Sports Dietitians Australia accredited sports dietitian Tanya King explains why hydrating during the cooler months is crucial to your performance and well-being.
Winter is here in Oz and some of you may be dreading the dark, early mornings when you start dragging yourself out of bed, layering on the training kit and heading out for a ride in the freezing cold. Wherever you are this winter - Queensland, Victoria, WA - consideration of your fluid and fuel requirements is essential if you’re going to get the most from your training.
Recommendations for fluid intake during exercise
We’re bombarded with advice about fluid and performance, but is this message still relevant in the cooler months? What are the practical implications of a drop in temperature on your usual hydration, fuelling and recovery needs?
There have been significant changes over the last decade in the understanding of personalised sports nutrition and individual fluid requirements during exercise. What is clear is the importance of finding your fluid ‘sweet spot’ because so many factors affect individual fluid requirements and the mechanisms that drive our drinking behaviours are complex.
Factors affecting fluid intake in the cold:
- Individual genetics & physiology – some athletes sweat more than others, even under similar conditions
- Exercise intensity – the higher the intensity, the higher your sweat rate
- Event duration – the length of your ride will affect both your sweat rate but also the opportunities that you have to drink
- Environmental conditions – sweat rates are typically lower in cooler conditions although this can depend on whether you’re facing the outside elements or training indoors sweating up a storm
- Clothing – heavy/waterproof clothing can increase sweat rates in the cold as it limits the loss of sweat from the skin (evaporative and convective cooling)
- Opportunity to drink – there’s typically plenty of opportunity to drink on the bike compared to other sports. However, race tactics or bike handling skills can affect opportunities to drink, especially at higher intensities
- Palatability of drinks – flavoured drinks can help increase the drive to drink when thirst is often blunted. Salt content and drink temperature can also help but chilled water bottles probably won’t be necessary
- Fuelling goals – many riders consume carbohydrate during exercise via sports drinks which simultaneously meet fluid and fuel needs
Other factors that can influence fluid intake include fear of the need to urinate, body weight concerns (excess caloric intake with sports drinks), awareness & familiarity of personal sweat rates, and individual drinking behavior.
Hydration guidelines have evolved over the last 30 years from various schools of thought …
- Drink to thirst
- Drink ad libitum
As much as athletes may crave the security of having a concrete plan e.g. “drink 250ml at every aid station," this one size fits all approach cannot be applied sensibly for all endurance athletes…the factors listed above are testimony to this rule.
So yes, we know very well that dehydration of as little as 2% of body weight can hinder performance by impairing the body’s ability to regulate heat, research has shown however, that dehydration of up to 3% of body weight only has a marginal influence on aerobic exercise performance in cool conditions. While more aerobically fit athletes may be somewhat protected from dehydration, on the flip side, fitter people also tend to sweat earlier during exercise and in larger volumes so this isn’t an excuse to get lazy with your fluid intake.
What about the type of fluid?
Winter is often a time to focus on general conditioning and building a solid endurance base for the summer race season. Athletes may also use this time to achieve body composition goals such as reducing body fat levels, increasing muscle/strength, or simply to maintain weight and stay lean. Because liquid calories are less filling compared with solids, it can be easy to over-shoot your total energy needs by drinking calorie containing drinks, especially if you have a tighter energy budget. Drinks such as cordial, soft drinks, sports drinks, milk shakes/smoothies, fruit juice, and alcohol should be moderated accordingly outside of training with sports drink used only during extended training to optimise carbohydrate availability where necessary. Diet/sugar-free varieties of soft drinks and cordials as well as sugar-free electrolyte tablets (e.g. Nuun, Shotz) may help to boost fluid intake when the drive to drink is dulled in cooler weather. Similarly, drinking 1-2 cups of water with meals can also help to optimise fluid retention by virtue of the salt content of everyday foods without the need to consume extra electrolyte sports products. Hydration is a 24/7 sports nutrition strategy, not just something you need to consider during training.
Do tea, coffee, and caffeinated drinks ‘count’?
Flat white, latte, tea, hot chocolate…it goes without saying we tend to drink a lot more of these hot drinks in winter. Caffeine has long been recognised as a diuretic and is ‘dehydrating’. This myth STILL abounds all over the place…airlines, internet, magazines and even many doctors still advise their patients that tea and coffee are NOT included as part of their total daily fluid count. Based on the current evidence, if you are a habitual caffeine consumer there is no evidence that caffeine is a diuretic when consumed in moderate amounts (<300mg). An espresso coffee has ~120mg of caffeine, 375ml Coca Cola 49mg, 250ml can Red bull 80mg, and Gu Espresso gels 40mg. In my experience working with athletes, the elderly, and general population – there is no requirement to recommend avoiding tea/coffee as this can have significant implications to total fluid intake and the risk of dehydration. Completely counter-productive!
Keeping check of your hydration status
Any or a combination of daily fluctuations in body weight, colour and volume of urine produced and feelings of thirst are useful tools to assess as to whether you are keeping pace with your daily fluid needs. For instance, if you wake-up lighter, produce a small amount of dark coloured urine and feel thirsty, chances are you have failed to keep pace with you fluid losses in the previous 24 hours.
Body weight – daily fluctuations in body weight are usually related to changes in fluid balance. Daily weight loss in excess of 1% may mean you have failed to rehydrate effectively from the day before
Urine colour in the mornings – dark yellow = less hydrated, light/pale yellow = better hydrated
Urine volume during the day – if sweat losses are high, less urine is produced even if you think you may be drinking enough. If you only need to wee once or twice during the day and your urine is dark in the morning, it’s likely your not keeping pace with your daily fluid losses
Like much sports nutrition advice, there is no ‘one size fits all’ approach to hydration and this is especially relevant with seasonal changes in requirements. Personalised hydration strategies have evolved markedly and the more you learn and experiment on yourself, the more strategic you can be with your nutrition strategies to gain that performance edge.