In the afternoon, the third session of the conference focuses on hydration and fueling. The amount of water a player has in their body will depend upon their body size and body composition. Greater quantities of lean mass are associated with greater total body water. Thus, players body water content may range from approximately 30 L to 50 L, accounting for 55-70% of body mass respectively (Wang et al., 1999). The water content of the body in healthy players is well regulated (Raman et al., 2004). However, as players engage in football training and matches the rate of fluid turnover is significantly increased. This is because in both cool and hot environments, sweating provides the primary mechanism to dissipate the metabolic heat generated as a consequence of playing football (Ekblom 1986; Shirreffs et al., 2005). Sweat rates in footballers have been reported to range from 0.5 L·h-1 to 2.5 L·h-1 (Broad et al., 1996; Maughan et al., 2005; Shirreffs et al., 2005; Da Silva et al., 2012; Baker et al., 2016; Nuccio et al., 2017).
If we assume a higher level of total body water i.e. 50 L; in cool low intensity training environment total body would turn over in approximately 100 playing hours. However, during match play in warm environments, at a modest sweat rate of 1.5 L·h-1, total body water would turn over in approximately 33 playing hours. In practical terms, total body water would turn over in just under four weeks for a player completing 2-games a week and a 1 h training session between games. Thus, over a 38 week season a player’s total body water may turnover a conservative ten times.
Both acute and chronic hypohydration equivalent to deficit of >2-3% of pre-exercise body mass during exercise may increase cardiovascular strain (Armstrong et al., 1997), impair cognitive function (Ganio et al., 2011; Nuccio et al., 2017) and increase the perception of effort (McGregor et al., 1999). This may manifest as reduced physical (Mohr & Krustrup 2013) and technical (McGregor et al., 1999) football performance. To this end, after exercise players should aim to replace any fluid deficit (Maughan & Leiper 1995). Normal eating/drinking practices are, in general, sufficient to restore euhydration. However, during pre-season or periods of fixture congestion, rapid and complete rehydration can be achieved by drinking 1.5 L of a sodium-containing fluid for each 1 kg of a player’s body mass loss (Thomas et al., 2016). Strategies such as weighing players in and out of training allow individualised drinking plans to be developed and thus fluid turnover to be monitored (Maughan & Shirreffs 2008).
The brain is the vital, yet often forgotten about organ for football performance. Although player psychology is beyond the scope of this article, it is the brain which must convey space, make tactical decisions, regulate body processes and drive the recruitment of muscle to complete the physical movement required for football. Decision making and the ability to make the correct decision at high speed are likely key points of differentiation between elite players and their recreational counterparts.
There are clear reasons why there has been limited information regarding the brain tissue and rates of protein synthesis in vivo in humans. However, a recent study by Smeets and colleagues used stable isotope methods to directly assess brain protein synthesis rates in patients undergoing a temporal lobectomy (Smeets et al., 2018). Fascinatingly, brain tissue protein synthesis rates were 3-4-fold higher than skeletal muscle tissue, much higher than previously assumed. Accordingly, this hypothetically equates to the players brain being completely regenerated over a duration of 2 weeks. Therefore, players will, theoretically, have 20 “new” brains over a competitive season. This research is its infancy and the impact of diet and exercise, as well as the impact of football activity per se such as repeated heading of the ball, may have on brain protein turnover are yet to be established.
Based on the available literature firm nutritional guidelines to support brain protein remodelling cannot be made. Prudent advice would be to ensure the player maintains an adequate hydration status, especially if playing in the heat (see fluid section above) (Maughan et al., 2007) and protein intake (Phillips & Van Loon 2011). In addition various supplements may be considered, the main compounds presently under investigation and of interest are omega 3 fatty acids and creatine (Ashbaugh & McGrew 2016). This is because the ingestion of high dosages of omega 3 fatty acids may improve the short term outcomes following head injuries such as concussion (Lewis 2016). This may be achieved via neurite growth, increased neurite branching, and subsequent synaptogenesis, resulting in enhanced synaptic function and improved neuronal repair after a head injury (Kim & Spector 2013). Furthermore, the ingestion of omega 3 fatty acids has been reported to normalise levels of proteins associated with neuronal circuit function and locomotor control after sustaining a concussion (Wu et al., 2011). Supplementation with creatine monohydrate has been reported to improve cerebral energetics (Pan & Takahashi 2007; Turner et al., 2015). This may result in improved cognition, communication, self-care, personality, and behaviour (Sakellaris et al., 2006), all relevant to football performance and potentially brain remodelling (Sakellaris et al., 2008).
A footballer’s body is continuously rebuilding itself from the substrate provided via the diet. Thus, physically, the player that begins a season may be almost a completely different player by the end of the season. Observations from science highlight the important of appropriate practical nutrition strategies to optimize the remodeling of tissues to “recover” and “build” capable, resilient footballers.
*Disclaimer: Ian Rollo is an employee of the Gatorade Sports Science Institute, a division of PepsiCo, Inc. The views expressed in this article are those of the authors and do not necessarily reflect the position or policy of PepsiCo, Inc.
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