Methodological concerns for determining power output in the jump squat

The purpose of this study was to investigate the validity of power measurement techniques during the jump squat (JS) utilizing various combinations of a force plate and linear position transducer (LPT) devices. Nine men with at least 6 months of prior resistance training experience participated in this acute investigation. One repetition maximums (1RM) in the squat were determined, followed by JS testing under 2 loading conditions (30% of 1RM [JS30] and 90% of 1RM [JS90]). Three different techniques were used simultaneously in data collection: (a) 1 linear position transducer (1-LPT); (b) 1 linear position transducer and a force plate (1-LPT + FP); and (c) 2 linear position transducers and a force place (2-LPT + FP). Vertical velocity-, force-, and power-time curves were calculated for each lift using these methodologies and were compared. Peak force and peak power were overestimated by 1-LPT in both JS30 and JS90 compared with 2-LPT + FP and 1-LPT + FP (p 相似文献   

Peak power, force, and velocity during jump squats in professional rugby players

Training at the optimal load for peak power output (PPO) has been proposed as a method for enhancing power output, although others argue that the force, velocity, and PPO are of interest across the full range of loads. The aim of this study was to examine the influence of load on PPO, peak barbell velocity (BV), and peak vertical ground reaction force (VGRF) during the jump squat (JS) in a group of professional rugby players. Eleven male professional rugby players (age, 26 ± 3 years; height, 1.83 ± 6.12 m; mass, 97.3 ± 11.6 kg) performed loaded JS at loads of 20-100% of 1 repetition maximum (1RM) JS. A force plate and linear position transducer, with a mechanical braking unit, were used to measure PPO, VGRF, and BV. Load had very large significant effects on PPO (p < 0.001, partial η2 = 0.915); peak VGRF (p < 0.001, partial η2 = 0.854); and peak BV (p < 0.001, partial η2 = 0.973). The PPO and peak BV were the highest at 20% 1RM, though PPO was not significantly greater than that at 30% 1RM. The peak VGRF was significantly greater at 1RM than all other loads, with no significant difference between 20 and 60% 1RM. In resistance trained professional rugby players, the optimal load for eliciting PPO during the loaded JS in the range measured occurs at 20% 1RM JS, with decreases in PPO and BV, and increases in VGRF, as the load is increased, although greater PPO likely occurs without any additional load.     

The influence of body mass on calculation of power during lower-body resistance exercises

The objective of this investigation was to examine the influence of body mass in the calculation of power and the subsequent effect on the load-power relationship in the jump squat, squat, and power clean. Twelve Division I male athletes were evaluated on their performance across various intensities in all the 3 lifts. Power output was calculated using 3 separate techniques: (a) including the contribution of body mass in force output (IBM), (b) including the contribution of the mass of body less the mass of the shanks and feet in force output (IBMS), and (c) excluding the contribution of body mass in force output (EBM). Peak power, peak power relative to body mass, and peak force calculated using EBM were significantly (p < or = 0.05) lower than outputs calculated with IBM and IBMS. The load that maximized power output was unchanged between the 3 techniques in the jump squat (0% 1 repetition maximum [1RM]) and power clean (80% 1RM) but was shifted from 56% (IBM and IBMS) to 71% 1RM (EBM) in the squat. Across all 3 movements, the shape of the load-power curve was affected when derived via the EBM method as a result of the underrepresentation of power output at light loads. This was due to the majority of the load being neglected when the mass of the body was removed from the system mass used in the calculation of force. This study indicates that not only is the actual power output significantly lower when body mass is excluded from the force output of a lower body movement, but the load-power relationship is altered as well. Therefore, it is imperative that the mass of the individual being tested is incorporated into the calculation of force used to determine power output during lower-body movements.     

Validity of the Myotest® in measuring force and power production in the squat and bench press

The purpose of this study was to verify the concurrent validity of a bar-mounted Myotest? instrument in measuring the force and power production in the squat and bench press exercises when compared to the gold standard of a computerized linear transducer and force platform system. Fifty-four men (bench press: 39-171 kg; squat: 75-221 kg) and 43 women (bench press: 18-80 kg; squat: 30-115 kg) (age range 18-30 years) performed a 1 repetition maximum (1RM) strength test in bench press and squat exercises. Power testing consisted of the jump squat and the bench throw at 30% of each subject's 1RM. During each measurement, both the Myotest? instrument and the Celesco linear transducer of the directly interfaced BMS system (Ballistic Measurement System [BMS] Innervations Inc, Fitness Technology force plate, Skye, South Australia, Australia) were mounted to the weight bar. A strong, positive correlation (r) between the Myotest and BMS systems and a high correlation of determination (R2) was demonstrated for bench throw force (r = 0.95, p < 0.05) (R2 = 0.92); bench throw power (r = 0.96, p < 0.05) (R2 = 0.93); squat jump force (r = 0.98, p < 0.05) (R2 = 0.97); and squat jump power (r = 0.91, p < 0.05) (R2 = 0.82). In conclusion, when fixed on the bar in the vertical axis, the Myotest is a valid field instrument for measuring force and power in commonly used exercise movements.     

