Race day Fueling and hydration

Hello all and welcome to this weeks. This comes off the back of a frequent questioned asked on my week Q&A which is how do I fuel and hydrate on race day.

In today’s blog I will address

· The role of water, electrolytes lost through sweating and their importance, Signs of dehydration and hyponatremia,

· How to calculate sweat loss and tactics to employ to stay hydrated before during and after exercise

· Fueling your race, the recommendations

Proper hydration is one of the most important aspects of physical activity

Athletes should employ hydration plans that take into consideration many factors, including sweat rate, climate and level and intensity of training.

By Replenishing fluids and electrolytes, it can aid performance and prevent dehydration and hyponatremia.

Let’s start at looking at the role of water In the body:

Its makes up 60% of our body weight is one of the most vital and most neglected nutrients in our diet.

  • It plays many vital roles that directly affect the athlete’s health and performance.

  • Water is also the main component of blood, which is responsible for transporting nutrients (such as glucose), gases (such as oxygen) and waste.

  • Helps cool the body and maintaining its core temperature.

  • Water removes lactic acid from exercising muscles, and muscle glycogen holds water, which can be an advantage to well-hydrated athletes.

  • Water is also responsible for lubricating joints, moistening tissue and protecting body organs.

Ultimately the athlete’s goal is to take in adequate amounts of fluid and electrolytes to compensate for the fluid and electrolyte losses during exercise

We lose water when we Sweat, sweat is around 99% water ; the other 1% is electrolytes. Electrolytes keep our cells, tissues, and fluids active and able to communicate within our bodies.

Key Electrolytes lost in through sweat include

  • Potassium / Controls fluid and electrolyte balance, assists in the conduction of nerve transmission and helps move glucose into the cell

  • Magnesium- Regulates muscle relaxation and helps other electrolytes travel through cell membranes

  • Calcium - Aids skeletal muscular contraction, nerve impulse transmission and the breakdown of muscle and liver glycogen

  • Soduim- maintain the balance of water in and around your cells. It's important for proper muscle and nerve function. It also helps maintain stable blood pressure levels. If there is a lack of it you may suffer from hyponatremia

  • Athletes can lose 115–2,300 milligrams of sodium per liter of sweat, To put this in perspective, one teaspoon of table salt has approximately 2,000 milligrams (mg) of sodium.

Factors that affect sweat loss

  • Sport

  • Skin and clothing

  • Environment

  • Heat and altitude

  • Level of fitness and diet

  • Body weight and gender- Women have more heat-activated sweat glands than men, but sweat less profusely.


A certain level of dehydration is inevitable with long distance training and racing.

Athletes who lose 2% or more of their body weight during exercise are at risk for suboptimal performance. Inadequate fluid intake may result in fatigue, GI distress, reduced blood flow, increased heart rate and sometimes death.

Signs of dehydration include

  • Thirst,

  • Flushed skin,

  • Premature fatigue,

  • Increased body temperature,

  • Faster breathing and pulse rate, Due to lower blood volume, the heart compensates by beating faster to circulate more blood

  • An increased perception of effort and a decreased exercise capacity.


Hyponatremia is a medical condition in which the concentration of sodium in the blood is lower than normal.

The signs and symptoms of hyponatremia as well as know how to prevent it from occurring

  • Nausea and vomiting

  • Headache

  • Confusion

  • Loss of energy and fatigue

  • Restlessness and irritability

  • Muscle weakness, spasms or cramps

  • Seizures

The combination of dehydration and hyponatremia is called hyponatremic dehydration.

How to calculate sweat loss

Athletes weigh them selves prior to exercise. The athlete should exercise for at least one hour, while keeping track of the quantity of water he or she consumes.

After exercise, the athlete should re weigh themselves making sure to wear exactly what was worn before.

The athlete’s weight before and after exercise, as well as the amount of fluid that was consumed during the exercise, will be used to determine the athlete’s sweat rate.

Subtract the post-exercise weight from the pre-exercise weight in pounds or kilograms and convert to ounces , and add to the amount of fluid that was consumed during the exercise. This will determine how much sweat was lost during exercise.

Tactics to employ before during and after

Fluid Replacement Before Exercise Athletes should consume fluids several hours before exercise.

