Sweat Rate Calculation

The amount of moisture you produce while exercising is utilized to calculate how much liquid should be consumed before, during, and after engaging in physical activity. This can be measured by looking at your weight change over several exercise bouts to get a feel for your own personal sweat rates under different exercise and environmental conditions, where:

The amount of sweat lost can be calculated by taking the variation in body mass in grams plus any fluid intake in millilitres, and then subtracting the urine loss in grams.

Checking your weight before and after doing physical activity can give you a good indication of how much water your body has lost while exercising. The disparity in mass is reflective of the amount of moisture that has been sweat out, with every kilogram of weight reduction equivalent to 1 litre (1000mL) of sweat.

Once you discover how much liquid you lose every hour of exercise, it’s advisable to replenish about 80% of it, in this case, that would be 800mL.

When you complete your workout, it’s important to replenish the fluids you lost by consuming 150% of the amount you were lacking. To give an example, if you haven’t replaced 400mL of fluids following exercise, then you must drink an additional 600mL of liquid.

The amount of sweating differs significantly among people, with females generally perspiring less than males. For instance, within one sports team performing similar activities, females may sweat at a rate between 600 – 1,200 mL/hr, while males could sweat between 800-1,400 mL/hr.

We should aim to drink regularly from the beginning of our physical workout and stay hydrated throughout the whole session, instead of guzzling down fluids at the end.

If you delay drinking water, your body may not be able to process it as effectively, since the circulation will have moved to other parts of your body, like your muscles.

It is important to make sure to drink an adequate amount of liquids while in training. This can help you gradually become accustomed to higher levels of intake and ensure that your stomach can tolerate a suitable quantity of liquid.

To calculate how much sweat you lose when training or in competition, you will need to:

Take off all your accessories such as a hat, socks, shoes, and shirt, then step onto the scale to check your weight before engaging in physical activity.

Exercise for one hour at your targeted intensity**

Track your fluid intake during exercise (measure in MLS)

Record weight (with minimal clothing) after exercise

One way to find out your hourly perspiration rate is to take the change in your weight from before and after physical activity then add the amount of liquid drank (3rd step).

Keep track of the environmental factors on this day, and make another record at a later time when the temperature has shifted (colder or hotter). This will give you an idea of how various situations can alter your sweat rate.

Warning: This technique is only a rough approximation of the suggested amount of fluid to consume. If you need guidance for more intense training and competition, it would be wise to talk to a sports nutritionist.

Benefits of Being Well Hydrated

Making sure to drink enough fluids before beginning any physical activity will ensure your body is in the best possible condition to reduce dehydration while partaking in strenuous activity. Maintaining the right amount of blood in your body can be assisted by this, as well as allowing you to perspire to dissipate heat satisfactorily.

Athletes that are adequately supplied with fluids tend to have increased focus and a greater capacity for learning skills. Using POWERADE ION4 is a great way to stay hydrated!

Your Body When Dehydrated

The following are some examples of what could happen to your body when you are dehydrated:

When dehydration begins, the amount of blood in the body decreases, which causes it to become thicker and move more slowly. The strain on your heart increases due to the need for it to work harder for it to send oxygen and glucose to the muscles.

Muscular exhaustion: Your energized muscles become weak and worn out.

Mental fatigue: Reaction times, concentration and decision-making ability decrease.

When the body does not contain enough fluid, its ability to sweat and decrease temperature is reduced, leading to an increase in core temperature.

Signs and Symptoms of Dehydration

It’s important to recognize the following signs of dehydration. Some of the symptoms include:

  • Increased thirst
  • Dry mouth
  • Light-headedness
  • Fatigue
  • Impaired mental focus
  • Low / Dark urine output
  • Dull headache
  • Increased heart rate

Your body is telling you that you are dehydrated because you feel thirsty. A mere two per cent loss of fluids due to dehydration (equating to 1.4kg in the body of a 70kg person) may have a conspicuously bad result on performance.

Not having enough water causes body temperature to rise, the heartbeat to become faster, feelings of difficulty with an activity, a decrease in physical capability, and decreased mental alertness.

Therefore, drinking fluids during physical activities can reduce any possible harm, particularly when the exercise is longer and more strenuous. It appears that consuming cold beverages can be advantageous when working out in warmer conditions because it appears to assist in regulating your body temperature.

Physical and mental abilities may be affected by even slight dehydration, while an extreme lack of fluids can be fatal. Someone can become dehydrated fast in certain conditions, including high temperatures.

Be aware of your hydration levels to perform optimally, and make sure to drink enough liquids over the day.

Using Urine Color as an Indicator of Hydration

The shade of your urine is often a reliable way to tell how hydrated you are.

If your urine is light or see-through, then you’re usually fine unless you’ve consumed a large amount of liquid with no sports drink or a salty meal, meaning no water is retained. If the urine is a darker yellow, you are not hydrated or have consumed large amounts of vitamin B and/or C supplements.

Calculating Sweat Rate

This is slightly adapted from Asker Jeukendrup’s excellent mysportscience.

1. Take a bathroom break and then log your body weight, preferably without wearing any clothing. That’s A.

If you’re uncomfortable getting undressed in a place like a gym, you can estimate your weight by weighing your clothes and subtracting their weight from them – this is referred to as ‘The Hovda Method’.

2. Carry out your session (or event) and make a note of exactly how much you consumed.

It is not difficult if you consume the contents of one or two containers.

