The human body constitutes approximately 60% water which is a key component of every cell contained within it. Hydration is key to keeping performance optimal in any environment but especially in hot climates when physiological systems work maximally to maintain bodily function and output. Exercising increases breathing and heart rate as well as the production of the hormone vasopressin from the pituitary gland, aiding water regulation and retention. Vessels close to the skin dilate and blood flow is directed away from none-essential organs towards the skin, raising sweat production to aid thermoregulation. In heat, these mechanisms are working at an optimal pace as the body is placed under increased stress.
Concentration is the ability to focus the mind on a task and is required when participating in any sport, particularly at elite levels during a major tournament. Tactical and technical decisions are made requiring split-second judgements – some consciously and others from the ingrained abilities from many hours of training. Just a 2% loss in hydration can begin to impair these (Jenkendrup & Gleeson, 2010) by lowering focus levels and accelerating the onset of fatigue, thus hindering physiological and psychological performance. As athletes can also experience competitive stress and anxiety, psychological reasoning, attention and state of mind can be seriously debilitated. Organising a system to maintain hydration status pre, during and post exercise can therefore help reduce any negative impact on training and competition.
Research studies have highlighted that exercise in a high-temperature environment for an extended period of time (>1 hr) creating more than a 2% decrease in hydration, negatively affects decision-making, perception, psychomotor control and attention (Cian et al, 2000; Cian et al, 2001; Sharma et al, 1986). Other studies have shown that when the opportunity to drink fluids is removed, the athlete’s mood-status decreases, impacting upon effort, motivation and focus (D’Anci et al. 2009). Although general consensus is that cognitive functioning will be affected by a decrease in hydration status, identifying a certain percentage is difficult due to individual variances in perspiration levels, performance abilities and exercise temperatures (Benton, 2011).
To maintain hydration status during warmer training and competition a few key points can be considered:
- Drink before, during and after a game or match. This ensures that hydration levels are maintained throughout limiting the chance of heat injury (cramps, heatstroke) or exhaustion. Feeling thirsty is an indicator that dehydration is already occurring.
- During any exercise, the replacement of water rather than electrolytes is essential due to sweat composition being “hypotonic to plasma” (Jenkendrup & Gleeson, 2010). This helps restore plasma levels and decreases the loss of muscular strength, endurance and coordination as well as cognition and mood. The composition of fluids during a match should suit the individual preferences although drinking often may be difficult in some sports which have set times of play.
- In heat, due to the increased strain from overworking cardiovascular and thermoregulatory systems, it is better to be well-hydrated than dehydrated, delaying the onset of fatigue and impaired cognition which can derive from weariness.
- For exercise lasting more than 60 minutes in hot temperatures,fluids should include a mix of carbohydrates and sodium. 20-60g/L of carbs (sugars or starch) and 20-60mmol/L of sodium to preserve hydration levels and aid performance and cognition.
- Post exercise, sodium replacement is key for rehydrating an athlete and should be replaced alongside the water lost via perspiration. At least 1.5 times the sweat loss must be replaced in a 6 hour period post-exercise for good recovery. For rapid recovery of severe dehydration 1.5L of fluid should be ingested for every kilogram of weight lost (ACSM, 2002 & 2007). The inclusion of sodium in this will activate a persons thirst and aid fluid retention.
ACSM (2002) Guidelines on Fluid Intake for Exercise
ACSM (2007) Position Stand on Exercise and Fluid Replacement
Benton, D. (2011) Dehydration Influences Mood and Cognition: A plausible hypothesis? Nutrients. V 3, 555-573.
Cian, C.; Koulmann, N.; Barraud, P.A.; Raphel, C.; Jimenez, C.; Melin, B. (2000) Influences of variations in body hydration on cognitive function: Effects of hyperhydration, heat stress, and exercise-induced dehydration. J. Psychophysiol. V 14, 29–36.
Cian, C.; Barraud, P.A.; Melin, B.; Raphel, C. (2001) Effects of fluid ingestion on cognitive function after heat stress or exercise-induced dehydration. Int. J. Psychophysiol. V 42, 243–251.
D’Anci, K.E.; Vibhakar, A.; Kanter, J.H.; Mahoney, C.R.; Taylor, H.A. (2009) Voluntary dehydration and cognitive performance in trained college athletes. Percept. Mot. Skills. V 109, 251–269.
Jenkendrup, A. & Gleeson, M. (2010) Sport Nutrition: An introduction to energy production and performance. 2nd Ed. Human Kinetics: USA
Kleiner, S.M. (1999) Water: An essential but overlooked nutrient. J. Am. Diet. Assoc. V 99, 200–206.
Sharma, V.M.; Sridharan, K.; Pichan, G.; Panwar, M.R. (1986) Influence of heat-stress induced dehydration on mental functions. Ergonomics. V 29, 791–799.
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About Dannielle Starkie
FdSc Sports Science graduate, ex-British champion & international figure skater.