Biomechanical evaluation of jumping: the role of laterality, arm swing, muscle contraction mode and movement direction

U ovoj su disertaciji istraživane vrijednosti u kinetičkim varijablama koje opisuju pojedine vrste skokova klasificirane s obzirom na sljedeće zadane kriterije: smjer kretanja, lateralnost, korištenje zamaha rukama i režim mišićnog rada. Cilj je bio utvrditi hoće li se grupe skokova klasificirane na temelju zadanih kriterija značajno razlikovati u kinetičkim varijablama koje se odnose na vrijednosti vršne sile reakcije podloge, vršnog gradijenta sile i impulsa sile. Uzorak ispitanika činilo je osmero hrvatskih atletičara (5 muških i 3 žene) od kojih se šestero bavi skakačkim, a dvoje sprinterskim atletskim disciplinama. Ispitanici su bili ili su trenutno aktualni članovi hrvatske nacionalne atletske selekcije s iskustvom nastupanja na brojnim i velikim međunarodnim natjecanjima. Prosječna dob ispitanika za vrijeme mjerenja iznosila je 28,1 godinu, prosječna visina tijela 1,77 m dok je prosječna masa tijela iznosila 72,8 kg.Ispitanici su tijekom mjerenja izveli 159 različitih vrsta skokova. No, ukupan broj skakačkih entiteta u obradi podataka je bio 195 zbog normaliziranja opterećenja po jednoj nozi. Na taj se način broj entiteta povećao za 36 zbog zasebnih i različitih rezultata prednje i stražnje noge kod bilateralnih asimetričnih skokova te unutrašnje i vanjske noge kod bilateralnih skokova s promjenama smjera. Zbog toga se mjerenje provodilo uz pomoć dvije platforme za mjerenje sile reakcije podloge.Rezultati su potvrdili postavljenu temeljnu istraživačku hipotezu za svaki od korištenih kriterija klasifikacije skokova. Konkretno, kinetičke varijable izvedene iz sile reakcije podloge statistički značajno razlikuju pojedine skupine skokova, klasificirane temeljem odabranih kriterija. Ispostavilo se da svaka od jedanaest istraživanih kinetičkih varijabli može značajno razlikovati skupine skokova u barem jednom od odabranih kriterija. Varijable vršne sile reakcije podloge, vršnog gradijenta sile i impulsa sile imaju prethodno dokazanu visoku pouzdanost te ovi nalazi potvrđuju važnost i korisnost primjene kinetičkih varijabli sile reakcije podloge u opisivanju, vrjednovanju i klasifikaciji skakačkih sadržaja. Rezultati ove studije ukazuju da bi se klasifikacija skokova po intenzitetu ubuduće trebala fokusirati na temelju dva kinetička kriterija: vršna sila reakcije podloge i vršni gradijent sile. Te dvije mjere zajednički najbolje opisuju intenzitet skokova. S praktičnog stajališta, rezultati ove studije pokazuju da je prilikom odabira skokova na temelju intenziteta potrebno voditi računa o vršnoj sili reakcije podloge u kombinaciji sa vršnim gradijentom sile. No, osim toga, vrlo je važno i poznavanje modaliteta izvedbe skokova (lateralnost, zamah rukama, režim mišićnog rada, smjer kretanja, vrsta kontakta stopala s podlogom). S praktičnog stajališta u smislu prevencije od ozljeda, ovo istraživanje je utvrdilo da se skokovi sa cik-cak promjenama smjera te lateralni skokovi u kretanju mogu smatrati vrlo rizičnim.Informacije iz ovog istraživanja će pomoći u kreiranju programa koji su specifični prema pojedinim sportskim aktivnostima, cilju rehabilitacijskog procesa, prevenciji ozljeda i metodici poučavanja skakanja kod mlađih sportaša. Razlikovanje i rangiranje grupa skokova uz pomoć kinetičkog pristupa i prema odabranim kriterijima zasigurno mogu pomoći u praksi.In this dissertation, we investigated the values of the kinetic variables that describe various types of jumps, classified according to the following criteria: direction of movement, laterality, use of the arm swing, and the type of a muscle action. The aim was to determine if the groups of jumps classified according to the set criteria would be significantly different in terms of the observed kinetic variables, specifically, the ground reaction force, the peak force gradient, and the impulse. The sample consisted of eight Croatian track and field athletes (5 males and 3 females) out of which six competed in jumping events and the remaining two competed in sprinting events. The participants were current or former members of the Croatian national track and field team and had a history of competing in numerous international track and field competitions. The average age of the participants at the time of the study was 28,1 years, their average height was 1,77 m, and their average body mass amounted to 72,8 kg.The participants performed a total of 159 various types of jumps. However, the total number of entities in data processing was 195, due to the load normalization to a single leg. In this way, the number of entities increased by 36 due to the individual results of forward and backward leg in bilateral asymmetrical jumps as well as inner and outer leg in bilateral jumps that included change of direction. This is the reason all the measurements in the study were performed using two force platforms.The results confirmed the main research hypothesis for each of the criteria used to classify jumps. Specifically, kinetic variables derived from the ground reaction force were statistically significant in discriminating the various types of jumps classified according to the chosen criteria. We noticed that each of the eleven observed variables could significantly discriminate groups of jumps in at least one of the chosen criteria. Variables corresponding to peak ground reaction force, peak force gradient as well as impulse had all been previously shown to exhibit high reliability, and these findings confirm the importance and usefulness of the application of kinetic ground reaction force variables in description, evaluation and classification of various jumping techniques. The results of this study point toward the fact that the classification of jumps, according to intensity, should in the future focus on two main kinetic criteria: (a) peak ground reaction8force, and (b) peak force gradient. Taken together, these two variables proved to be the best descriptors of the intensity of a jump. In practical terms, the results of this study point toward the fact that, when selecting jumps according to intensity, it is necessary to take into account peak ground reaction force in combination with peak force gradient. However, it is also very important to be familiar with the modality of the execution of a jump (i.e. laterality, arm swing, type of muscle action, movement direction, type of contact with the ground). In practical terms, and with regard to injury prevention, this research has determined that the jumps that include a zig-zag change of direction as well as lateral jumps in motion may be considered to pose a high injury risk.The findings of this study may help in devising training regimens that are specific according to a sports activity, the aim of a rehabilitation treatment, injury prevention as well as jumping skill acquisition in young athletes. Discrimination and classification of groups of jumps according to the kinetic approach as well as chosen parameters could certainly be helpful in the real-world setting of applied kinesiology