Quantifcation of Physical Loading, Energy Intake and Expenditure In English Premier League Soccer Players
The physical demands of soccer match play have been extensively studied. Muscle glycogen is the major energy source required to meet these demands and strategies to maximise this provide clear performance benefits to match play. Such information has allowed sports nutritionists to develop specific guidelines to optimise physical performance and recovery. However, the physical demands of soccer training have only recently started to be examined. For this reason, Study 1 quantified training load in English Premier League soccer players (n=12) during one, two and three game weekly micro-cycles of the 2013-2014 season. Study 1 identified soccer training being significantly less than match play and identified that soccer training displayed evidence of training periodisation. Having identified typical training load during the weekly micro-cycle, it was recognised that soccer match play comprises a large portion of the weekly physical load. Accordingly, Study 2 quantified differences in season long physical load (inclusive of both training and match play) between players who were classified as starters (n=8, started ≥60% of games), fringe players (n=7, started 30-60% of games) and non-starters (n=4, started <30% of games). Study 2 identified that unlike total seasonal volume of training (i.e. total distance and duration), seasonal high-intensity loading patterns are dependent on players’ match starting status thereby having potential implications for training programme design and prescription of player-specific nutritional guidelines. Additionally, daily energy expenditures (EE) and energy intakes (EI) of elite players are also not currently known. Therefore, studies 3, 4 and 5 quantified EE and EI in English Premier League soccer players consisting of outfield positions (n=6), a professional GK (n=1) and a player undergoing a rehabilitation period from an ACL reconstruction (n=1), respectively. Studies 3 and 4 were conducted over a 7-day period of the 2015-2016 season, consisting of two match days (MD) and five training days (TD). Study 5 consisted of six training days and one day off. Studies 3 and 4 identified CHO periodisation strategies employed by English Premier League Players such that CHO intake was greater on MD than TD. Additionally, players readily achieve current guidelines for daily protein and fat intakes, although energy and macronutrient intakes are skewed on TD. Study 4 also identified that the GK exceeded average daily EE with EI although he failed to meet current recommendations for meals on MD. In study 5 the player was operating in an energy deficit and he was able to decrease his total body mass in the initial 1-6 weeks post injury, which was attributable to largely fat loss. In summary, the work undertaken in this thesis has quantified the typical physical loading patterns of professional soccer players according to fixture schedule, starting status and in special populations. Additionally, the quantification of EI and EE (using DLW) also provides the first report of EE in elite soccer players from the English Premier League. When taken together, these data therefore provide a theoretical framework for soccer-specific nutritional guidelines especially in relation to the concept of nutritional (specifically, carbohydrate) periodisation. Further studies are now required to quantify the specific energy and CHO cost of habitual training sessions completed by elite soccer players as well as examining the manipulation of CHO availability on soccer-specific training adaptations.
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