The aims of this thesis were to; firstly, address the numerous concerns for athletes associated with exercise-induced dehydration and electrolyte loss; secondly, to examine the development of methods of assessing soccer players’ performance; and thirdly, to investigate the inter-relationship between soccer-specific tests. Finally, through a series of studies, the effect of electrolyte loss on subsequent soccer-specific performance was examined. / Chapters 1 and 2 comprise of detailed literature reviews, which introduce the pertinent issues related to hydration, electrolyte loss and assessment of soccer performance and outline areas of necessary future research. Chapter 3 measured the effect of short-term fatigue, through a repeated sprint ability (RSA) test, on subsequent skill performance, via the Loughborough Soccer Passing Test (LSPT), in thirty international level female soccer players. No significant differences were observed in any of the movement, penalty or total time taken to complete the LSPT between the pre- and post-RSA scores. / Chapter 4 investigated the hydration status and electrolyte loss of 14 professional soccer players (mean ± SD; Age: 24.1 ± 3.5 years; Height: 1.78 ± 0.07 m, Body mass (BM): 72.6 ± 12.1 kg) during normal “in-season” training and subsequently examined the effect of beverage sodium (Na⁺) on RSA performance. It was found that RSA performance was significantly improved in professional soccer players by the inclusion of 21.32 mmol·L⁻¹ Na⁺ in a beverage, when compared to a control beverage. / Chapter 5 examined the effects of 60 min of soccer-specific training on LSPT performance, hydration status and core temperature (Tc) when ingesting either a carbohydrate-electrolyte (CHO-E) or control (CON) drink. Seven healthy male soccer players (age: 23 ± 2.9 y, height: 1.7 ± 0.04 m, mass: 62.7 ± 6.7 kg) each completed a carbohydrate-electrolyte (CHO-E) and a control (CON) trial. There was an improvement in movement time (p = .034) and overall LSPT performance (p = .031) post-exercise in CHO-E when compared with CON. No differences were observed in Tc or absolute and relative body mass loss between trials (p> .05). / The final investigation of this thesis is detailed in chapter 6, where the purpose of the investigation was to examine the effect of beverages with different Na⁺ concentrations in soccer players on repeated sprint and soccer skill performance during and after soccer-simulated activity in a hot and humid environment. 12 healthy, male, semi-professional soccer players volunteered for this study (mean ± SD: age 24.5 ± 3.3 y, height 1.8 ± 0.06 m, BM 78.1 ± 9.4 kg). The results highlighted that the RSA performance was improved in both the High-Na⁺ and Na⁺ trials when compared to the CON trial at each time point (p < 0.05). A significant improvement in LSPT performance was observed in the Hi-Na⁺ trial compared with CON trial at all measurement time points (p < 0.05). / The findings from this thesis highlight that the addition of Na⁺ to a beverage can enhance sprint and skill performance in soccer players when the beverage is consumed during sport-specific training in a hot and humid environment. / 本論文的研究目的包括; 首先，探討運動員在運動時脫水和流失電解質的眾多顧慮;其次，考究足球員表現評估方法之發展; 第三，通過一系列的研究，調查電解質流失對隨後足球專項表現的影響。最後，就不同足球專項評估方法的相互關連性進行研究。 / 第1章和第2章包含詳盡的文獻綜述，當中介紹了水合作用、電解質流失和足球員表現評估方法的議題，並帶出未來需要研究的方向。第3章探討透過反复衝刺能力（ RSA ）測試引致的短期疲勞對足球表現的影響。30名國際級女子足球運動員在短期疲勞前後進行LSPT技術測試。結果顯示，RSA前後的LSPT成績 (不論動作、懲罰或總完成時間)均無顯著差異。 / 第4章調查了14名專業足球運動員（平均值±標準差; 年齡： 24.1 ±3.5歲，身高：1.78 ±0.07米，體重（ BM ）：72.6 ±12.1千克）於”比賽季”常規訓練的水合狀態和電解質流失，並隨後研究飲料鈉（Na +）對RSA表現的影響。研究發現， 與對照組相比，運動員飲用包含21.32 mmol.L -1 Na +的飲料後，RSA表現有顯著提升。 / 第5章研究攝入碳水化合物-電解質飲料（ CHO - E）或對照飲料（CON ）後，60分鐘足球專項訓練對LSPT表現，水合狀態和核心溫度（Tc）的影響。七名健康男性足球員（年齡：23 ±2.9歲，高度： 1.7 ±0.04米，體重： 62.7 ±6.7千克）各完成一個碳水化合物-電解質（ CHO - E）和一個對照組（CON ）試驗。與CON組相比，，CHO - E組在運動時間（P = .034 ）和整體LSPT表現（P = .031 ）均有顯著提升。兩組間的Tc或絕對和相對體重流失則無顯著差異（P> 0.05 ）。 / 在最後第6章，本論文研究在高溫高濕環境下的足球模擬活動期間和隨後，不同Na +濃度飲料對足球員的反複衝刺和足球專項技巧表現的影響。 12名健康的男性半職業足球運動員自願參加本研究（平均值±標準差： 24.5 ±3.3歲，身高1.8 ±0.06米，體重78.1 ±9.4千克） 。結果顯示，與CON組相比，高Na +和Na +組在所有測量時間點中的RSA表現都有顯著提高（ P <0.05）。至於LSPT表現，高Na +組則比CON組在所有測量時間點均有顯著改善（ P < 0.05）。 / 綜上所述，本論文的研究結果強調，在飲料添加Na +可提高足球運動員在炎熱和潮濕的環境訓練時的短跑和技術表現。 / O'Reilly, John Timothy. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2014. / Includes bibliographical references (leaves 116-137). / Abstracts also in Chinese. / Title from PDF title page (viewed on 08, November, 2016). / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only.

