Fluid loss test

Tried to work out my rate of fluid loss today (or put less nicely, my 'sweat rate'!)

I weighed myself before exercise and was 164.4lb (74.57kg)

I then exercised for exactly one hour over a hilly multi-terrain course at a reasonable intensity.

I removed running gear and dried myself and weighed in at 162.2lb (73.57kg)

There was therefore a fluid loss of 2.2lb or just about exactly 1kg.

This means that I should be aiming to take on board 35.2 ounces of fluid or just over 1 litre of water for every hour's running.

Current thinking seems to suggest that runners are guided by thirst rather than some pre-conceived idea of their sweat loss, however it is good to have an idea of roughly how much fluid I should be looking to have available/take on during the various legs of the WHWR.

What I have learned:

• During cool weather, carrying a 1.5kg backpack, over a hilly multi-terrain course, excercising at a reasonable intensity, my fluid-loss rate is roughly 1 litre per hour.

The run itself was fun - Chevin run with one cracking hailstorm - ouch!

I will repeat this test during warmer weather to see what difference that makes, and also repeat it running at a much lesser intensity (nearer to race pace for the WHWR).

Sweat rate

I have been reading the medical guidelines sent through by Dario and have come to the conclusion that I have no idea how much I sweat. It is apparently very important to know your sweat rate and it is strongly advised (if not compulsory) to weigh myself during the WHW event in June (to check I am not over-dehydrayed). Race medical guidelines state that runners should be guided primarily by thirst, but I think as always a balance is the optimal approach. I will be guided by thirst to some extent, but a knowlege of my sweat rate will help me to make sure I a) have enough liquid for each stage of the event and b) that I am taking somewhere in the right region of liquid on board.

I came across this article on the web which seems quite useful in determining a person's sweat rate:

Step 1: Weigh yourself before you walk, bike, jog, run, hike, Rollerblade,
play basketball, soccer or work in the garden. For example, let's say you weigh
154 pounds before you start exercising.

Step 2: Exercise for one hour in the weather conditions and at the same
workout intensity you expect to face for an upcoming run, game or special
event.

Step 3: After your workout, remove your perspiration-filled workout clothes.
Dry yourself thoroughly. Weigh yourself again. For example, let's say you weigh
150 pounds after your workout.

Step 4: To calculate your sweat rate per hour of exercise, subtract your
ending exercise weight of 150 pounds from your beginning weight of 154 pounds.
The difference of 4 pounds represents your fluid loss during exercise.Since you
should drink 16 ounces of fluid for every pound of fluid you sweat out during
exercise, multiply the number of pounds lost by 16. In this example, you should
drink 64 ounces of fluid to counteract the symptoms of dehydration and return
your body weight to normal.

Step 5: If you drank any fluid during your 60 minutes of exercise, you'll
need to add that number to the total amount of fluid lost during exercise that
you calculated in Step 4.

Here's another way you can use the information. Once you know your personal
sweat rate per hour, you can incorporate fluid breaks in your training so that
every 15 or 20 minutes you consume 10 to 12 ounces of fluid.

So tomorrow I am going to try this out by running at roughly my race pace over multi-terrain for one hour. The weather is set to be chilly over the weekend so that will obviously affect the results but it is a good cool weather guideline. I will repeat the test when/if we get some warmer weather!