IB SEHS A.2.1 Water and Electrolyte Balance

Refer to the urine color chart. If an athlete’s urine consistently matches color D, what does this suggest about their hydration status?

• The athlete is optimally hydrated; electrolyte excretion is balanced

• The athlete is slightly dehydrated; risk of hyponatremia is increased

• The athlete is dehydrated; reduced plasma volume may impair thermoregulation

• The athlete is overhydrated; antidiuretic hormone (ADH) is being suppressed

What is the main effect of low sodium levels (hyponatremia) during endurance events?

• Faster reaction times

• Muscle cramps and confusion

• Increased energy levels

• Decreased sweat rate

Which is the most common electrolyte lost in sweat during exercise?

• Magnesium

• Sodium

• Potassium

• Chloride

Which mechanism causes water to follow sodium during rehydration?

• Osmosis

• Diffusion

• Filtration

• Active transport

Why is potassium important for recovery after intense training?

• It stimulates glycogen synthesis in the liver

• It helps restore normal electrical function in the muscle and nerve cells

• It increases oxygen binding in haemoglobin

• It reduces adrenaline release

Why is sodium essential in maintaining fluid balance during exercise?

• It prevents protein breakdown in muscles

• It maintains osmotic balance and helps retain water

• It reduces lactic acid production

• It increases glycogen storage

An ultramarathon runner overhydrates by drinking excessive plain water without electrolytes. Which condition is most likely to occur?

• Hypernatremia

• Hyponatremia

• Hypoglycemia

• Hyperthermia

Which electrolyte is most important for muscle contraction during exercise?

• Calcium

• Iron

• Zinc

• Vitamin D

Why do sports drinks often contain carbohydrates as well as electrolytes?

• To slow hydration

• To provide energy for working muscles

• To decrease insulin sensitivity

• To reduce glycogen storage

After cycling in hot conditions, why might an athlete experience muscle cramps?

• Increased glycogen storage

• Excess adrenaline secretion

• Loss of sodium and potassium through sweat

• Low oxygen supply in the lungs