Short-Term Effects of Exercise

While immediate effects occur during exercise and disappear shortly after, short-term effects are the responses that persist for up to approximately 36 hours after exercise. These effects are part of the body's recovery process and are covered in AQA GCSE PE spec 3.1.1.4. Understanding these effects helps explain why athletes feel the way they do in the hours and days following training or competition.

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What Are Short-Term Effects?

Short-term effects are physiological responses that begin during exercise but continue for a period of time after exercise has finished. They typically last from a few hours up to about 36 hours. These effects are part of the body's natural recovery and adaptation process.

Time Frame	Category	Examples
During exercise	Immediate effects	Increased heart rate, sweating, red skin
Up to ~36 hours after exercise	Short-term effects	Fatigue, DOMS, light-headedness, nausea
Weeks/months/years of training	Long-term effects	Hypertrophy, bradycardia, improved fitness

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Key Short-Term Effects

1. Fatigue

Fatigue is a feeling of tiredness and reduced ability to perform physical or mental tasks. After exercise, fatigue can persist for several hours or even into the next day.

Causes of post-exercise fatigue:

Cause	Explanation
Glycogen depletion	The muscles and liver have used up much of their stored glycogen (the body's primary fuel during exercise). Until glycogen is replenished through food, energy levels remain low.
Lactic acid accumulation	After intense anaerobic exercise, residual lactic acid may still be present or its effects still felt in the muscles.
Dehydration	Fluid lost through sweat during exercise reduces blood volume and impairs bodily functions, contributing to tiredness.
Nervous system fatigue	Prolonged exercise can fatigue the nervous system, reducing the efficiency of nerve impulses to muscles.
Microtrauma to muscle fibres	Exercise, particularly resistance training, causes tiny tears in muscle fibres. The body must repair these, which takes energy and time.

Fatigue in sport:

A rugby player after a match may feel physically and mentally exhausted for the rest of the day and into the following morning. This is normal — the body is recovering from the extreme physical demands placed upon it.

Exam Tip: If asked to "explain why an athlete feels tired after exercise," do not just say "because they exercised a lot." Be specific — mention glycogen depletion, lactic acid, dehydration, and/or muscle damage.

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2. Light-Headedness and Dizziness

Some athletes experience light-headedness or dizziness during or shortly after exercise. This can be caused by:

Cause	Explanation
Blood pooling	If exercise stops suddenly (no cool down), blood can pool in the lower extremities due to gravity. Less blood returns to the heart, so less blood is pumped to the brain.
Dehydration	Loss of fluid through sweat reduces blood volume, lowering blood pressure and reducing blood flow to the brain.
Low blood sugar (hypoglycaemia)	Prolonged exercise uses up glucose. If blood sugar drops too low, the brain is starved of its primary fuel, causing dizziness.
Rapid change in position	Standing up quickly after lying or sitting down (e.g. after stretching) can cause a sudden drop in blood pressure.

How to prevent light-headedness:

• Perform a proper cool down to maintain blood flow and prevent blood pooling.
• Stay hydrated before, during and after exercise.
• Consume carbohydrates to maintain blood sugar levels.
• Stand up slowly after floor-based exercises or stretches.

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3. Nausea

Nausea (feeling sick) can occur during or after intense exercise. This is relatively common and is usually temporary.

Causes of exercise-related nausea:

Cause	Explanation
Blood redistribution	During exercise, blood is redirected away from the digestive system to the working muscles. This can cause nausea, especially if the athlete has eaten recently.
Lactic acid build-up	High levels of lactic acid in the blood can trigger nausea. This is common after very intense interval training or sprint sessions.
Dehydration	Fluid loss can cause the stomach to feel unsettled.
Heat stress	If the body overheats during exercise, nausea can be a symptom.
Excessive or rapid food intake before exercise	Eating a large meal too close to exercise can cause nausea when blood is diverted away from the stomach.

Nausea in sport:

It is common to see athletes feeling nauseous after finishing an 800 m race (one of the most intense events) or after completing a high-intensity interval training (HIIT) session. The 800 m requires near-maximal effort for approximately two minutes — long enough for massive lactic acid accumulation but too intense to be aerobic.

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4. Delayed Onset Muscle Soreness (DOMS)