Olympic weightlifting has been subject to rigorous academic and applied sporting research for over 40 years. Biomechanists have concerned themselves with Olympic weightlifting due to the complex coordination requirements coupled with high levels of full-body muscular activity. Motivated by Enoka's (1988) research on load- and skill-related changes; we used modern three-dimensional motion capture to assess selected mechanical characteristics of the snatch lift across varied lifting intensities. Our research variables included peak moment powers about the joints of the lower extremity, bilateral shoulder symmetry, and range of anterior-posterior system centre of mass (COM) movement as barbell load was varied across 80, 85, and 90% of each lifter's maximum. The five subjects were elite-level Olympic weightlifters (mean age 23 +/- 4.18 years, mean mass 77.6 +/- 5.81 kg). Multiple dependent t-tests (one for each joint pair) with Bonferroni corrections were applied between left and right peak powers to assess symmetry in the lower extremities. No significant differences were found, t(df =14) = 0.068, 0.038, and 0.039. Significance statistics wereall > p (alpha/n) = 0.0167 about the ankle, knee, and hip joint pairs, respectively. This confirmed assumptions of previous researchers that peak moment powers in elite-level lifters were symmetrical between joint pairs of the lower extremity. Exploiting the symmetry results, we simplified further analyses by considering only the left side of the body. Repeated-measures ANOVA revealed no significant differences in average peak moment power in three dimensions about the joints of the left lower extremity across barbell intensities. In the flexion extension plane of motion, left ankle F (2, 8) = 2.594, p = 0.135, knee F (2,8) = 0.133, p = 0.878, and hip F (2, 8) = 0.420, P = 0.671). Similar results followed for motion about the y and z axes of motion. Results indicated between 80-90% of maximal barbell load, no differences existed in average peak moment powers about the joints of the lower extremity. These results confirmed the findings of Enoka (1988) and showed lifters do not accommodated heavier barbell loads through increased peak moment powers in the lower extremities.
Shoulder symmetry was assessed through graphical and numerical methods. All trials showed Pearson's correlations of r > 0.95, which indicated strong similarity between left and right shoulder trajectories. Bilateral shoulder position remained highly stable across barbell intensities, as participants did not modify shoulder symmetry across the tested intensity range. Range of anterior-posterior system COM movement showed no significant differences across barbell intensities (F (2, 4) = 0.765, P = 0.523). While the range of anterior-posterior system COM motion did not vary across barbell intensities, various motion trends were observed. The anterior-posterior range of system COM motion was quite small, but perturbations in system COM trajectory could be detrimental to subsequent lift phases as the barbell load approaches maximum.
In conclusion, peak moment powers about the joints of lower extremities did not vary significantly across snatch lifts of 80-90% maximal capacity. Thus, training programs designed to improve athletic power through the use of weightlifting movements should not exceed the 80% limit for snatch based exercises. Statistical tests revealed no significant differences between average peak moment powers between left and right joint pairs of the lower extremities. The peak moment powers during the snatch lift were not asymmetrical. Our research demonstrated elite-level weightlifters exhibiting strong linear correlation in shoulder position across the 8090% range of barbell loads. System COM showed no significant variation in anterior-posterior range of motion across barbell intensities. This research confirmed the results previously established by Enoka (1988) regarding power response to load variation.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/28860 |
| Date | January 2010 |
| Creators | Saxby, David John |
| Publisher | University of Ottawa (Canada) |
| Source Sets | Université d’Ottawa |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 99 p. |
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