Thesis (MScSportSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Talent identification and early selection into a professional soccer academy has been reported to be very important for the long term development of footballing expertise (Le Gall et al., 2010). This awareness of the need for early identification of gifted youngsters has led to an increased number of soccer centres of excellence and academies throughout the world. Traditionally, identification and selection of promising individuals into youth soccer academies has been linked to a coach’s subjectivity and preconceived image of the player. Once this method is used in isolation it can result in tedious misjudgements in talent identification - hence the emphasis on science-based approaches. Through soccer-specific research, a number of anthropometric and physical parameters have been linked to successful performance in soccer. The primary aims of the study were to explore the anthropometric, somatotype and functional fitness characteristics of young academy soccer in South Africa and Zimbabwe and to distinguish variables that can be relevant for Talent Identification. The study followed a quantitative non-intervention design with a sample of convenience. A total of 74 young soccer players (Age 15.9±0.81) from South African (n = 41) and Zimbabwean (n = 33) soccer academies were purposively sampled. The following anthropometric variables were measured following the International Society of the Advancement of Kinanthropometry (ISAK) protocol: body mass and height; skinfolds – (triceps, subscapular, biceps, iliac crest, supraspinale, abdominal, front thigh, medial calf); Girths – (arm relaxed, arm flexed and tensed, waist, gluteal, and calf); bone breadths – (biepicondylar humerus and biepicondylar femur). Functional fitness variables that were measured include: lower back muscle flexibility (sit and reach test), upper body flexibility (shoulder flexibility), leg power using (vertical and horizontal jumps), overhead throw (2kg medicine ball throw), speed tests (10, 20, and 40m sprint tests), agility (Illinois test) and aerobic fitness (Hoff test). There were no statistically significant differences in age, body mass, height, fat mass, body mass index, lower back flexibility, right shoulder flexibility, 20m sprint, and endurance capacity (p>0.05). Statistically significant differences were found in percentage body fat (p>0.05), sum of 8 skinfolds, fat free mass, somatotype, left shoulder flexibility, upper and lower body power, 10m and 40m sprints (p<0.01). South African players were found to have higher %BF and sum of skinfolds and then Zimbabwean players. It was concluded that Zimbabwean players performed significantly better than South Africans in agility, 10m, 40m sprints, vertical jump, horizontal jump and overhead throw and had better future chances of success in soccer. Goalkeepers were taller and heavier, while midfielders and defenders were found to be lighter and shorter. Goalkeepers were the most agile group, while forwards were the fastest group. Agility, power and speed were the most important variables that can be used during talent selection and coaches should purposefully work to develop these characteristic during training sessions. Height and weight are relevant in allocating positional roles to players and not in Talent Identification. / AFRIKAANSE OPSOMMING: Talentidentifisering en vroeë seleksie in ʼn professionele