Thesis (MEd)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: The purpose of the study was to compare the effectiveness of an aquatic- and landbased plyometric programme upon selected, sport-specific performance variables in adolescent male, rugby union players. A group of 52 rugby players (age: 16.3 ± 0.8 years, height: 176 ± 6.9 cm and body mass: 76.1 ± 11.9 kg) were randomly assigned to one of three groups: aquatic group (n=18), land group (n=17), and a control group (n=17). Prior to and after the sevenweeks of training, the power, agility and speed of participants were assessed by means of Fitrodyne repeated countermovement jumps, the Sergeant vertical jump, the Illinois agility test, a standing broad jump, and a 10- and 40- metre sprint. All three groups maintained their summer extra-curricular sport commitments during the intervention period. When the three groups were analysed, no significant differences were found between the groups with regard to all tested performance variables. With regard to withingroup changes, the aquatic group improved significantly (p<0.05) in the Illinois agility test, performed to the right. The land group showed significant (p<0.05) improvements in peak concentric power during Fitrodyne repeated countermovement jumps. All groups reflected highly significant (p<0.01) improvements in the Sergeant vertical jump. None of the groups displayed any improvements in sprint speed. The control was the only group to improve significantly in the standing broad jump (p<0.05). Land-based plyometric training might be a functionally superior training modality for athletes, although aquatic plyometrics could also offer an effective training modality for performance enhancement in power-based sports such as rugby union football. Aquatic-based plyometrics should not completely replace land-based plyometrics, as it might not adequately develop the specific neuromuscular patterns or functional needs of explosive sports. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die effektiwiteit van ‘n water- en landgebaseerde pliometriese program met mekaar te vergelyk in terme van geselekteerde, sportspesifieke uitvoeringsveranderlikes in manlike adolessente rugbyspelers. ‘n Groep van 52 rugbyspelers (ouderdom: 16.3 ± 0.8 jaar, lengte: 176 ± 6.9 cm en liggaamsmassa: 76.1 ± 11.9 kg) is lukraak in een van drie groepe ingedeel: watergroep (n=18), landgroep (n=17), en ‘n kontrolegroep (n=17). Voor en na die sewe-weke oefenprogram, is spelers se plofkrag, ratsheid en spoed getoets deur middel van Fitrodyne herhaalde spronge, Sergeant vertikale sprong, Illinois ratsheidstoets, staande verspring, en ‘n 10- en 40-m spoedtoets. Al drie groepe het vir die duur van die intervensieperiode met hulle somersport aangegaan. Na analise van die drie groepe se data, is daar geen statisties betekenisvolle verskille tussen die groepe ten opsigte van die prestasieveranderlikes gevind nie. Die waterpliometriese groep se prestasie in die Illinois ratsheidstoets na regs het statisties beduidend (p<0.05) verbeter. Die landgroep het betekenisvolle (p<0.05) verbetering in die piek konsentriese plofkrag met die Fitrodyne herhaalde spronge getoon. Aldrie groepe het betekenisvolle (p<0.01) verbetering getoon in die Sergeant vertikale sprong. Geen groep se spoed het verbeter nie. Slegs die kontrolegroep se staande verspring het statisties betekenisvol verbeter. Land-gebaseerde pliometriese oefening kan moontlik, vanuit ‘n funksionele oogpunt, ‘n beter oefenmodaliteit vir atlete wees. Watergebaseerde pliometriese oefening kan egter ook ‘n oefenmodaliteit vir sport wat plofkrag vereis, soos rugby, wees. Watergebaseerde pliometriese oefening behoort nie land-gebaseerde pliometriese oefening te vervang nie, omdat dit moontlik nie aan die spesifieke neuromuskulêre patrone en funksionele behoeftes van eksplosiewe sport voldoen nie.