At least four hours before exercise, athletes should approximately 300ml per each 10 pounds of body weight, consume beverages with sodium (460–1150mg/liter) and/or sports nutrition products and sodium-containing foods to help to stimulate thirst and retain the consumed fluids.

It is important to consume the fluids slowly, rather than all at once. Consuming beverages with sodium will help stimulate thirst as well as retain fluids.

Fluid Replacement During Exercise

During exercise, the goal of drinking fluids is to avoid dehydration. This is accomplished by replacing fluids based on the athlete’s sweat rate and according to his or her level of thirst. Consuming fluids in excess of sweat rate should be discouraged.

To increase gastric emptying, athletes should consume an average of 100ml/300ml of fluid every 15–20 minutes of exercise and consume 500–700 mg sodium per liter

The amount of fluid intake, as well as the rate of intake, will depend on the individual’s tolerance, the type of activity and the intensity of the activity

Fluid Replacement After Exercise

After exercise, the athlete should drink adequate fluids to replace sweat loss.

Coaches should encourage athletes to consume approximately 450 to 675 milliliter fluid for 0.5 kg of body weight lost during exercise. consuming foods and fluids that contain sodium to facilitate rehydration will improve hydration.

Part 2 Fueling for the race

Before I start this, unlike water, the fueling and sodium/ sugar intakes can be quite individual. With this in mind I will offer the larger recommendations when it comes to fueling pre, during and after.

The first thing to assess is the duration of the event, the fueling for a sprint triathlon would be quite different to that of a full ironman, based on length and dominant energy system. As a general rule of thumb an individual has sufficient glycogen stores in muscles and liver to provide 1500-2000cal worth of energy which is around 90 minutes’ worth of activity and is the key point at which time athletes would be recommended to take on some fuel in the form of simple sugar (carbohydrate) for a easy and quick energy kick.

Here are my recommendations pre race on the day.

Pre Race

  • Breakfast on race day should be similar to training days. Best to opt carbohydrates, a little protein, and minimal fats as these can be harder to digest. A perfect example might be Toast and jam, a banana, oatmeal, PowerBar, and Carbohydrate electrolyte drinks. For me personally depending on the time of the race I may or may not take a breakfast. If the race is very early I will eat something on the bike, but I will ensure that the night before I have eaten sufficiently to ensure I have energy for the swim part. I always have coffee on training days, so I will have a coffee on race day.

  • Be Sure to finish breakfast 2-3hrs before race start to give yourself time to digest.

  • In the 2hrs before the race, sip water and/or a Carbohydrate electrolyte drink.

  • Some athletes will take a PowerGel prior to race start, I personally do not.


  • Starting the bike - For the first 5-10 minutes of the bike, drink water and take in minimal calories, mainly in the form of a sports drink. Let your body adjust to cycling, and let your heart rate drop down. Then start eating when you have settled into a good cycling rhythm. Follow the plan you've trained with all season, do nothing new on race day.

  • From 10 minutes after the bike start to 10 minutes prior to the bike finish eat 60-120grams of carbohydrate calories per hour. Some athletes can digest more than others. My main tip is to test it in training.

  • Drink 1 to 1.5 litres (33-50oz) of fluid per hour (water and Carbohydrate electrolyte drink combined). More if the climate is hot and humid. Also base on you perspiration ratio and rate if known Every 1 pound lost is 1 small water bottle of fluid deficit, and will negatively impact performabce.

  • Stick to your fueling plan.

  • In the run up to the run I would recommend reducing your calorie intake and only take in sports drink or water. This allows your stomach to empty while still allowing your gut to absorb the food and fluid ingested earlier on the bike. You will be able to start the run in a relatively comfortable state.


  • Wait 5-10 minutes into the run until your heart rate levels off before starting your nutrition/hydration regime.

  • I find that heart rates are higher on the run than the bike. Meaning eating and calorie intake can be 15-30% lower per hour than on the bike to accommodate for the increase in HR.

  • I personally find liquids / gels easier to digest on the run,

  • Hydration protocol should be similar to the bike.

  • Use the feeding stations a s guide to take on fuel and water.

Thank you for taking the time to read this, I hope that took something away from it that will help in your race day prep.

Until next week

Stay healthy


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