are carried out to examine vibration-induced changes in the flow behavior of steel S235JR. Changes in the material characteristics are analyzed by evaluating the mean upsetting force as well as the microstructure of the upsetting specimen before and after forming. The resulting forces show a strong process dependence regarding the oscillation amplitude. The static press velocity and contact status between tool and specimen also influence the process forces, but to a much lower extent than the amplitude. Concerning the microstructure a rising oscillation amplitude leads to an increased radial elongation and axial compression of ferrite grains at the strongly deformed specimen center.

Optimization design preform billet shape of 7050 aluminum alloy giant plane forgings based on electric field method and MBC toolbox

The preform billet shape of the 7050 aluminum alloy giant plane forgings has been designed using electric field method based on similarity principle. Firstly, the electrostatic field was analysed by using ANSYS software, from which the preform billet shape was obtained based on electrostatic field equipotential lines. The preform shape, press velocity, temperature and friction factor were taken as parameter variables, while the forming load, filling rate and grain size were chosen as optimization goals. The mathematical model was optimized by the use of a Model-Based Calibration (MBC) toolbox for modelling, Three-Dimensional of Design Environment for FORMing (DEFORM-3D) for simulation and CAlibration GEneration (CAGE) toolbox, obtaining the best preform shape and the optimal combination of process parameters (friction factor μ = 0.2, press velocity ν = 9.8 mm/s and billet temperature T = 478 °C) when the equipotential line was ξ = 0.425 V. Finally, comparing with initial preform shape, the results indicate that the optimized preform billet designed by electric field method has an advantage in finish forging, while the forming load of finish forging reduces by about 38 % and the average micrograin size reduces by about 45 %. Therefore, it provides an effective method for designing preform billet shape of complex forgings.

Relationships Between Changes In Performance And Body Composition Variables After A Ten-week Resistance Training Intervention

Changes in body composition variables as well as strength and power performance are both apparent after resistance training interventions. PURPOSE: To compare multiple body composition variables and how they relate to changes in strength and power. METHODS: Eighteen trained men (25.8 ± 4.3y; 176.7 ± 5.0cm; 80.4 ± 12.0kg) completed a 10 week resistance training program. The first 8 weeks consisted of daily undulating periodized resistance training 3 days per week, focusing on either muscular hypertrophy, power, or strength. The final 2 weeks featured an overreach and taper phase. Tests consisted of 1RM strength of the bench press and leg press, a 30s Wingate, bench press peak power and velocity, and vertical jump height, peak power, and peak velocity. Body composition variables include total body and segmental Dual-Energy X-Ray Analysis (DXA), multi-frequency bioelectrical impedance (MFBIA), Single Frequency BIA (SFBIA), Bioimpedance Spectroscopy (BIS), Skinfold thicknesses, limb circumferences, and diagnostic ultrasound (US). RESULTS: With the exception of Wingate variables (p > 0.09), significant increases in strength and power were observed for all performance measurements (p < 0.01). Significant positive relationships were observed for MFBIA fat mass (FM) and MFBIA percent fat (%Fat) (r > 0.50, p < 0.03) for bench press velocity as well as for DXA trunk lean mass and leg press 1RM (r = 0.576, p = 0.012). Significant negative relationships were discovered for skinfold thicknesses of the suprailliac and vertical jump height (r = -0.507, p = 0.032) as well as US fat thickness and leg press 1RM (r = -0.711, p = 0.001). CONCLUSION: Changes in body composition variables (FM, FFM, %Fat, etc.) measured by different methods appear to produce varying relationships with performance variables after resistance training. An increase in fat measured by MFBIA appears to be associated with an increase in bench press velocity and an increase in trunk lean mass measured by DXA may predict an increase in leg strength. Also, a loss in subcutaneous hip (Skinfold) and thigh (US) fat may increase both vertical jump height and lower body strength, respectively. Thus, relationships between changes in body composition and performance after a resistance exercise intervention are dependent on both the method used as well as the variables being analyzed.

A Study Effect of Shooting 2 Balls in a Ball Swaging Process on Gram Load Parameter Using Finite Element Analysis

The purposes of this research are to explore the baseplate and actuator arm deformation which effect to the gram load which occur in the ball swaging process, the main component determining quality of assembly the head stack assembly with the actuator arm. By shooting a ball though the base plate, the component located on the head stack assembly, the base plate plastic deformation takes place and it in expand in radial direction. The base plate then adjoins with the actuator arm. Using the finite element method to reproduce the ball swaging process, we repeated to study effect of the swage press clamp and velocity. The study done by creating the three dimensionals finite element model to analyze and explain characteristics of the baseplate and actuator arm deformation which effect to gram load which effect to the ball swaging process.

Acute Effects of Static Stretching on Bench Press Power and Velocity in Adolescent Male Athletes

The purpose was to examine the acute effect of pre-exercise static stretching on barbell power and velocity during the bench press exercise. Forty male high school athletes performed 1 repetition maximum (1 RM) testing and were divided into either a static stretching (SS), or a no stretching (NS) protocol. Subjects performed 1 set of 3 repetitions of the bench press with 50% 1 RM as a warm-up. SS then performed a series of stretching exercises for the involved muscles. After completing either the bench press warm-up or the stretching protocol, subjects executed one bench press repetition at 85% 1 RM. After 24 hours, the groups switched protocols. Concentric mean barbell power and velocity were measured during the 85% lift. Stretching resulted in significantly lower mean power (NS=366.6±115.7 W, SS=282.7±111.4W) and mean velocity (NS=0.413±0.103 m×s−1, SS=0.302±0.086 m·s−1) when compared to NS. Static stretching has an acute detrimental effect on muscular performance.