Using three-dimensional kinematics to identify feedback for the Snatch: a case study.

This case study evaluated the importance of peak bar velocity and starting posture adopted by a novice weightlifter to the outcome of a Snatch lift. Multiple observations of both successful and unsuccessful attempts were captured using 3D motion analysis (VICON MX: 500 Hz). The following data analysis was then used to derive feedback. In total, 133 attempts of loads ranging from 75 to 100% of 1 repetition maximum (1RM) were performed by the subject (age = 25 years, stature = 171 cm, mass = 74.8 kg, Snatch 1RM = 80 kg). Variables included peak bar velocity, pelvis, hip, knee and ankle joint angles at the starting position for the right side and the difference between (left minus right) sides. No main effects for load, success, or their interactions were found for peak bar velocity. Starting position kinematics were mostly nonsignificant between the outcome of Snatch attempts. Right ankle joint angle was the only exception, where unsuccessful attempts displayed greater (p = 0.0228) dorsiflexion. A more comprehensive finding was achieved through the partition modeling; this analysis provided valuable insight and coaching feedback for the subject in relation to his lower body kinematics at the starting position. Furthermore, the accuracy of this feedback was verified using a holdback data set. Specifically, anterior pelvic tilt (>17.6°) and hip joint (<89.6°) angle were identified as the key features to increasing the likelihood of success. In conclusion, this case study outlines a method of data collection and analysis to assist coaching feedback for an individual.

Relationship between velocity reached at VO2(max) and time-trial performances in elite Australian Rules footballers.

PURPOSE: Running velocity reached at maximal oxygen uptake (vVO2(max)) can be a useful measure to prescribe training intensity for aerobic conditioning. Obtaining it in the laboratory is often not practical, and average velocities from time trials are an attractive alternative. To date, the efficacies of such practices for team sport players are unknown. This study aimed to assess the relationship between vVO2(max) obtained in the laboratory against two time-trial estimates (1500 m and 3200 m). METHODS: During the early preseason, elite Australian Rules football players (n = 23, 22.7 +/- 3.4 y, 187.7 +/- 8.2 cm, 75.5 +/- 9.2 kg) participated in a laboratory test on a motorized treadmill and two outdoor time trials. RESULTS: Based on average velocity the 1500-m time-trial performance (5.01 +/- 0.23 m x s(-1)) overestimated (0.36 m x s(-1), d = 1.75), whereas the 3200-m time trial (4.47 +/- 0.23 m x s(-1)) underestimated (0.17 m x s(-1), d = 0.83) the laboratory vVO2(max) (4.64 +/- 0.18 m x s(-1)). Despite these differences, both 1500-m and 3200-m time-trial performances correlated with the laboratory measure (r = -0.791; r = -0.793 respectively). Both subsequent linear regressions were of good fit and predicted the laboratory measure within +/- 0.12 m x s(-1). CONCLUSION: Estimates of vVO2(max) should not be used interchangeably, nor should they replace the laboratory measure. When laboratory testing is not accessible for team sports players, prescription of training intensity may be more accurately estimated from linear regression based on either 1500-m or 3200-m time-trial performance than from the corresponding average velocity.

Reliability of the Ekblom soccer-specific endurance test.

The aim of this study was to explore and quantify measurement reliability of the Ekblom endurance test. Experienced university soccer players (n = 19; age = 20.5 +/- 2.5 years; mass = 80.4 +/- 9.8 kg; and stature = 179.0 +/- 6.0 cm) completed the Ekblom endurance test on 3 separate occasions. Time to complete trial 1 (549 +/- 26 seconds) and trial 2 (547 +/- 26 seconds) was analyzed, and despite no significant difference (F1,18 = 4.119, p = 0.057, etaP = 0.186) between trials, some evidence of systematic bias was observed in the data. Therefore, trial 2 data were compared with those of trial 3 (548 +/- 27 seconds), with trial 1 data removed. The subsequent analysis (F1,18 = 0.740, p = 0.401, etaP = 0.039) showed a reduction in the risk of making a type II error when compared with the previous analysis. From the reliability analyses (3,1 intraclass correlation = 0.983, SEM = +/-3 seconds, smallest worthwhile change = 5 seconds, standard error of prediction [95% confidence intervals] = +/- 9 seconds), a high level of measurement reliability was observed and the sensitivity of the test to monitor changes was "good." In summary, it was shown that a test that involves a variety of soccer-specific forms of locomotion can be highly reliable and sensitive to detect change. In light of the systematic bias found, we do, however, recommend a familiarization session to be scheduled before the introduction of this test.