A new article was published (1) with insights about sweat losses, and intake patterns of FC Barcelona players during different training sessions. Read the report below.
Sweat rates in Professional Soccer
Soccer is a game played with repeated bouts of very high intensity exercise. During parts of the season, heat stress will be considerable. Players will sweat a lot and hydration status is often monitored, because dehydration has been associated with players’ physiological capacity to compete, and also recovery from training and matches. Some studies have suggested that even moderate hypohydration (e.g., a 2% loss in body weight) may have a negative effect on physiological function and performance. Significant dehydration can result in a higher exercise heart rate, a higher plasma osmolality, a lower blood flow to the skin, and a higher core temperature. However, by drinking enough this can be prevented. There are also studies that show that carbohydrate intake (60-75g/h) can improve running performance, sprint performance, agility and other skill performance measurements (Read more here). A few studies have measured nutrition habits of elite soccer players and other studies have reported sweat rates. However, the data in elite soccer is scarce, especially in training settings.
What was the study?
Players of the men’s first team of Futbol Club (FC) Barcelona (Spanish first division; La Liga) participated in this study (14 in total). Their sweat response and their ad-libitum (voluntary) fluid and carbohydrate intake were recorded on four separate training days during the competitive season. This was a purely observational study, there was no advice or intervention. The days were selected to obtain measurements in different conditions: 2 measurements in cool conditions (15°C and 66% humidity) and 2 in warm conditions (29°C and 52% humidity). Two of the training sessions were low intensity. The other 2 were high intensity running. So, in total there were 4 different combinations:
Cool and low intensity
Cool and high intensity
Warm and low intensity
Warm and high intensity
(The details of how intensity was defined can be found in the paper but briefly: high intensity was 10-12 sprints and 191-232m high speed running and a total distance of 4.9km).
As expected, on average the players experienced a reduction in body mass that was relative to the intensity and heat stress. However, the individual differences were large. The intensity seemed a slightly more important factor than the temperature (at least in these ranges of intensity and temperature)
There are a few noteworthy findings in this study that will be discussed briefly below:
Players drank enough
Players adequately adjusted their fluid intake to prevent hypohydration greater than 2% of pre-exercise body mass. No player lost more than 2% body weight. This means that if there are sufficient breaks and the players are given access to drink, they will drink enough and this will prevent levels of dehydration that may have an impact on performance. We did not assess whether they drank to thirst only, or whether they used knowledge around drinking to adjust their intake. The training sessions used for these measurements were “typical”, but of course it cannot be excluded that longer sessions may produce slightly different results.
Players adequately adjusted their fluid intake to prevent hypohydration greater than 2% of pre-exercise body mass. No player lost more than 2% body weight.
Low carb intake and no variation
Carbohydrate ingestion was low and was not different between conditions, with a large range in the rate of ingestion between individual players. Several studies have suggested that intakes around 60g/h can result, not only in improvements in running performance but also in skill performance (check this article on this topic). Intakes were considerably lower. For lower intensity sessions, or sessions where quality is not essential, this will not matter, but any session that aims to simulate a match and/or where "quality" is important, a higher carb intake should be considered. It is known (from other studies) that carbohydrate intake during matches is higher, but still below the recommendations.
Carbohydrate ingestion was low and was not different between conditions, with a large range in the rate of ingestion between individual players.
Modest sodium loss with no difference between conditions
Thigh sweat sodium concentration was not different across conditions. There is considerable variability in sweat rate and sweat sodium concentration in professional players. However, this study suggests that individual sweat sodium concentration do not change over time or between different sessions. This suggests that if a practitioner wants to know a player's sweat sodium concentration this does not need to be performed every session.
This study shows that sweat losses are modest in many conditions but it also shows that there are large individual differences. Therefore recommendations of fluid and carbohydrate intake should be specific to the individual player and exercise occasion. Assessing players sweat rates and sodium losses during exercise remains a simple first step in personalising players overall sports nutrition recommendations.
Rollo I, Randell RK, Baker L, Leyes JY, Medina Leal D, Lizarraga A, Mesalles J, Jeukendrup AE, James LJ, Carter JM. Fluid Balance, Sweat Na+ Losses, and Carbohydrate Intake of Elite Male Soccer Players in Response to Low and High Training Intensities in Cool and Hot Environments. Nutrients. 13(2):401, 2021.
This study was a close collaboration with the medical and nutrition staff of FC Barcelona and the Gatorade Sports Science Institute where Dr Ian Rollo works.