Comparison of kinetic variables and muscle activity during a squat vs. a box squat

The purpose of this investigation was to determine if there was a difference in kinetic variables and muscle activity when comparing a squat to a box squat. A box squat removes the stretch-shortening cycle component from the squat, and thus, the possible influence of the box squat on concentric phase performance is of interest. Eight resistance trained men (Height: 179.61 ± 13.43 cm; Body Mass: 107.65 ± 29.79 kg; Age: 24.77 ± 3.22 years; 1 repetition maximum [1RM]: 200.11 ± 58.91 kg) performed 1 repetition of squats and box squats using 60, 70, and 80% of their 1RM in a randomized fashion. Subjects completed the movement while standing on a force plate and with 2 linear position transducers attached to the bar. Force and velocity were used to calculate power. Peak force and peak power were determined from the force-time and power-time curves during the concentric phase of the lift. Muscle activity (electromyography) was recorded from the vastus lateralis, vastus medialis, biceps femoris, and longissimus. Results indicate that peak force and peak power are similar between the squat and box squat. However, during the 70% of 1RM trials, the squat resulted in a significantly lower peak force in comparison to the box squat (squat = 3,269 ± 573 N, box squat = 3,364 ± 575 N). In addition, during the 80% of 1RM trials, the squat resulted in significantly lower peak power in comparison to the box squat (squat = 2,050 ± 486 W, box squat = 2,197 ± 544 W). Muscle activity was generally higher during the squat in comparison to the box squat. In conclusion, minimal differences were observed in kinetic variables and muscle activity between the squat and box squat. Removing the stretch-shortening cycle during the squat (using a box) appears to have limited negative consequences on performance.     

Occurrence of fatigue during sets of static squat jumps performed at a variety of loads

Research has identified that the optimal power load for static squat jumps (with no countermovement) is lower than the loads usually recommended for power training. Lower loads may permit the performance of additional repetitions before the onset of fatigue compared with heavier loads; therefore, the aim of this study was to determine the point of fatigue during squat jumps at various loads (0, 20, 40, 60% 1-repetition maximum [1RM]). Seventeen professional rugby league players performed sets of 6 squat jumps (with no countermovement), using 4 loading conditions (0, 20, 40, and 60% of 1RM back squat). Repeated measures analysis of variance revealed no significant differences (p > 0.05) in force, velocity, power, and displacement between repetitions, for the 0, 20, and 40% loading conditions. The 60% condition showed no significant difference (p > 0.05) in peak force between repetitions; however, velocity (1.12 + 0.10 and 1.18 + 0.11 m·s(-1)), power (3,385 + 343 and 3,617 + 396 W) and displacement (11.13 + 2.31 and 11.85 + 2.16 cm) were significantly (p < 0.02) lower during repetition 6 compared with repetition 2. These findings indicate that when performing squat jumps (with no countermovement) with a load <40% 1RM back squat, up to >6 repetitions can be completed without inducing fatigue and a minimum of 4-6 repetitions should be performed to achieve peak power output. When performing squat jumps (with no countermovement) with a load equal to the 60% 1RM only, 5 repetitions should be performed to minimize fatigue and ensure maintenance of velocity and power.     

