When the muscles start to work, they need more oxygen so the respiratory system responds by getting more oxygen into the lungs. The blood carries greater amounts of oxygen and the heart responds to pump more oxygenated blood around the body.

These effects are shown in the table:

After exercising, the muscles need to rest, adapt and recover. There is a risk of injury if the body is not rested for long enough after exercise. This concept can be better understood by studying the Principles of training.

During exercise, the cardiovascular system redistributes the blood so that more of it goes to the working muscles and less of it goes to other body organs such as the digestive system. This redirection of blood flow is caused by a mechanism (or process) called the vascular shunt mechanism. It works a little bit like a railway terminal, where trains are directed on to some tracks and stopped from travelling on to others. The blood vessels allow lots of blood to travel to the working muscles but they don’t allow much to travel to other organs. When the muscles stop working, the blood distribution returns to its normal route.

Warming up before sport allows the body systems to make all these changes gradually, so they are fully prepared for the stresses placed upon them during the activity.

Question

Why is a person less likely to strain a muscle if they have warmed up before taking part in exercise?

Answer

Warming up increases the temperature of the muscles which makes them more pliable and therefore more likely to stretch rather than tear.

 

Question

A badminton player is playing a point in a match. What changes take place in the heart during the rally?

Answer

Heart rate increases (more beats per minute), stroke volume increases (ventricles pump out more blood each beat), cardiac output increases (more blood pumped out per minute).

The immediate effects of exercise tend to be gone within a few minutes of exercise ending. However there are other side effects that tend to last a little longer.

Tiredness and fatigue can be experienced in the days after heavy training or a big competition. This can be both physical but also mental tiredness. Sleeping well after training is therefore very important and can be thought of as part of an excellent recovery.

Light-headedness can be experienced in the hours after training and is usually a sign of either dehydration or low energy stores or both.

Nausea is a feeling of sickness that can take place during the hours and even days after very intense physical exercise. Athletes need to try to refuel even if they feel a little sick.

Delayed Onset of Muscle Soreness (DOMS) occurs when muscles experience pain for 24-48 hours after intense exercise due to microscopic tears in the muscle fibres. DOMS typically follows a change in training or performance intensity and the muscles need to be rested while in this condition to avoid injury.

Long term effects of exercise on the body systems

Taking part in regular exercise or training around three times per week for six weeks will lead to adaptation of the body systems that are used or trained. This has the effect of increasing performance in that type of exercise or sport and is often beneficial to general health and everyday life.

Resistance training increases strength

Aerobic training increases aerobic endurance

 

	Long term effects of exercise	Type of training
Cardiovascular system	Cardiac hypertrophy; increased stroke volume (SV) at rest and during exercise; decrease in resting heart rate (HR); increase in cardiac output (Q); capillarisation at the lungs and muscles; increase in number of red blood cells	Aerobic activities (lower intensity, longer duration) produce these effects most
Respiratory system	Increased tidal volume (TV), minute ventilation (TE) and vital capacity; increased number of functioning alveoli; increased strength of the respiratory muscles (intercostals and diaphragm)	Aerobic activities (lower intensity, longer duration) produce these effects most
Energy system	Increased production of energy from the aerobic energy system; increased tolerance to lactic acid; faster recovery rate; increased aerobic capacity	Aerobic activities/training; anaerobic training; general effect
Muscular system	Muscle hypertrophy; increased strength of tendons and ligaments; increased muscular strength; increased muscular endurance; increased speed of contraction; increased resistance to fatigue	Resistance/weight training; general effect; aerobic activities/training; anaerobic/speed training
Skeletal system	Increase in bone density and strength; increased flexibility	Resistance training; weight bearing activities; flexibility training/stretching

Cardiac hypertrophy

Hypertrophy means an increase in size, so muscle hypertrophy means the muscles get bigger. If you weight train regularly doing biceps curls, your biceps will show muscle hypertrophy. Cardiac hypertrophy is where the ventricle wall gets larger or thickens as a result of exercise.

The muscle wall of the left ventricle increases in size, meaning it is able to pump out more blood during each contraction which increases the stroke volume. As stroke volume is increased, resting heart rate decreases but cardiac output (Q) remains the same as SV × HR = Q.

Capillarisation

Capillarisation is the process where new capillaries are formed. Capillarisation takes place at the alveoli in the lungs and at the skeletal muscle. This has the effect of increasing the amount of oxygen that can be transferred to the working muscles as well as increasing the amount of carbon dioxide that can be removed.

Effects of exercise on the cardiovascular system

Changes to heart rate during exercise

Heart rate is measured in beats per minute (bpm). During exercise the heart rate increases so that sufficient blood is taken to the working muscles to provide them with enough nutrients and oxygen. An increase in heart rate also allows for waste products to be removed.

Change to stroke volume during exercise

Stroke volume increases which means more blood is pumped out of the heart each time it contracts.

Changes to cardiac output during exercise

At rest a person’s cardiac output is approximately 5 litres per minute, while during exercise it can increase to as much as 30 litres per minute as both their heart rate and stroke volume increase.

Changes to blood pressure during exercise

As exercise increases, cardiac output (Q) also increases. This has the effect of increasing blood pressure.

A typical blood pressure reading for a person at the start of exercise would be around 160/85 mmHg.

Effects of exercise on the cardio-respiratory system

The cardio-respiratory system works together to get oxygen to the working muscles and remove carbon dioxide from the body.

During exercise the muscles need more oxygen in order to contract and they produce more carbon dioxide as a waste product. To meet this increased demand by the muscles, the following happens:

Breathing depth (tidal volume) and rate increase – this gets more oxygen into the lungs and removes more carbon dioxide out of the lungs.

The graph shows that as a person goes from rest to exercise, their tidal volume increases.

Heart rate increases – this increases the rate that oxygen is transported from the blood to the working muscles and carbon dioxide is transported from the working muscles to the lungs.

This graph indicates the following:

• the person’s resting heart rate is around 60 bpm
• at 8 minutes, just before taking part in exercise their heart rate increases – this is called the anticipatory increase in heart rate which occurs when a person starts to think about taking part in exercise
• at 10 minutes the person starts to take part in exercise and there is a steep increase in heart rate which reaches 145 bpm at 13 minutes
• the heart rate remains high during exercise
• when the person stops taking part in exercise the heart rate decreases

Bibliography: BBC – Education

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