Characterisation of running specific prostheses and its effect on sprinting performance

Grobler, Lara (2015-12)

Thesis (PhD)--Stellenbosch University, 2015.

Thesis

ENGLISH ABSTRACT: The development of the running specific prosthetic (RSP) has allowed athletes with lower limb amputations to participate at a high level in sports such as sprinting. Literature regarding mechanical properties of RSPs and their influence on the athlete’s performance, on the other hand, is limited. This makes prosthetic selection a difficult task. The aim of this study was to assess the biomechanical and physiological effects of the mechanical characteristics of different RSPs on an athlete’s sprinting performance. The sprint performances of athletes with lower limb amputations were described in a retrospective analysis of Olympic and Paralympic times between 1992 and 2012, in an attempt to assess whether the technological advances in RSPs is evident. A 14 – 26% performance improvement was found for the T42 and T44 classes of the 100 and 200 m during this time in comparison to 2.2 – 2.8% for the Olympic athlete performances. These results were further supported by the lower competition density found in the amputee groups (Olympic 23.90 and 9.29 competitors.s-1; T42 4.53 and 1.93 competitors.s-1). It was therefore proposed that technology played a significant role in the performance progression of these athletes over the last 20 years. Differences in the characteristics of two RSP models (model E and X) were investigated. This was achieved by athlete independent mechanical testing during which the RSPs were dropped from a height of 30 cm and left to bounce on a force platform. The results revealed differences in the peak ground reaction force (GRFpeak) (model E > model X; p < 0.05) and maximal RSP compression (ΔL) (model X > model E; p < 0.05). This indicated that the RSP model E is more stiffness than the model X. These stiffness characteristics related to discrepancies in sprinting economy of an athlete completing four maximal anaerobic running tests (MART) using different RSPs. Two RSP stiffness categories of each model (Ecat4, Ecat6, Xcat4, Xcat6) were used for this testing and was randomly allocated to each testing session. It was found that the running speed at which the athlete attained a blood lactate concentration of 10 mmol.l-1 was the highest with the stiffest RSP (Ecat6), whereas it was the lowest in the softest RSP (Xcat4). Accordingly the lowest functional muscular fatigue as measured by a decrease in the pre and post-test counter movement jump height was found in this condition (Ecat6 7.35% vs. Xcat4 24.43%). From these investigations it was clear that technology is an important factor in the performances of amputee sprint athletes. Therefore prosthetic selection is of the utmost importance. Differences in the mechanical characteristics of the RSPs influence the sprint physiology and biomechanics and should therefore be taken into consideration when selecting a RSP.

AFRIKAANSE OPSOMMING: Die ontwikkeling van hardloop-spesifieke prostese (In Engels, running specific prosthetic, RSP) laat atlete met onderste ledemaat amputasies toe om op ‘n hoë vlak aan sportsoorte soos naellope deel te neem. Slegs beperkte literatuur aangaande die meganiese eienskappe van RSPs en die invloed daarvan op prestasie is beskikbaar. Die doel van die studie was om die effek van verskillende meganiese eienskappe op die biomeganiese en fisiologiese prestasie van ‘n atleet te evalueer. In ‘n retrospektiewe analise van die Olimpiese en Paralimpiese resultate in die 100 en 200 m tussen 1992 en 2012 is die invloed van tegnologiese vooruitgang op atlete met onderste ledemaat amputasies ondersoek. ‘n Prestasie verbetering van tussen 14 en 26% vir die 100 en 200 m van T42 en T44 atlete is gevind. In vergelyking hiermee het die Olimpiese prestasie met slegs 2.2 – 2.8% verbeter. Hierdie bevinding word verder gestaaf deur die laer kompetisie digtheid in die geamputeerde groepe (Olimpies 23.90 en 9.29 deelnemers.s- 1; T42 4.53 en 1.93 deelnemers.s-1). Gevolglik kan dit afgelei word dat tegnologie ‘n betekenisvolle uitwerking op die prestasie verbetering van hierdie atlete het. Ondersoek is verder ingestel op die verskillende karaktereienskappe van twee RSP modelle (model E en X). Dit was uitgevoer deur middel van atleet-onafhanklike meganiese toetse. Tydens hierdie toetsing is die RSP van ‘n 30 cm hoogte laat val en toegelaat om vrylik op ‘n kragplatform te hop. Die resultate het getoon dat verskille tussen die piek grond reaksiekrag (In Engels, peak ground reaction force, GRFpeak) (model E > model X; p < 0.05) en maksimale RSP kompressie (ΔL) (model X > model E; p < 0.05). Hierdie resultate dui daarop dat die RSP model E groter styfheid as model X gehad het. Hierdie styfheid karaktereienskappe het verband gehou met die variasie in die naelloop ekonomie van ‘n atleet wat vier maksimale anaërobiese hardlooptoetse (MART) met verskillende RSPs voltooi het. Vir die toetsing is twee styfheid kategorieë RSPs van elke model gebruik (Ecat4, Ecat6, Xcat4, Xcat6). Hierdie RSPs is lukraak aan die atleet vir elke toets toegeken. Die hardloopspoed waarteen die atleet ‘n bloedlaktaat konsentrasie van 10 mmol.l-1 bereik het, was die hoogste met die styfste RSP (Ecat6), teenoor die laagste spoed wat gevind is in die mees buigbare RSP (Xcat4). Dienooreenkomstig was die laagste funksionele spiervermoeïenis, soos gemeet deur ‘n afname in die voor en na toets teenbeweging sprong (In Engels, counter movement jump, CMJ), ook gevind met die gebruik van die styfste RSP (Ecat6 7.35% vs. Xcat4 24.43%). Dit was duidelik dat tegnologie ‘n belangrike rol speel in naellope vir atlete met amputasies. Hierdie resultate toon die belangrikheid van prostese keuse. Verskille in die meganiese eienskappe van die RSPs beïnvloed beide die fisiologiese en biomeganiese response tydens die naelloop en moet gevolglik in ag geneem word wanneer ‘n RSP gekies word.

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