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Hydration and the Effects of Dehydration

Why a performer must stay hydrated: what dehydration is, how losing too much water thickens the blood, raises the heart rate and body temperature, slows reactions and brings on cramp, and how drinking fluid before, during and after exercise prevents it.

⏱️ 15 min 🎯 14 activities
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What you'll cover

Why fluid matters

A performer loses water as sweat during exercise, and if that water is not replaced they become dehydrated. Dehydration is an excessive loss of body water, and it harms performance in several linked ways. The blood thickens and flows more slowly, the heart has to beat faster, the body overheats, reactions and decisions slow down, and the muscles tire and cramp. Staying hydrated by drinking fluid before, during and after exercise keeps all of this at bay. This module covers what dehydration does and how to avoid it.

Hydration words

Learn these four words before you sort any effect of dehydration, and be ready to link each one to a clear drop in performance rather than just naming it. The exam rewards explaining the chain from lost water to poorer play.

Hydrated against dehydrated

The same performer works very differently depending on their fluid levels. This contrast is the heart of the topic.

How to link the effects

Do not just list symptoms. Trace how one loss leads to the next: losing water thickens the blood, so it flows more slowly and the heart must work harder while the body overheats. That in turn slows reactions and decisions and brings on tiredness and cramp, all of which lower performance. Then give the simple prevention: take on fluid before, during and after exercise. Explain the chain, and pair the problem with its fix.

Match the effect to what happens

  • the blood thickens
  • the heart rate rises
  • the body temperature rises
  • the muscles are affected
  • its viscosity increases so it flows more slowly
  • the heart must beat faster and can become irregular
  • the body overheats and struggles to cool down
  • they tire quickly and are more likely to cramp

What is dehydration?

Which statement best describes dehydration?

  • An excessive loss of body water that harms how the body works.
  • Drinking far too much water before a game.
  • Having too much body fat.
  • A lack of protein in the diet.

Effects of dehydration

Select the TWO effects that dehydration has on a performer.

  • A rising heart rate that can become irregular
  • Slower reactions and poorer decisions
  • Muscles that become much stronger
  • A body that cools down more easily

Count the bottles

A player drinks 2 bottles of water before a game and 3 more bottles during it to stay hydrated. Add these to find how many bottles they drink in total. What is the answer?

Order how dehydration harms

Put the chain of dehydration in order, earliest first.

  • Water is lost as sweat and not replaced
  • The blood thickens and flows more slowly
  • The heart works harder and the body overheats
  • Reactions slow and the muscles tire and cramp

Complete the facts

An excessive loss of body water is called _____. It makes the blood thicker, raising its _____, so it flows more slowly. The body also overheats as its _____ rises. A performer avoids this by drinking _____ before, during and after exercise.

dehydration viscosity temperature fluid digestion density strength protein

Match the situation to its result

  • a runner sweats heavily and drinks nothing
  • the blood becomes thick and slow
  • the body cannot lose heat fast enough
  • a player sips fluid through the whole match
  • they become dehydrated and perform worse
  • the heart must beat faster to move it
  • the body temperature keeps rising
  • they stay hydrated and keep performing well

Spot the true hydration facts

Tap the TWO statements that are true about hydration and dehydration.

  • Dehydration thickens the blood and slows its flow
  • Dehydration makes muscle cramp more likely
  • Dehydration helps the body stay cool
  • Dehydration speeds up reactions and decisions

Advise the performer

Read each case and choose the best answer.

  • A hockey player has drunk no water on a hot day and now feels dizzy with a racing heart and heavy legs. What is most likely happening?
  • A coach wants to keep players performing well through a long match in the heat. What is the best advice?
  • A student explains that thick, slow-flowing blood is one effect of dehydration. What is the correct word for this thickness?

Explain dehydration

Explain what dehydration is, how it affects a performer, and how it can be prevented.

  • Explain what dehydration is
  • Explain how it changes the blood and the heart rate
  • Explain how it affects body temperature, reactions and the muscles
  • Explain how a performer can prevent dehydration