Anthropometrical, physiological, and tracked power profiles of elite taekwondo athletes 9 weeks before the Olympic competition phase

Physiological, anthropometric, and power profiling data were retrospectively analyzed from 4 elite taekwondo athletes from the Australian National Olympic team 9 weeks from Olympic departure. Power profiling data were collected weekly throughout the 9-week period. Anthropometric skinfolds generated a lean mass index (LMI). Physiological tests included a squat jump and bench throw power profile, bleep test, 20-m sprint test, running VO2max test, and bench press and squat 3 repetition maximum (3RM) strength tests. After this, the athletes power, velocity, and acceleration profile during unweighted squat jumps and single-leg jumps were tracked using a linear position transducer. Increases in power, velocity, and acceleration between weeks and bilateral comparisons were analyzed. Athletes had an LMI of 37.1 ± 0.4 and were 173.9 ± 0.2 m and 67 ± 1.1 kg. Relatively weaker upper body (56 ± 11.97 kg 3RM bench press) compared to lower body strength (88 ± 2.89 kg 3RM squat) was shown alongside a VO2max of 53.29 ml(-1)·min(-1)·kg, and a 20-m sprint time of 3.37 seconds. Increases in all power variables for single-leg squat and squat jumps were found from the first session to the last. Absolute peak power in single-leg squat jumps increased by 13.4-16% for the left and right legs with a 12.9% increase in squat jump peak power. Allometrically scaled peak power showed greater increases for single-leg (right leg: 18.55%; left: 23.49%) and squat jump (14.49%). The athlete's weight did not change significantly throughout the 9-week mesocycle. Progressions in power increases throughout the weeks were undulating and can be related to the intensity of the prior week's training and athlete injury. This analysis has shown that a 9-week mesocycle before Olympic departure that focuses on core lifts has the ability to improve power considerably.     

Relationship between countermovement jump performance and multijoint isometric and dynamic tests of strength

The purpose of this investigation was to determine the relationship between countermovement vertical jump (CMJ) performance and various methods used to assess isometric and dynamic multijoint strength. Twelve NCAA Division I-AA male football and track and field athletes (age, 19.83 +/- 1.40 years; height, 179.10 +/- 4.56 cm; mass, 90.08 +/- 14.81 kg; percentage of body fat, 11.85 +/- 5.47%) participated in 2 testing sessions. The first session involved 1 repetition maximum (1RM) (kg) testing in the squat and power clean. During the second session, peak force (N), relative peak force (N x kg(-1)), peak power (W), relative peak power (W x kg(-1)), peak velocity (m x s(-1)), and jump height (meters) in a CMJ, and peak force and rate of force development (RFD) (N x s(-1)) in a maximal isometric squat (ISO squat) and maximal isometric mid-thigh pull (ISO mid-thigh) were assessed. Significant correlations (P < or = 0.05) were found when comparing relative 1RMs (1RM/body mass), in both the squat and power clean, to relative CMJ peak power, CMJ peak velocity, and CMJ height. No significant correlations existed between the 4 measures of absolute strength, which did not account for body mass (squat 1RM, power clean 1RM, ISO squat peak force, and ISO mid-thigh peak force) when compared to CMJ peak velocity and CMJ height. In conclusion, multijoint dynamic tests of strength (squat 1RM and power clean 1RM), expressed relative to body mass, are most closely correlated with CMJ performance. These results suggest that increasing maximal strength relative to body mass can improve performance in explosive lower body movements. The squat and power clean, used in a concurrent strength and power training program, are recommended for optimizing lower body power.     

Eight weeks of ballistic exercise improves power independently of changes in strength and muscle fiber type expression

This study investigated the effects of ballistic resistance training and strength training on muscle fiber composition, peak force (PF), maximal strength, and peak power (PP). Fourteen males (age = 21.3 +/- 2.9, body mass = 77.8 +/- 10.1 kg) with 3 months of resistance training experience completed the study. Subjects were tested pre and post for their squat one-repetition maximum (1RM) and PP in the jump squat (JS). Peak force and rate of force development (RFD) were tested during an isometric midthigh pull. Muscle biopsies were obtained from the vastus lateralis for analysis of muscle fiber type expression. Subjects were matched for strength and then randomly selected into either training (T) or control (C) groups. Group T performed 8 weeks of JS training using a periodized program with loading between 26 and 48% of 1RM, 3 days per week. Group T showed significant improvement in PP from 4088.9 +/- 520.6 to 5737.6 +/- 651.8 W. Rate of force development improved significantly in group T from 12687.5 +/- 4644.0 to 25343.8 +/- 12614.4 N x s(-1). PV improved significantly from 1.59 +/- 0.41 to 2.11 +/- 0.75 m x s(-1). No changes occurred in PF, 1RM, or muscle fiber type expression for group T. No changes occurred in any variables in group C. The results of this study indicate that using ballistic resistance exercise is an effective method for increasing PP and RFD independently of changes in maximum strength (1RM, PF), and those increases are a result of factors other than changes in muscle fiber type expression.     

