Force and velocity jump characteristics of University-level field hockey players

Van Jaarsveld, Amori (2020-12)

Thesis (MA)--Stellenbosch University, 2021.

Thesis

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.

AFRIKAANSE OPSOMMING: Daar word reeds jare lank navorsing gedoen oor sprong toetsing. Daar is egter geen studies wat rapporteer oor die verskille tussen die konsentriese fases van die teenbewegingsprong (CMJ) en die hurk sprong (SQJ) nie. Die doel van hierdie studie was eerstens om te bepaal wat die verskille is in die konsentriese fases van krag-, drywing-, en snelheid-tyd kurwes van die CMJ en SQJ. Tweedens het die studie beoog om te bepaal wat die verskil in hoogte is tussen CMJ en SQJ. Laastens het die studie beoog om vas te stel of die styfheid sprong (STJ) tempo van krag ontwikkeling gebruik kan word as prestasie aanwyser vir CMJ en SQJ. Drie-en-twintig (n = 23) universiteit veld hokkie spelers (n = 10 vroulik (F) en n = 13 manlik (M); ouderdom = 22 ± 1 jaar (F) en 21 ± 2 jaar (M)) het vrywillig aangebied om aan hierdie studie deel te neem. Spring toetse is uitgevoer op ‘n Bertec trapmeul (Bertec, USA) teen ‘n frekwensie van 3000 Hz. Data is opgeneem met die Noraxon® MR3.14.52 sagteware (Noraxon, USA). Die deelnemer se liggaamsmassa is gemeet met ‘n Bertec krag plaat, tot die naaste 0.1 kg. Elke deelnemer het drie pogings aangewend van die CMJ en SQJ. Die beste poging van die drie spronge is geanaliseer via statistiese parameter kartering (SPM).Statistiese parameter kartering (SPM) is gebruik om die verskille tussen die CMJ en SQJ se konsentriese fase krag-, snelheid-, drywing- en verplasing-tyd kurwes te bepaal. Die analise is uitgevoer deur die MATLAB R2020a (Weergawe 9.6) te gebruik. Die SPM algoritme het die statistiek veld oor die hele kurwe uitgewerk deur die kritiese toetsstatistiek drempel te korrigeer deur gebruik te maak van die egaligheid van die data, die data grootte en die ewekansige -veld gedrag. SPM normaliseer data tot 100% van die beweging wat geanaliseer is. Daarvolgens is resultate as persentasie waardes geïnterpreteer. SQJ se netto impuls berekeninge is aangepas om die stilste punt voor die aanvang van die konsentriese fase op te spoor. Resultate is in die artikel deurgegee in Hoofstuk Vier. ‘n Statisties beduidende verskil is waargeneem tussen 0- en 40% van die krag-, drywing- en snelheid-tyd kurwes vir CMJ en SQJ. Beskrywende data analise wys ‘n beduidende verskil in die relatiewe gemiddelde- en piek krag, opstygsnelheid, gemiddelde krag tussen en hoogte vir die twee spronge (p < 0.05). Daar is egter ‘n nie-statisties betekenisvolle verskil gevind in die relatiewe piek krag (p > 0.05) nie. vi Die eerste nul hipotese (H0) is verwerp, aangesien beduidende verskille gevind is tussen CMJ en SQJ krag-, drywing -, en snelheid-tyd kurwes van 0-70% van die konsentriese fase. Die tweede nul hipotese (H0) is ook verwerp aangesien beduidende verskille gevind is in die CMJ en SQJ prestasie veranderlikes. Laastens, die derde nul hipotese (H0) is verwerp weens gemiddelde en sterk korrelasies tussen die styfheid sprong tempo van krag ontwikkeling in prestasie van CMJ en SQJ. Ten slotte, daar is gevind dat die eksentriese belading ‘n invloed het op die konsentriese fasevan die CMJ aangesien ‘n beduidende verskil gevind is tussen 0-40% van die krag-tyd kurwe. Verder, ‘n statisties beduidende verskil is gevind in die aanvang (0-75%) konsentriese fase van die CMJ en SQJ deur die SPM analise te gebruik. Daar is egter ‘n nie-statisties beduidende verskil waargeneem van 70-100% van die konsentriese fase wat voorstel dat soortgelyke prestasie uitkomste vir CMJ en SQJ geld. Beskrywende data analise wys nie-statisties beduidende verskille in piek krag. Daar is egter statisties beduidende verskille gevind tussen die gemiddelde en piek krag, gemiddelde drywing, opstygsnelheid en sprong hoogte. Meer aandag moet dus gefokus word op die meganismes van bereiking van prestasie uitkomste, eerder as om te fokus op piek prestasie alleenlik.Die beperkings van die huidige studie was eerstens dat geen kinematiese data versamel is nie. Tweedens, die studie het staat gemaak op eenmalige toetsing. Laastens, manlike en vroulike data was saamgegooi. Toekomstige navorsing behoort kinematiese data in te sluit vir ‘n omvattende oorsig van ‘n atleet se prestasie. Verder, toekomstige navorsing moet toetsing versprei oor ‘n geperiodiseerde oefenprogram of oor ‘n volledige kompetisie seisoen. Toekomstige navorsing moet die verskille in die konsentriese fase van CMJ en SQJ tussen manlike en vroulike atlete ondersoek.

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