In summer, hydration is highlighted as key for optimal training, but why does this emphasis disappear during winter training? It is just as important, but we are not continually reminded about it through our normal psychological and physiological triggers telling us to drink. In general, we don’t feel as thirsty in colder temperatures and we often perceive our sweat rates to be lower. Dehydration will impair our exercise performance due to reductions in blood volume, blood flow, sweat rate and heat dissipation, which will result in increased core body temperature and also increase the rate of muscle glycogen utilisation, thereby leading to fatigue(1). Water will exit the body in multiple ways, though exhalation, perspiration and urination, and we need to replace fluid lost. Hydration status is very individual and will vary due to environment, individual training demands and sweat rate. What will be enough for one person may not for another so although general guidelines do exist(2), we recommend learning what works for you. Signs you might be dehydrated include headaches, fatigue, cramp, dark urine and overall you may find you can’t perform as well during your session. In winter, there are a few important considerations to take into account; • In cold temperatures, your thirst response is not as active as in warm temperatures(3). Therefore, whilst your body may be working just as hard if not harder, you won’t feel as thirsty. With a repressed thirst response, you could set a timer or reminder on your watch to remind you to drink. • In winter, we often use extra layers to keep warm. We still perspire and due to extra weight (although in most cases minimal), your body may have to work harder. Try to ensure extra layers are made to cope with sweat so your body can still cool down effectively. Then ensure you are re-hydrating efficiently post-exercise. • If you are training indoors over winter (avoiding the cold conditions!), you are likely to sweat! Make sure you start these sessions hydrated, take on fluid throughout and don’t neglect hydration for recovery afterward. If you are doing a turbo session I’d recommend the Turbo+ Powder in citrus. As well as being a carbohydrate-based powder, it contains sodium which is key for hydration. • Recovery from any training session will be improved if you can optimise fluid balance(4). Ensure you consume some sodium to replace what was lost in sweat. This will also increase how much water is absorbed in the body. You can do this using an SiS Hydro Tablets or add some salt to your meal after exercise. • During winter, in general there is an increase in illness due to viruses living longer in colder temperatures and lower humidity. Exercise can reduce your immune system for up to 72 hours post-exercise, though staying hydrated can boost your immune response. SiS Immune Tablets contain a combination of vitamin C, iron and key electrolytes (discussed below), in order to support hydration and immune function post-exercise. As well as water, there are other key ingredients to look for in a drink that will help optimise hydration status. Electrolytes, or minerals that have an electrical charge are key for your body’s normal operation regardless of exercise. Key electrolytes to look for are sodium and potassium(5) which you will find in the SiS Hydro Tablets and GO Electrolyte, personally the lemon and lime is my favourite flavour! The powders also contain a carbohydrate mix of maltodextrin and fructose so are perfect for balancing energy and hydration needs. In summary, don’t forget about hydration over winter. Ensure you are adequately hydrated before, during and after exercise, drink at regular intervals and listen to your body. References 1. Jeukendrup A, & Gleeson M. (2015) “Dehydration and Its Effects on Performance.” Humankinetics. 2. Sawka MN, Burke LM, et al. (2007) “American College of Sports Medicine position stand. Exercise and fluid replacement”, Med Sci Sports Exerc, 39(2),377-390. 3. Kenefick RW, Hazzard MP, Mahood NV, Castellani JW (2004) “Thirst sensations and AVP responses at rest and during exercise-cold exposure”, Medicine and science in sports and exercise, 36, 1528-1534. 4. Evans GH, James LJ, Shirreffs SM, Maughan RJ (2017) “Optimizing the restoration and maintenance of fluid balance after exercise-induced dehydration”, Journal of Applied Physiology, 122(4), 945-951. 5. Maughan RJ (1998) “The sports drink as a functional food: formulations for successful performance”, Proc Nutr Soc, 57(1), 15-23. Written By Dr Emily Jevons - PhD in Exercise Physiology & Nutrition, Clean Sport Advisor Emily has worked with Science in Sport since 2021. With a PhD in Exercise Physiology & Nutrition, she currently provides nutritional advice for endurance athletes. Emily not only understands the science behind performance nutrition solutions, but also the physiological and psychological demands of sport after competing competitively in swimming and triathlon for a number of years.