Does counter-movement effect jump performance and does using the arms further this improvement when performing a vertical jump?
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Does counter-movement effect jump performance and does using the arms further this improvement when performing a vertical jump? Introduction: Vertical jumping contributes to performance in almost all sports, obviously some sports such as basketball use it a lot more that other sports such as tennis. When performing a motor task such as jumping, human beings typically start with countermovement (CM), CM can be described as a quick bend of the knees during which the body's centre of mass drops before being propelled upwards (Harman et al, 1990). There is evidence to support that task performance is improved with CM, for instance, it has been shown that subjects achieve a greater jump height with CM than without. This is because subjects are able to produce more work and/or use the work more effectively in a countermovement jump (CMJ) than a non-CMJ (Bobbert et al, 1996). Researchers to date have proposed different theories as to why CM has a positive effect on vertical jump performance. Enoka (1988) cited in Harman (1990) proposed the performance enhancing effects of the countermovement is that concentric contraction immediately following an eccentric stretch begins with the muscle already under considerable tension, making more chemical energy available for generation of force. A later study conducted by Harman et al (1990)
VJ no CM 0.271 0.006 2.306 0.026 141.055 1.573 c. VJ leg only + CM 0.562 0.730 -0.846 3.707 -51.733 226.701 d. UBM straight legs 0.024 0.047 -0.302 0.713 -18.480 43.600 Graphs of Mean Results Subject 1 (mean results) Subject 2 (mean results) Figure 1. Max flight height means for Subject 1 Figure 2. Max flight means for Subject 2 Figure 3. Take off Velocity means for Subject 1 Figure 4. Take off Velocity means for Subject 2 Figure 5. Vertical Impulse means for Subject 1 Figure 6. Vertical Impulse Means for Subject 2 Discussion: The results collected for subject 1 was to be expected (see table 1); the subject-performed best in jump a, using CM and arms. This was hypothesised by the writer and supported by numerous researchers, research has concluded that jumping performance can be greatly improved with CM and arms compared to without (Bobbert et al, 1996; Enoka 1988; Harman et al, 1990; Payne 1968; Lees et al, 2004 and Bishop et al, 2004). When comparing jump a (using CM and arms) to jump b (using no-CM) there is a 15% improvement in overall jumping performance in jump a (see table 1). This is supported by Bobbert et al (1996) who found CMJ's produced greater jump heights than non-CMJ's.
The participants had not undergone any training prior to completing the study, which could account for the inaccuracy of results produced by subject 2. Prior to completing the study, the participants were not given proper protocols to warm up, this may have subsided the subjects' true performance potentials, Hunter and Marshall (2002) found that flexibility had a positive effect on jump performance. With the performers not properly warmed up the subjects' flexibility would have been limited as a result. Overall, subject 1 confirmed the writer's hypothesis and met the aims of the study, providing evidence that CM increased vertical jump performance, and CM with the use of arms increased vertical jump performance further. Subject 2 did not confirm the writers hypothesis or meet the aims of the study, however, subject 2 has provided a learning curve for future study, providing evidence that recording data correctly and following strict protocols should remain essential when completing further testing. If the experiment were to be repeated 'controls' would have to be enforced to achieve more valid results. A sheet for recording personal details, such as height and weight should be included, reducing the risk of error when obtaining results. More observers could be used to determine whether jumps were performed correctly, and it not being validated till all of them were agreed.
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