Why does a day laying in the sun make you tired?

In addition to given answers.

Sun light brings some chemical changes in the body. Few substances, mostly Vitamin K and some pigments, are produced by action of sunlight.

Normally, body is adjusted to production of these substances for shorter periods but duration of whole day makes the body to produce more than the normal practice.

The abnormal production results in disbalance of substances in the body.

On the whole muscles are damadged more than their repair and the acids which give sense of tiredness (by inflamation)ar neither oxidized nor utilized.

Thus the body becomes more tired.

Sun Makes Me Tired

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RE:

Why does a day laying in the sun make you tired?

It seems like even if you spend a day sleeping on the beach you leave much more tired than when you arrived at the beach. I am interested in the scientific reason for this. Websites for reference would also be appreciated!

There are two primary reasons. 1, you become dehydrated from evaporative cooling (sweat), which is very fatiguing-and generally have an imbalance of salts as well. 2. you have an inflammatory reaction in the skin, due to the sun and heat. The skin is a huge organ, the largest of the body, and having it swell and inflame is extremely stressful physiologically. This also contributes to dehydration, as your skin draws off much of the body's water during the inflammation process.

Depletes alot of essential vitamins as well causes Melanoma one of the most deadly cancers in the world. Just a true heads up.

Because your body is using energy trying to cool you down and maintain it's normal temperature.

robinkennedy1 is correct..