Effectiveness of the 1RM estimation method based on isometric squat using a back-dynamometer

This study aimed to clarify the relationships between isometric squat (IS) using a back dynamometer and 1 repetition maximum (1RM) squat for maximum force and muscle activities and to examine the effectiveness of a 1RM estimation method based on IS. The subjects were 15 young men with weight training experience (mean age 20.7 ± 0.8 years, mean height 171.3 ± 4.4 cm, mean weight 64.4 ± 8.4 kg). They performed the IS with various stance widths and squat depths. The measured data of exerted maximum force and the action potential of the agonist muscles were compared with the 1RM squat data. The exerted maximum force during IS was significantly larger in wide stance (140% shoulder width) than in narrow stance (5-cm width). The maximum force was significantly larger with decreased knee flexion. As for muscle activity, the % root mean square value of muscle electric potential of the rectus femoris and the vastus lateralis tended to be higher in wide stance. As for exerted maximum force, wide stance and parallel depth in IS showed a significant and high correlation (r = 0.73) with 1RM squat. Simple linear regression analysis revealed a significant estimated regression equation [Y = 0.992X + 30.3 (Y:1RM, X:IS)]. However, the standard error of an estimate value obtained by the regression equation was very large (11.19 kg). In conclusion, IS with wide stance and parallel depth may be useful for the estimation of 1RM squat. However, estimating a 1RM by IS using a back dynamometer may be difficult.     

Changes in bar-path kinematics and kinetics after power-clean training

The purpose of this study was to investigate the direction and magnitude of kinematic changes in bar path and kinetic variable changes in the power clean (PC) after 4 weeks of PC training. Eighteen healthy adult men who had a minimum of 1 year of previous experience in the PC participated as subjects in this study. The subjects were pretested for their 1 repetition maximum (1RM) and provided with visual and verbal cues during PC training sessions, which took place 3 times per week for 4 weeks. Variables measured during data collection include pre- and post-peak force, peak power, and several bar-path kinematic variables through videography at 50, 70, and 90% of the subjects' pre-1RM. Peak force was improved at 50% of 1RM from 936 +/- 338 N to 1,299 +/- 384 N, at 70% from 1,216 +/- 315 N to 1,395 +/- 331 N, and at 90% from 1,255 +/- 329 N to 1,426 +/- 321 N. Peak power was increased at 50% of 1RM from 3,430 +/- 1,280 W to 4,230 +/- 1,326 W. All variables with respect to bar-path kinematics were improved significantly. These results indicate that both kinematic and kinetic variables improve through training and feedback. It is possible that persons beginning the PC exercise or coaches who provide instruction on the PC to beginning lifters should focus on proper bar path during the movement. This may result in force and power output to develop as technique improves. However, further investigation is required to establish the link between bar-path changes and kinetic variable performance improvements.     

Comparison of muscle force production using the Smith machine and free weights for bench press and squat exercises

The Smith machine (SM) (vertical motion of bar on fixed path; fixed-form exercise) and free weights (FWs) (free-form path) are commonly used strength training modes. Exercisers may need to alternate between types of equipment, depending on testing, training, rehabilitation, and/or the exercisers' goals. The purposes of this study were to compare muscle force production for SM and FWs using a 1 repetition maximum (1RM) for the parallel back squat and supine bench press exercises and to predict the 1RM for one mode from 1RM on the other mode. Men (n = 16) and women (n = 16) alternately completed 1RM testing for squat and bench press using SM and FWs. Analyses of variance (type of equipment x sex) and linear regression models were calculated. A significant difference was found between bench press and squat 1RMs for each mode of equipment for all participants. The squat 1RM was greater for the SM than the FWs; conversely, the bench 1RM was greater for FWs than the SM. When sex was considered, bench 1RM for FWs was greater than SM for men and women. The squat 1RM was greater for SM than FWs for women only. The 1RM on one mode of equipment was the best predictor of 1RM for the other mode. For both sexes, the equation SM bench 1RM (in kilograms) = -6.76 + 0.95 (FW bench 1RM) can be used. For women only, SM squat 1RM (in kilograms) = 28.3 + 0.73 (FW squat 1RM). These findings provide equations for converting between SM and FW equipment for training.     

