Year: 2020
Type: dissertation
Abstract: ENGLISH ABSTRACT: Jump testing has been researched for many years. However, no studies have reported on the differences between the concentric phases of the countermovement jump (CMJ) and squat jump (SQJ). The aim of the study, firstly, was to determine the differences in the concentric phase force-, power-, and velocity-time curves of the CMJ and SQJ. Secondly, the study aimed to determine the differences between CMJ and SQJ jump performance variables. Lastly, this study aimed to establish whether rate of force development during the stiffness jump (SJ) could be used as a performance indicator for CMJ and SQJ jump performance. Twenty-three (n = 23) collegiate field hockey players (n = 10 female (F) and n = 13 male (M); age = 22 ± 1 years (F) and 21 ± 2 years (M)) volunteered to participate in this study. Jump tests were performed on a Bertec Instrumented treadmill (Bertec, USA) at a measurement frequency of 3000 Hz. Data were recorded using Noraxon® MR3.14.52 software (Noraxon, USA). The participant’s body mass was measured with a Bertec force plate, to the nearest 0.1 kg. Each participant performed three attempts of the CMJ and SQJ. The best of the three jumps were analysed. Statistical parametric mapping (SPM) was used to assess the differences between CMJ and SQJ concentric phase force-, velocity-, power-, and displacement-time curves. The analysis was performed using MATLAB R2020a (Version 9.6). The SPM algorithm calculated the statistic field across the whole curve by correcting the critical test statistic threshold using the smoothness of the data, the data size, and the random field behaviour. Data were normalised to 100% of the movement phase analysed. Therefore, results were interpreted in percentage value. SQJ net impulse calculations were adjusted to detect the stillest point prior to the initiations of the concentric phase. Research questions one and two were answered in Chapter Four. Results were reported in the article in Chapter Four. A statistically significant difference was observed between 0- and 40% of the force-, power, and velocity-time curves for CMJ and SQJ. Descriptive data analysis showed a significant difference in relative mean and peak force, take-off velocity, mean power between and jump height for the two jumps (p < 0.05). However, a non-statistically significant difference was found in relative peak power (p > 0.05). iv The first null hypothesis (H0) was rejected, as significant differences were discovered between CMJ and SQJ force-, power-, velocity-time curves during the concentric phase. The second null hypothesis (H0) was also rejected as a significant difference was found in CMJ and SQJ performance variables. Lastly, the third null hypothesis (H0) was rejected as moderate and strong correlations between SJ rate of force development and CMJ and SQJ performance outcomes. In conclusion, the eccentric loading has shown to influence the concentric phase of the CMJ as a significant difference was found between 0-40% of the force-time curve. Furthermore, statistically significant differences were found from the initiation up to 75% of the concentric phase of the CMJ and SQJ using SPM analysis. However, no statistically significant difference was observed from 70-100% of the concentric phase suggesting similar performance outcomes for CMJ and SQJ. Descriptive data analysis showed no statistically significant differences in peak power. However, statistically significant differences were found for mean and peak force, mean power, take-off velocity and jump height. Therefore, more attention should be focused on the mechanisms of achieving performance outcomes, rather than focussing on peak performance variables only. The limitations of the current study were firstly that that no kinematic data was collected. Secondly, the study relied on once-off testing. Lastly, data from men and women were pooled. Future research should include kinematic data for a comprehensive view of an athlete’s performance. Furthermore, future research should include testing throughout a periodised training program or an entire competitive season. Future research should further investigate the differences in the concentric phase of CMJ and SQJ between men and women.
Author: Amori Van Jaarsveld
Language: English
Subfield: Orthopedics and Sports Medicine
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W3164710806