sokkerakademie blyk baie belangrik te wees vir die langtermyn ontwikkeling van sokker vaardighede (Le Gall et al., 2010). Hierdie behoefte vir die vroeë identifisering van talentvolle jong spelers het aanleiding gegee tot ʼn toename in sokker sentra van uitnemendheid en akademies wêreldwyd. Tradisioneel is die identifisering en seleksie van belowende individue vir toelating tot ʼn jeug sokker akademie aan ʼn afrigter se subjektiwiteit en voorafopgestelde idees van die speler gekoppel. Wanneer die metode in isolasie gebruik word kan dit dodelike mistastings in talent identifisering teweeg bring – daarom die klem op wetenskaplik gebaseerde benaderings. Deur sokker spesifieke navorsing is daar alreeds ʼn aantal antropometriese en fisieke parameters aan suksesvolle prestasie in sokker gekoppel. Die primêre doelwitte van die studie was om die antropometrie, somatotipe en funksionele fiksheidskenmerke van jong sokker akademie spelers in Suid-Afrika en Zimbabwe te ondersoek en om veranderlikes wat relevant vir talentidentifisering kan wees te onderskei. Die studie het ʼn kwantitatiewe, nie-intervensie ontwerp met ʼn gerieflikheidsteekproef gevolg. ʼn Totaal van 74 jong sokkerspelers van Suid-Afrika (n = 41) en Zimbabwe (n = 33) sokker akademies is doelgerig geselekteer (ouderdom 15.9 ± 0.81 jaar). Die volgende antropometriese veranderlikes is ooreenkomstig met die International Society of the Advancement of Kinanthropometry (ISAK) protokol gemeet: liggaamsmassa en -lengte; velvoue (triseps, subskapulêr, biseps, iliokristale vou, supraspinalis, abdominale, quadriseps, mediale gastroknemius); omtrekke (arm ontspanne, arm in fleksie en gespanne, middel, gluteale, en kuit); been breedtes (biepikondelêre humerus en biepikondelêre femur). Funksionele fiksheidsveranderlikes wat gemeet is was: laerug spierlenigheid (sit en reik toets), boonste ekstremiteit lenigheid (skouer lenigheid), beenkrag (vertikale en horisontale spronge), oorhoofse gooi (2kg medisyne balgooi), spoedtoets (10, 20, en 40m spoedtoetse), ratsheid (Illinois toets) en aërobiese fiksheid (Hoff toets). Geen statisties betekenisvolle verskille is in ouderdom, liggaamsmassa, -lengte, vetmassa, liggaamsmassa indeks, laerug lenigheid, regterskouer lenigheid, 20 meter spoed en uithouvermoë kapasiteit (p>0.05) tussen SA en Zimbabwe spelers gevind nie. Statisties betekenisvolle verskille is wel in persentasie liggaamsvet (p<0.05), som van agt velvoue, vetvrye massa, somatotipe, linkerskouer lenigheid, boonste en onderste ekstremiteit liggaamskrag, 10m en 40m spoed (p<0.01) gevind. Suid-Afrikaanse spelers het ʼn hoër persentasie liggaamvet en som van velvoue as die Zimbabwiese spelers gehad. Daar is tot die gevolgtrekking gekom dat Zimbabwiese spelers betekenisvol beter as Suid-Afrikaanse spelers in die meeste fiksheidstoetse gevaar het en waarskynlik beter kanse vir sukses in sokker het. Doelwagters was groter en swaarder, terwyl middelveld spelers en verdedigers ligter en korter was. Doelwagters was die ratste groep, terwyl voorspelers die vinnigste groep was. Ratsheid, krag en spoed is as die belangrikste veranderlikes geïdentifiseer wat tydens talentidentifisering gebruik kan word en afrigters moet doelbewus daaraan werk om hierdie eienskappe tydens oefensessies te ontwikkel. Lengte en gewig is relevant in die toekenning van posisionele rolle aan spelers en nie in talentidentifisering nie. Hierdie is die eerste studie waarin die antropometriese en funksionele fiksheidsprofiele van jong sokkerspelers in Suid-Afrika en Zimbabwe met mekaar vergelyk word. Dit baan die weg vir ander navorsers om hierop uit te brei deur sokkerspelers van ander lande in Afrika te toets en by te dra tot die kennis van sokkerspelers in Afrika. Hierdie navorsing skep ook die basis vir afrigters en oefenkundiges in Afrika om die bydrae wat die wetenskap maak ten opsigte van liggaamsamestelling en funksionele fiksheid beter te verstaan om talentidentifisering in sokker te verbeter.