Acute effects of augmented eccentric loading on jump squat performance

The purpose of this study was to determine the acute effects of a spectrum of eccentric loads on force, velocity, and power during the concentric portion of maximal-effort jump squats utilizing a repeated measures design. Thirteen resistance-trained men (age = 22.8 +/- 2.9 years, weight = 87.1 +/- 11.8 kg, 163.5 +/- 28.6 kg squat 1 repetition maximum [1RM]; mean +/- SD), who routinely incorporated back squats into their training, participated as subjects in this investigation. Jump squat performance was assessed using 4 experimental conditions. The first of these conditions consisted of an isoinertial load equal to 30% of back squat 1RM. The remaining conditions consisted of jump squats with a concentric load of 30% 1RM, subsequent to the application of experimental augmented eccentric loading (AEL) conditions of 20, 50, and 80% of back squat 1RM, respectively. All subjects performed 2 sets of 1RM of maximum-effort jump squats with all experimental conditions in a counter-balanced sequence. Forty-eight hours after completing the first testing session, subjects repeated the experimental testing protocol to establish stability reliability. Peak performance values for the reliable variables of force, velocity, and power, as well as force and power values obtained at 20-ms intervals during the initial 400 ms of the concentric jump squat range of motion, showed no statistical difference (p > 0.05) across the experimental AEL loads. These results suggest that load-spectrum AEL prior to a 30% 1RM jump squat fails to acutely enhance force, velocity, and power.     

The effect of heavy- vs. light-load jump squats on the development of strength, power, and speed

The purpose of this investigation was to examine the effect of an 8-week training program with heavy- vs. light-load jump squats on various physical performance measures and electromyography (EMG). Twenty-six athletic men with varying levels of resistance training experience performed sessions of jump squats with either 30% (JS30, n = 9) or 80% (JS80, n = 10) of their one repetition maximum in the squat (1RM) or served as a control (C, n = 7). An agility test, 20-m sprint, and jump squats with 30% (30J), 55% (55J), and 80% (80J) of their 1RM were performed before and after training. Peak force, peak velocity (PV), peak power (PP), jump height, and average EMG (concentric phase) were calculated for the jumps. There were significant increases in PP and PV in the 30J, 55J, and 80J for the JS30 group (p 相似文献   

Change in power output across a high-repetition set of bench throws and jump squats in highly trained athletes

Athletes experienced in maximal-power and power-endurance training performed 1 set of 2 common power training exercises in an effort to determine the effects of moderately high repetitions upon power output levels throughout the set. Twenty-four and 15 athletes, respectively, performed a set of 10 repetitions in both the bench throw (BT P60) and jump squat exercise (JS P60) with a resistance of 60 kg. For both exercises, power output was highest on either the second (JS P60) or the third repetition (BT P60) and was then maintained until the fifth repetition. Significant declines in power output occurred from the sixth repetition onwards until the 10th repetition (11.2% for BT P60 and 5% for JS P60 by the 10th repetition). These findings suggest that athletes attempting to increase maximal power limit their repetitions to 2 to 5 when using resistances of 35 to 45% 1RM in these exercises.     

Role of concentric force in limiting improvement in muscular strength

We hypothesized that resistance training with combined eccentric and concentric actions, and concentric action only, should yield similar changes in muscular strength. Subjects in a free weight group trained three times a week for 12 wk with eccentric and concentric actions (FW, n = 16), a second group trained with concentric-only contractions using hydraulic resistance (HY; n = 12), and a control group did not train (n = 11). Training for FW and HY included five sets of supine bench press and upright squat at an intensity of 1-6 repetition maximum (RM) plus five supplementary exercises at 5-10 RM for a total of 20 sets per session for approximately 50 min. Testing at pre-, mid-, and posttraining included 1) 1 RM bench press and squat with and 2) without prestretch using free weights; 3)isokinetic peak force and power for bench press and squat at 5 degrees/s, and isotonic peak velocity and power for bench press with 20-kg load and squat with 70-kg load; 4) hydraulic peak bench press force and power, and peak knee extension torque and power at fast and slow speeds; and 5) surface anthropometry (fatfolds and girths to estimate upper arm and thigh volume and muscle area). Changes in overall fatness, muscularity, and muscle + bone cross-sectional area of the limbs did not differ between groups (P greater than 0.05). Improvements in free weight bench press and squat were similar (P greater than 0.05) in FW (approximately 24%) and HY (approximately 22%, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Power and maximum strength relationships during performance of dynamic and static weighted jumps

The purpose of this study was to investigate the relationship of the 1 repetition maximum (1RM) squat to power output during countermovement and static weighted vertical squat jumps. The training experience of subjects (N = 22, 87.0 +/- 15.3 kg, 14.1 +/- 7.1% fat, 22.2 +/- 3.8 years) ranged from 7 weeks to 15+ years. Based on the 1RM squat, subjects were further divided into the 5 strongest and 5 weakest subjects (p 相似文献   

