1800 352 330
Register   |  Log in  |  Help

Home » Blog » Staying hydrated during Trailwalker using ELOAD

Staying hydrated during Trailwalker using ELOAD

“Not getting dehydrated should be a primary goal of every participant. This article helps you understand how to better manage hydration. Have a hydration plan, don’t just plan to drink when you feel thirsty.”

Minimizing dehydration is the simplest, yet the most effective step Trailwalker’s can take to manage both their health and performance during the event. Most people (including many athletes) allow themselves to become slightly or moderately dehydrated during exercise, training and competitions. Dehydration impairs both physical and mental performance in all types and levels of sport, yet it can be avoided, or at least minimized by an appropriate hydration strategy.
Dehydration means your body does not have as much water and fluids as it should. Dehydration can be caused by losing too much fluid, not drinking enough water or fluids, or both. And prolonged exercise without an adequate rehydration strategy will inevitably lead to it in some degree or other.

Importance of water

Our bodies contain about 60% water by weight, with almost half of this residing in muscle cells. Water is essential to all metabolic processes, including maintaining blood volume, regulating body temperature and allowing muscle contraction to occur. Under normal conditions this water content and thus our metabolic processes are relatively constant.

Effects of Dehydration on Physical Performance

During vigorous or prolonged exercise large quantities of water and electrolytes are lost through sweat as the body tries to maintain an optimal temperature. This rate of loss is dependent on a number of factors including:
• Temperature
• Humidity
• Exercise intensity
• Exercise duration
• Clothing
• An individual’s metabolism

In fact sweat rates of between 0.3 to 2 litres per hour are common in people during sport and exercise depending on conditions.

A change in body weight due to water loss of 1% is a marker of early dehydration. At 2% water loss, most people will begin to experience a decline in physical and mental performance and as you can see from this example it does not take long to get dehydrated.

If a 70kg person undergoing intensive training/exercise, has a sweat rate of 1.5lt per hour, they will hit the 2% dehydration level within the first hour of exercise if not taking any measures to offset dehydration.

The graph outlines the potential impact on a person’s performance as their rate of dehydration increases:

Adapted from Wilmore & Costill (1999) ‘Physiology of Sport & Exercise’. Human Kinetics.

The effects of dehydration can include
• Reduction in exercise performance (speed and power output)
• Reduction in the time to exhaustion
• Increase in the perception of exercise difficulty (much less enjoyment)
• Reduction in mental performance (alertness, concentration, visual motor skills and decision-making)
• Dehydration and sodium loss can lead to muscle cramps
• Increase in the risk of blisters and chaffing
• Increased amount of lactic acid in muscles
• Dehydration is a risk factor for heat exhaustion and heat stroke, both serious conditions

Dehydration impairs both physical and mental performance. Fluid loss as low as 1-2% of total body weight affects temperature regulation and reduces endurance capacity and aerobic performance. Higher levels of dehydration impair mental concentration, alertness, muscular strength and endurance, physical work capacity, and increase risks for heat injury.

How to measure your rate of dehydration

Knowing your sweat rate can give you an indication of how much you should be drinking during exercise. To do this you can easily take measurements during training over a range of environmental conditions to establish some average rates.

The following procedure can be used to establish your sweat rate

Step 1:
Immediately prior to the start of the training or exercise session measure the pre-exercise body weight (A in kg) on accurate scales. Ideally you should remove most of your clothing

Step 2:
Immediately after the exercise, towel off the excess sweat, and measure your post-exercise body weight (B), wearing the same as you wore in measurement (A). Calculate the total body weight change (C = A – B in kg)

Step 3:
Record the drink volume consumed during your training session, measurement (D) expressed in kg (Assume 1L = 1 kg and 1 ml = 1g)

Step 4:
Record the urine volume passed during exercise, measurement (E) expressed in kg (Assume 1L = 1 kg and 1 ml = 1g)

Step 5:
Calculate the sweat loss (F) based on F = C + D – E (in kg) and then convert to litres (Assume 1L = 1 kg and 1 ml = 1g)

Step 6:
To Calculate the average sweat rate(G) take measurement ( F in litres) and divide by the exercise duration in hours


You train for 2 hours, with pre- and post- body weight measurements of 70 and 68 kg. During the session you drink 1000 ml water and pass 500 ml of urine.

C = A – B = (70 – 68 kg) = 2 kg
F = C + D – E = (2 + 1 – 0.5 kg) = 2.5 kg = 2.5 Litres
Your average sweat rate G = 2.5 litres in 2 hours or 1.25 litres per hour
NB: In this example the person is in a dehydrated state at the end of their session.

Your weight change during exercise generally reflects your fluid loss, (unfortunately not your fat loss) and can be calculated at 900ml for every 1kg of weight difference.

Once you have some numbers you can start to calculate some pretty accurate sweat rates. It is from these that you can develop the most effective hydration strategy.

