The influence of different relative intensities on power output was investigated in the present study in order to identify the optimal load that maximizes power output during the hang power clean. Fifteen men (age: 22.1 +/- 2.0 years, height: 180.1 +/- 6.3 cm, and body mass: 89.4 +/- 14.7 kg) performed the hang power cleans on a forceplate at 30-90% of one repetition maximum (1RM). Peak power was maximized at 70% 1RM, which was, however, not significantly different from peak power at 50, 60, 80, and 90% 1RM. Average power also was maximized at 70% 1RM, which was not significantly different from average power at 40, 50, 60, 80, and 90% 1RM. It was concluded that (a) the relative intensity had a significant influence on power output, and (b) power output can be maximized at a submaximal load during the hang power clean.

In this study, we compared sprint kinematics of sled towing and vest sprinting with the same relative loads. Twenty athletes performed 30-m sprints in three different conditions: (a) un-resisted, (b) sled towing, and (c) vest sprinting. During sled towing and vest sprinting, external loads of 15% and 20% of body mass were used. Sprint times were recorded over 10 and 30 m. Sagittal-plane high-speed video data were recorded at 5, 15, and 25 m from the start. Relative to the un-resisted condition, sprint time increased (7.5 to 19.8%) in both resisted conditions, resulting mainly from decreased step length (-5.2 to -16.5%) with small decreases in step frequency (-2.7 to -6.1%). Sled towing increased stance phase duration (14.7 to 26.0%), trunk angle (12.5 to 71.5%), and knee angle (10.3 to 22.7%), and decreased swing phase duration (-4.8 to -15.2%) relative to the un-resisted condition. Vest sprinting increased stance phase duration (12.8 to 24.5%) and decreased swing phase duration (-8.4 to -14.4%) and trunk angle (-1.7 to -13.0%). There were significant differences between the two resisted conditions in trunk, thigh, and knee angles. We conclude that sled towing and vest sprinting have different effects on some kinematics and hence change the overload experienced by muscle groups.

The primary purpose of this study was to investigate whether the athlete who has high performance in hang power clean, a common weightlifting exercise, has high performances in sprinting, jumping, and changing of direction (COD). As the secondary purpose, relationships between hang power clean performance, maximum strength, power and performance of jumping, sprinting, and COD also were investigated. Twenty-nine semiprofessional Australian Rules football players (age, height, and body mass [mean +/- SD]: 21.3 +/- 2.7 years, 1.8 +/- 0.1 m, and 83.6 +/- 8.2 kg) were tested for one repetition maximum (1RM) hang power clean, 1RM front squat, power output during countermovement jump with 40-kg barbell and without external load (CMJ), height of CMJ, 20-m sprint time, and 5-5 COD time. The subjects were divided into top and bottom half groups (n = 14 for each group) based on their 1RM hang power clean score relative to body mass, then measures from all other tests were compared with one-way analyses of variance. In addition, Pearson's product moment correlations between measurements were calculated among all subjects (n = 29). The top half group possessed higher maximum strength (P < 0.01), power (P < 0.01), performance of jumping (P < 0.05), and sprinting (P < 0.01). However, there was no significant difference between groups in 5-5 COD time, possibly because of important contributing factors other than strength and power. There were significant correlations between most of, but not all, combinations of performances of hang power clean, jumping, sprinting, COD, maximum strength, and power. Therefore, it seems likely there are underlying strength qualities that are common to the hang power clean, jumping, and sprinting.

Force platforms are used extensively to measure force and power output during countermovement jump (CMJ). The purpose of this study was to examine measurement reliability and validity of commonly used performance measurements derived from ground reaction force (GRF)-time data during CMJ and the influence of sampling at different frequencies. Twenty-four men performed 2 trials of CMJ on a force platform, and GRF-time data were sampled at a rate of 500 Hz. Data obtained at 500 Hz were considered as the reference, and then data were resampled at 400, 250, 200, 100, 50, and 25 Hz, using interpolation. Commonly used power, force, and velocity performance measures were obtained from GRF-time data. Reliability was assessed by intraclass correlation coefficient (ICC) and coefficient of variation (CV) between the 2 trials within the session. Peak power, peak force, and peak velocity were highly reliable across all sampling frequencies (ICC = 0.92-0.98, CV = 1.3-4.1). Percentage differences from 500-Hz reference values ranged from -0.85 to 0.20% at 400 Hz, -1.88 to 0.89% at 250 Hz, -1.80 to 1.31% at 200 Hz, -3.63 to 3.34% at 100 Hz, -11.37 to 6.51% at 50 Hz, and -13.17 to 9.03% at 25 Hz. In conclusion, peak power, force, and velocity measurements derived from GRF to assess leg extensor capabilities are reliable within a test session except for peak rate of force development and time to peak power. With regard to sampling frequency, scientists and practitioners may consider sampling as low as 200 Hz, depending on the purpose of measurement, because the percentage difference is not markedly enlarged until the frequency is 100 Hz or lower.

Six elite women weightlifters were tested to evaluate force-time curve characteristics and intercorrelations of isometric and dynamic muscle actions. Subjects performed isometric and dynamic mid-thigh clean pulls at 30% of maximal isometric peak force and 100 kg from a standardized position on a 61.0 x 121.9 cm AMTI forceplate. Isometric peak force showed strong correlations to the athletes' competitive snatch, clean and jerk, and combined total (r = 0.93, 0.64, and 0.80 respectively). Isometric rate of force development showed moderate to strong relationships to the athletes' competitive snatch, clean and jerk, and combined total (r = 0.79, 0.69, and 0.80 respectively). The results of this study suggest that the ability to perform maximal snatch and clean and jerks shows some structural and functional foundation with the ability to generate high forces rapidly in elite women weightlifters.