Female football players cover a distance of approximately 10 km during a match, using both aerobic (main source of energy for the body at rest and during low intensity activities) and anaerobic (intense physical activity obtaining energy in the absence of oxygen) energy systems.1, 2
This second type of high-intensity intermittent running causes a rise in core temperature3, and the subsequent thermoregulatory response involves an increase in skin blood flow and the onset of sweating due to evaporative heat loss3. High intensity running also results in marked glycogen depletion in both slow and fast twitch muscle fiber types4. Thus, the rise in temperature, together with muscle glycogen depletion, can precipitate fatigue. In football, this may explain to some extent the reduction in distance run and high-intensity running at the end of elite matches5, 6.
However, few studies have investigated fluid balance, carbohydrate intake, sweat rate and the amount of sodium in sweat during training and matches in elite female football players.
Knowledge of players’ carbohydrate intake during training and matches could help design strategies to improve performance, as it has been shown that suboptimal carbohydrate intake can affect football-specific performance7. In fact, consuming carbohydrates during training sessions that replicate match intensities may improve carbohydrate tolerance during competition, which could also reduce gastrointestinal discomfort8.
In this setting, the study Fluid Balance and Carbohydrate Intake of Elite Female Football Players during Training and Competition (Caroline A. Tarnow et al., 2022) was recently conducted. Its aim was to measure and compare sweat rate, sweat sodium, carbohydrate intake and fluid intake in elite female football players during a training session and a competitive match. This article summarizes their main characteristics, results and conclusions.
Key data from the study and main results
Nineteen elite female professional football players from the Futbol Club Barcelona first division team participated in the study9, which found the following outcomes:
The average sweating rate was significantly higher during the match compared to the training. As the environmental conditions and duration were similar during both, the difference is probably due to the higher exercise intensity of the match. In addition, it is also noted that competition may add additional anxiety and/or stress to the player, which may influence the sweating response10.
Quantity of sodium in sweat
No differences were found in the amount of sodium in sweat between the training
session and the match.
In contrast, large interindividual variations in the amount of sodium in sweat were
found in both the training session and the match.
Fluid intake was expected to be higher during the training session, as there was a greater opportunity to consume fluids compared to a match, where drinking is restricted to certain periods of time11. In contrast, fluid intake was not significantly different between the training session and the match.
Hydration status before exercise
Thirst scores were higher before training compared to the match. The data also showed that the degree of hypohydration during exercise may be underestimated since some players were already in a state of prior hypohydration.
In the present study, female soccer players ingested an average of 2.0 g-h-1 during the training session and 0.9 g-h-1 during the match, and opted for a 2% carbohydrate drink versus the 6% option.
However, for high-intensity intermittent exercise lasting >60 min, the recommended intake is 30 to 60 g-h-1 12,13.
Main conclusions of the study
The large interindividual variation in sweat rate and the amount of sodium in sweat during training and matches supports the need for individualized hydration recommendations. Thus, future research should be encouraged to record actual baseline measurements in reference to body mass, as well as other valid markers of hydration, to more accurately record actual hydration status14.
The players had more opportunities to consume carbohydrates during training, so the fact that intakes were low during the match and training suggests that this is due to preference rather than access or opportunity to ingest carbohydrates. And as noted, not meeting carbohydrate intake recommendations during training and matches could affect soccer-specific performance15-17.
Further research should explore why players self-selected low-carbohydrate options (i.e., 2% solution versus 6% solution) and did not adjust carbohydrate intake in response to changing exercise demands. Improved understanding and knowledge of carbohydrates among female soccer players, along with proper hydration education, should be an additional focus on sports nutrition for elite female soccer players.
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