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FUELLING FOR THE WORK REQUIRED IN PROFESSIONAL FOOTBALL: A THEORETICAL MODEL FOR CARBOHYDRATE PERIODISATION FEATURE / DR LIAM ANDERSON Introduction Professional football clubs are continuously posed with new questions that can often be answered through research and development. Whilst it is important to stay in tune with current literature to help answer these questions, it is also important to ask and answer questions that are specific to individual environments (i.e., players, management styles, training times, operating restrictions etc.). Going back almost 10 years, the questions we had before embarking on this research were “how much do these players need to eat each day?” and “what does players nutritional intake look like in comparison to recommended guidelines?”. We set about performing numerous investigations into the physical loading, energy expenditure and energy intake of professional football players with the end goal of being to provide more sophisticated nutritional programmes to meet energy expenditure and facilitate improvements in performance, recovery, and fitness adaptations. Energy expenditure is a critical variable in human health and physiology 1, and implementing strategies to meet energy demands within elite football can be crucial for success and overall health of the player. Given that daily protein recommendations range from 1.6-2.2 g.kg-1 and recommended fat intakes equivalent to 30% energy intake 2, manipulation of carbohydrate intake would allow football players to meet differing daily energy demands. This type of periodised carbohydrate approach to sports nutrition has gained significant attention in endurance sports in recent years 3. Indeed, as part of answering the research questions mentioned above, our group and others have researched professional soccer players physical loading and energy requirements 2, 4-7 . These new findings have significantly altered the approach that performance practitioners follow when providing training and nutritional recommendations. The following article will summarise a theoretical model based off current scientific understanding of physical loading, energy expenditure and energy intake 8. This model, where carbohydrate is adjusted day-by-day and meal-by-meal according to the upcoming activity and the desired outcome of training sessions i.e., promoting exercise intensity vs stimulating metabolic adaptations, has been translated as a “fuel for the work required”
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Figure 1: Playing squad average total distance completed in training sessions and matches during two different 7-day testing periods. Figure A = one game week, Figure B = three game week (games played with <72 hours apart) Red bars = matches and green bars = training. MD = Match day. a denotes difference from day MD-4, b denotes difference from day MD-3, c denotes difference from day MD-2, d denotes difference from day MD-1 and e denotes difference from MD+2/ -1, all P < 0.05. Figure adapted and redrawn from Anderson et al. 4.
model. Although this is a model that can be implemented into many football clubs, it is important to tailor to the individual training structure and demands (i.e., morning training vs. evening training, high vs. low demands on different days etc.). Carbohydrate requirements for performance Match demands have been widely accepted by practitioners and academics since the 1970s 9. These demands have increased over time with distances covered at high-speed increasing ~30% from 2006-07 to 2012-13 in the English Premier League (EPL) and ~9% from 2012-13 to 2019-20 in the Spanish La Liga, heightening the importance of nutritional preparation for match play 10, 11. From a metabolic perspective,
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muscle glycogen is the major energy source to fuel these match demands. Krustup et al. 12 observed that pre-game muscle glycogen was 449 ± 23 mmol. kg-1 dry weight and decreased to 225 ± 23 mmol.kg-1 dry weight immediately after the match. This would suggest that there was sufficient glycogen available to continue exercising, however, analysis of individual muscle fibre (i.e., type IIa and IIx fibres) revealed that 50% of fibres could be classified as empty or almost empty. These fibres are responsible for sprinting and high-intensity activity. Therefore, muscle and liver glycogen are a potential contributing factor to fatigue and reduction in high intensity running towards the end of matches.