The effect of loading on kinematic and kinetic variables during the midthigh clean pull

The ability to develop high levels of muscular power is considered a fundamental component for many different sporting activities; however, the load that elicits peak power still remains controversial. The primary aim of this study was to determine at which load peak power output occurs during the midthigh clean pull. Sixteen participants (age 21.5 ± 2.4 years; height 173.86 ± 7.98 cm; body mass 70.85 ± 11.67 kg) performed midthigh clean pulls at intensities of 40, 60, 80, 100, 120, and 140% of 1 repetition maximum (1RM) power clean in a randomized and balanced order using a force plate and linear position transducer to assess velocity, displacement, peak power, peak force (Fz), impulse, and rate of force development (RFD). Significantly greater Fz occurred at a load of 140% (2,778.65 ± 151.58 N, p < 0.001), impulse within 100, 200, and 300 milliseconds at a load of 140% 1RM (196.85 ± 76.56, 415.75 ± 157.56, and 647.86 ± 252.43 N·s, p < 0.023, respectively), RFD at a load of 120% (26,224.23 ± 2,461.61 N·s, p = 0.004), whereas peak velocity (1.693 ± 0.042 m·s, p < 0.001) and peak power (3,712.82 ± 254.38 W, p < 0.001) occurred at 40% 1RM. Greatest total impulse (1,129.86 ± 534.86 N·s) was achieved at 140% 1RM, which was significantly greater (p < 0.03) than at all loads except the 120% 1RM condition. Results indicate that increased loading results in significant (p < 0.001) decreases in peak power and peak velocity during the midthigh clean pull. Moreover, if maximizing force production is the goal, then training at a higher load may be advantageous, with peak Fz occurring at 140% 1RM.     

Postactivation potentiation response in athletic and recreationally trained individuals

To determine if training status directly impacted the response to postactivation potentiation, athletes in sports requiring explosive strength (ATH; n = 7) were compared to recreationally trained (RT; n = 17) individuals. Over the course of 4 sessions, subjects performed rebound and concentric-only jump squats with 30%, 50%, and 70% 1 RM loads. Jump squats were performed 5 minutes and 18.5 minutes following control or heavy load warm-ups. Heavy load warm-up consisted of 5 sets of 1 repetition at 90% 1 RM back squat. Jump squat performance was assessed with a force platform and position transducer. Heavy load warm-up did not have an effect on the subjects as a single sample. However, when percent potentiation was compared between ATH and RT groups, force and power parameters were significantly greater for ATH (p < 0.05). Postactivation potentiation may be a viable method of acutely enhancing explosive strength performance in athletic but not recreationally trained individuals. Reference Data: Chiu, L.Z.F., A.C. Fry, L.W. Weiss, B.K. Schilling, L.E. Brown, and S.L. Smith. Postactivation potentiation response in athletic and recreationally trained individuals.     

Comparison of four different methods to measure power output during the hang power clean and the weighted jump squat

Measurement of power output during resistance training is becoming ubiquitous in strength and conditioning programs, but there is great variation in the methods used. The main purposes of this study were to compare the power output values obtained from 4 different methods and to examine the relationships between these values. Male semiprofessional Australian rules football players (n = 30) performed hang power clean and weighted jump squat while ground reaction force (GRF)-time data and barbell displacement-time data were sampled simultaneously using a force platform and a linear position transducer attached to the barbell. Peak and mean power applied to the barbell was obtained from barbell displacement-time data (method 1). Peak and mean power applied to the system (barbell + lifter) was obtained from 3 other methods: (a) using GRF-time data (method 2), (b) using barbell displacement-time data (method 3), and (c) using both barbell displacement-time data and GRF-time data (method 4). The peak power values (W) obtained from methods 1, 2, 3, and 4 were (mean +/- SD) 1,644 +/- 295, 3,079 +/- 638, 3,821 +/- 917, and 4,017 +/- 833 in hang power clean and 1,184 +/- 115, 3,866 +/- 451, 3,567 +/- 494, and 4,427 +/- 557 in weighted jump squat. There were significant differences between power output values obtained from method 1 vs. methods 2, 3, and 4, as well as method 2 vs. methods 3 and 4. The power output applied to the barbell and that applied to the system was significantly correlated (r = 0.65-0.81). As a practical application, it is important to understand the characteristics of each method and consider how power output should be measured during the hang power clean and the weighted jump squat.