During exercise, it is normal (depending on the individual and the conditions) to have a sweat rate of between 0.3-2.5 litres per hour. Although sweat rates are highest under conditions of high-intensity exercise in heat and high humidity, total fluid losses can be appreciable in very prolonged events like Trailwalker, whatever the conditions.

Fluid Replacement during Training and Trailwalker

Ideally the goal of your hydration strategy should be to replace fluid and electrolytes lost through sweat at the same rate as the loss, or at worst try to prevent the body from losing more than 2% body weight from such losses.

It is possible that an individual’s rate of fluid loss may exceed the capacity of their gastrointestinal tract to reabsorb fluids. There is large individual variation in gastric emptying rates and tolerance to large volumes of fluid, so training to drink during your pre-event training is recommended and may enhance tolerance.

Water or Sports Drink?

Water alone can be an effective drink for fluid replacement, especially in low intensity and short duration sports. Over-hydrating or trying to meet your fluid needs during very long-lasting events, such as the Trailwalker, with low or negligible sodium intake can result in reduced performance and if very unlucky hyponatraemia¹

Maintaining proper electrolyte levels in endurance events is critical to performance.
The key to rapid and complete rehydration is to provide enough electrolytes in your rehydration beverage to serve as an osmotic impetus to restore and maintain extra-cellular fluid volume, including blood volume. And this depends upon ingesting both the fluid as well as the electrolytes that are lost in sweat.

Sodium, Potassium, Calcium, Magnesium, Zinc and Chloride are an important part of a sports drink for performance, as all are lost through sweating. These electrolytes are responsible for maintaining many functions in the human body, including normal muscle contraction, blood pressure, nerve conduction, heart rate and gastrointestinal motility, to name a few. They also play an important role in energy metabolism.

However many sports drinks have minimal and/or incomplete concentrations of electrolytes, and do very little to counter the electrolyte depleting effects of sweating. It is just as important to select the right sports drink as it is to have a sound hydration strategy. e load Endurance Sports Drink is one such product that has a scientifically proven balance of electrolytes that replaces them in the same ratio that they are lost through sweat.

Further to this the e load range allows you to easily customise your hydration to reflect varying conditions and individual needs.

Sample Hydration Table for Trailwalker

60kg Female Trailwalker
Calculated average sweat rate – 0.75lt/hour
Estimated time for the event – 24hrs
85kg Male Trailwalker
Calculated average sweat rate – 0.75lt/hour
Estimated time for the event – 40hrs
Ideal rehydration rate of 0.75lt per hour
Total fluid required for optimum hydration
24 x 0.75lt or 18 litres

If using a sports drink during the event
ELOAD Endurance required – @1 – 1.2kg

Ideal rehydration rate of 0.75lt per hour
Total fluid required for optimum hydration
40 x 0.75lt or 30 litres

If using a sports drink during the event
ELOAD Endurance required – @1.4 – 1.7kg

NB: Your sweat rate will vary during the event along with the conditions; hills and flats; sunlight and darkness. It is useful to try and understand and account for these differences during training and the event itself.

In Summary

Always start exercise well hydrated; this will lower the risk of becoming dehydrated during exercise. There is minimal performance benefit to being over-hydrated as drinking excessive amounts of fluid before exercise causes increased urination and feeling bloated.

Develop a plan for drinking during exercise based on your own sweat rates.

Electrolytes are those salts which play a major role in the biochemistry and physiological processes of the human body.

Follow an individualised hydration program, which includes the consumption of a properly formulated sports drink, such as e load, as this is one of the most effective ways to prevent dehydration to help keep you safe and performing at your best.

Drink small amounts frequently to optimise fluid and electrolyte reabsorption and keep tabs of your total intake to ensure that you are drinking the right quantity. Remember feeling thirsty is a poor indicator of your hydration levels.

Actively manage your hydration for the duration of the event, as you get tired it is important that you keep to your event hydration strategy.

When you finish a long training session or the event, you will usually have a deficit of water, calories and sodium. You will have a much smoother recovery if you replace all of those promptly. Soon after finishing you can take a sports recovery drink like e load’s Emend and continue to drink fluids until you are no longer thirsty, and are urinating again. In the days that follow, you will find that you have more energy and fewer aches and pains.

By Toby Cogley

¹Hyponatraemia – This is a rare condition that affects ultra endurance participants and is also referred to as ‘water intoxication’. If you consume water-only or an energy drink without electrolytes over a long period of time, the combination of sodium chloride loss through sweating and the dilution of the remaining salts in the blood stream with the fluid you’re taking in can cause headaches, cramping, loss of strength and nausea. If left unchecked, this could become quite a serious condition.

This entry was posted in Blog, Brisbane Oxfam Trailwalker, ELOAD, Home, Nutrition, Run. Bookmark the permalink.

Leave a Reply