Measure the weight of your containers before filling them (X) and then again after (Y) and write down the variation. 1 gram = 1 millilitre.* (Z)

If you measure using a range of units, for example, fluid ounces, you will have to convert them all to litres using Google. Make sure all units are in kg or litres

3. After working out, pat yourself down with a towel and then write down your weight. The best option is to go without clothes since wearing them will lead to sweat collecting in the fabric. That’s B.

4. Subtract your weight after exercising (B) from your weight before exercising (A) to figure out how much you lost during the activity.

Weight lost (C) = A-B

5. Also, take away the mass of the bottle(s) before X and after Y to find out the quantity that was drunk, which would be Z.

Volume consumed (Z) = X-Y

6. You can now calculate your sweat rate…

(C+Z) / time.

It’s recommended that you avoid urinating during the activities to get accurate results. If you must go to the restroom, it’s reasonable to assume that you will lose around 300 millilitres of fluid each time.

In the end, reduce your calculated sweat rate by 300ml (0.3kg).

This is because too little of a time difference can lead to errors when figuring out equations, while too long of a time difference can cause baloney results due to the use of fuel and glycogen used while exercising, which can have an effect on body weight results.

You can simplify the calculations by putting all the data together in this spreadsheet together with some notes about the workout (style of exercise, length in minutes, level of difficulty, temperature, and whether it took place indoors or outdoors).

What to do (and not do) with the data

Once you have gathered an adequate quantity of perspiration rate information, the natural inquiry is what can be done with these figures? Unfortunately, the resolution to the issue is not as uncomplicated as many athletes would wish.

Frequently, athletes will partake in sweat rate tests and then determine that if they run hard, for instance, and perspire a litre per hour, then they must drink one litre per hour when running to replace all of the lost fluids.

The principle of ‘one in, one out’ is simplistic and has commonly been believed to create an optimal result when 100% of the sweat is replaced during exercise.

However, research has demonstrated that this thought process is deeply mistaken (because the complexities of sustaining performance during an active period are immense). Few, if any, reliable fitness experts or dieticians would suggest now that electrolyte and sweat losses during activity should be exactly compensated for.

It is hazardous to drink more than what one feels an inclination to drink, as this is often necessary to achieve full hydration.

There is a possibility of getting hyponatremia ( with its severe consequences) if someone drinks too much water, and this alone should be enough to convince people to not aim at consuming 100% of their fluid needs.

What percentage of your sweat losses should you aim to replace

One’s ability to handle dehydration (measured by body weight loss) is fairly high if they start off already properly hydrated before beginning to train or compete.

It is uncertain how much you must replace at any given moment; it is likely very personal and is likely to be different from day to day.

This blog provides useful information on your endurance in regards to dehydration and it offers insights on how much water loss your body can withstand before it affects your physical performance. It’s a valuable read that will help you understand how much fluid you need to replace.

It is pointless to rely on sweat rate measurements to construct a rigid, unchanging approach to replacing fluids and electrolytes.

Getting an estimate of how much sweat (and sodium if you are aware of your sweat composition) you will lose over a particular period, at an intensity level and in specific environmental conditions should be your goal when measuring your sweat rate.

Doing multiple tests to gauge fluid and sodium levels during practice or competition can be extremely useful in determining the intakes you need to optimize your performance. Experimentation will be necessary to find the optimal amounts.

It is important to remember that the sweat rate calculation should be used as a REFERENCE POINT, and always trust your body’s cues when considering adjustments.

It is unreasonable to count on always abiding by a plan, as running a race is constantly changing (with alterations in pace, environmental temperatures, and body conditions influencing metabolism and perspiration/liquid loss at the moment).

Avoiding Hyponatraemia

Hyponatraemia, or low sodium levels in the blood. This happens when a person drinks more liquid than the kidneys can clear out, particularly during physical activity, when the kidneys tend to work less effectively.

Symptoms of hyponatraemia may be akin to those of dehydration – such as headaches caused by brain swelling, confusion, nausea, and vomiting.

The majority of instances of hyponatraemia have been found in prolonged marathon events that last over 6-8 hours, and those who are prone to be affected are normally those who have a slower running pace and can consume a lot of fluids.

It is not certain that having a sports drink will lower the possibility of danger, nevertheless, it could be beneficial if the amount drunk and the rate of perspiration is kept in proportion.

The principal concern is to avoid drinking an excessive amount of alcohol at the event so that you don’t put on any extra weight. Try to finish the event at the same, or slightly less, body weight than when you first arrived.

It is helpful to be aware of how much you sweat in different types of weather to make sure that you are drinking the right amount of fluids, not too much and not too little. Look at “How to Estimate Your Own Sweat Rate” for assistance.

Measuring sweat rate in practice

Let’s say you’re losing ~0.5l of sweat per hour. It is improbable that you will gain much more than what you need by just drinking according to thirst, as the amount of fluids and salts you will lose over time is not likely to be very big.

If more than 1.5L of fluid is being lost each hour during an extended workout, aggressive hydration is necessary to prevent becoming dehydrated and deficient in sodium.

Acting ahead of time during the initial period of extensive meetings and extended occasions will be useful in decreasing a large number of losses probable in the end. If you tend to sweat a lot and your sweat also contains a great deal of sodium, then this is especially true.

By finding out how much sweat you produce (and its concentration) and using this to modify your intake, you will be more likely to come up with a good hydration method that will be effective when you need it the most.


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