Hydration is a commonly overlooked area of sports performance. Just 2% dehydration (when 2% of your body weight is lost) (1, 2) can have a large impact on performance, including reducing high intensity sprinting by 10% (3), reduced aerobic performance by 10% (4), slower decision making (5), decreased accuracy of fine motor skills and worsened temperature regulation; all of which can impact endurance sports and team sports. Dehydration has been found to reduce strength by 5% and power by 3% (3), posing a potential problem for CrossFit and Hyrox athletes. Dehydration can also impact your rate of perceived exertion (how hard you perceive the exercise to be) (6) and adequate hydration is essential for recovery and muscle repair (7). Many athletes start sports in a dehydrated state (1, 2, 3), and this is exacerbated during exercise, especially in hot and humid environments. Every person’s hydration needs are different, therefore it’s important to listen to your own body and adapt your drinking accordingly.
How much and when to drink
It’s common to lose between 1 to 2L of water during exercise through sweating and water exhaled in the breath (2). In some ‘heavy sweating’ individuals, ultra-endurance events or in extremely hot environments, fluid losses can be as high as 3 to 4L (2, 3). You should always aim to start exercise in a hydrated state, and drink enough fluids during exercise to limit fluid loss to less than 2% (e.g. a reduction in body weight of less than 1kg for a 50kg person, 1.5kg for a 75kg person and 2kg for a 100kg person) (2) - I like to aim for 200-250ml every 15 mins of exercise (8). Weigh yourself before and after exercise to find out how much water weight you have lost. Rehydrating after exercise is also important, and the general rule of thumb is to rehydrate with 1.5x the amount of fluid lost during exercise (e.g. if you lost 1kg of body weight during your training session, you should aim to drink 1.5L of water in the 1-2 hours post-exercise)(1, 2).
How do I know if I am hydrated?
There are multiple methods of measuring hydration, however no one method on its own is 100% reliable, so practitioners often combine a couple of methods to get a more accurate picture of an athlete’s hydration status. The first and easiest method is looking at the colour of your urine (1). Hydrated urine is very light yellow in colour, and the darker the urine is, the more dehydrated you are. The second method is weighing yourself before and after training (as discussed above) to assess how dehydrated you might be post-exercise. Other measures include measuring urine specific gravity and bioimpedance testing, however these are more useful in lab-based or professional sport settings (1, 2). When working out if you are hydrated, ask the following three questions: is your urine dark in colour? Have you lost weight after exercise? Are you thirsty? If the answer to 2 or all of them is yes, then you are likely dehydrated.
Electrolytes: sodium, magnesium and potassium
Sometimes water alone isn’t enough to aid your performance. This is especially the case in (you guessed it!) hot and humid environments, heavy and salty sweaters and in exercise lasting longer than 1-2 hours. Electrolytes such as sodium (salt), magnesium and potassium help regulate hydration via a number of processes. Salt is the most commonly known electrolyte, and it works by aiding water retention and stimulating thirst (9), helping athletes stay hydrated. It is also essential for preventing hyponatremia (low blood sodium levels caused by prolonged sweating). Magnesium is responsible for moving water into cells, which is essential for muscle function energy production. Finally, potassium works alongside sodium to maintain fluid balance in the cells and regulate nerve and muscle contractions. It can offset the presence of too much sodium to maintain electrolyte balance. Symptoms of electrolyte imbalance can include muscle cramps, dizziness, fatigue and confusion, all of which can negatively impact daily life and athletic performance.
Why iidro?
Both iidro drinks contain just under 3g of salt, 300mg of potassium (15% RDA) and 56mg of magnesium (15% of RDA) per 300ml of drink to aid hydration before and rehydration after training.
References:
(1) https://www.gssiweb.org/en/sports-science-exchange/Article/sse-128-hydration-science-and-strategies-in-football#articleTopic_6
(2) https://journal.aspetar.com/en/archive/volume-2-targeted-topic-sports-medicine-in-football/hydration-strategies-for-football
(3) Baker LB, Barnes KA, Anderson ML, Passe DH, Stofan JR. Normative data for regional sweat sodium concentration and whole-body sweating rate in athletes. J Sports Sci. 2016;34:358–363. doi: 10.1080/02640414.2015.1055291.
(4) Cheuvront SN, Carter R 3rd, Sawka MN. Fluid balance and endurance exercise performance. Curr Sports Med Rep. 2003 Aug;2(4):202-8. doi: 10.1249/00149619-200308000-00006. PMID: 12834575.
(5) Gopinathan PM, Pichan G, Sharma VM. Role of dehydration in heat stress-induced variations in mental performance. Arch Environ Health. 1988 Jan-Feb;43(1):15-7. doi: 10.1080/00039896.1988.9934367. PMID: 3355239.
(6) American College of Sports Medicine; Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ, Stachenfeld NS. American College of Sports Medicine position stand. Exercise and fluid replacement. Med Sci Sports Exerc. 2007 Feb;39(2):377-90. doi: 10.1249/mss.0b013e31802ca597. PMID: 17277604.
(7) Cheuvront SN, Kenefick RW. Dehydration: physiology, assessment, and performance effects. Compr Physiol. 2014 Jan;4(1):257-85. doi: 10.1002/cphy.c130017. PMID: 24692140.
(8) Judge, Lawrence W et al. “Hydration to Maximize Performance and Recovery: Knowledge, Attitudes, and Behaviors Among Collegiate Track and Field Throwers.” Journal of human kinetics vol. 79 111-122. 28 Jul. 2021, doi:10.2478/hukin-2021-0065
(9) Veniamakis, Eleftherios et al. “Effects of Sodium Intake on Health and Performance in Endurance and Ultra-Endurance Sports.” International journal of environmental research and public health vol. 19,6 3651. 19 Mar. 2022, doi:10.3390/ijerph19063651