Exercise & Metabolism - Bodily Responses to Exercise (GCSE Biology)
Bodily Responses to Exercise
Aerobic Respiration and Exercise
Normal Changes During Exercise
- When you exercise, respiration increases. The rate of respiration increases to supply the increased amount of energy the muscles need to contract.
- This means respiring cells need more oxygen. Oxygen is a requirement for aerobic respiration, so if cells are respiring more they need more oxygen.
- Breathing rate and breath volume increases. To increase the amount of oxygen in the blood, breath volume and breathing rate rise.
- Heart rate increases. The number of heart beats per minute (heart rate) increases to take oxygen to the respiring cells and remove the waste product CO₂.
Anaerobic Respiration in Exercise
- Anaerobic respiration can occur in intense exercise. Intense exercise (e.g. running for the bus) can mean that the body cannot deliver oxygen to the muscles fast enough – leading to anaerobic respiration.
- Lactic acid builds up in anaerobic respiration. Anaerobic respiration during exercise leads to a build up of lactic acid, which can cause pain. This is what happens when we have a ‘stitch’.
- The build up of lactic acid causes an oxygen debt. When lactic acid builds up due to anaerobic respiration, it causes an oxygen debt after exercise has stopped.
Oxygen Debt and Lactic Acid
Oxygen Debt
Oxygen debt is the additional oxygen you need to remove the build up of lactic acid.
- After exercise stops, lactic acid will be leftover. Even after stopping exercising, there will be lactic acid in the cells. This will need to be reacted with oxygen to form CO₂ and water.
- Therefore BR and HR stay high after exercise. To deliver the oxygen to the cells, breathing rate will stay high to increase oxygen in the blood, and heart rate will stay high to deliver oxygenated blood to the cells.
- HR and BR only fall when lactic acid levels fall. When lactic acid levels fall, there is no longer oxygen debt and so the heart rate and breathing rate falls.
- The liver helps to break down lactic acid. The high heart rate also allows the blood to transport lactic acid from the muscle cells to the liver. Here the lactic acid is broken down using oxygen in aerobic respiration and made back into glucose.
Muscle Fatigue
- Muscle fatigue can occur if exercise continues. Exercising for a long period can cause muscle fatigue, reducing their effectiveness and reducing the strength of contractions.
Investigating the Effect of Exercise
Measuring Heart and Breathing Rates
- Heart rate – by measuring your pulse at your wrist, you can find the beats per minute.
- Breathing rate – by looking at how many times your chest rises, you can count the number of breaths per minute.
Calculating Cardiac Output
Cardiac output is the volume of blood pumped out of a ventricle in the heart per minute. You can calculate it using the following equation:
cardiac output = heart rate x stroke volume
- Heart rate = number of beats per minute (explained above)
- Stroke volume = volume of blood pumped out by the ventricle in one contraction
You can also calculate heart rate and stroke volume by rearranging the equation or using the formula triangle.
Example:
A person has a cardiac output of 5,000 cm³/min and a heart rate of 100 beats per minute. Calculate their stroke volume.
- Rearrange the equation to calculate stroke volume.
Stroke volume = cardiac output / heart rate - Substitute the values and calculate.
Stroke volume = 5000 / 100
Stroke volume = 50cm³
Investigating Effect of Exercise
- Measure HR and BR at rest. In pairs, you could take your pulse and breathing rate without exercise. You can later compare this with the values during exercise.
- Do 10 star jumps, and measure again. You could then do 10 star jumps and measure it again.
- Do 50 start jumps, and measure again. You could then do 50 star jumps and measure it once more. Measuring values after more intense exercise will show the effect of this increased effort on heart rate.
- Measure again after 3 minutes of rest. Measuring after 3 minutes will enable you to consider the oxygen debt, and see if the heart rate has fallen back to its normal level.
- Repeat the experiment with more individuals. You can take all the results from the whole class and find the average heart and breathing rate each time. By taking a mean, it reduces the chance of random errors in your results.
- Plot the mean values on a bar chart. The average values could be plotted on a bar chart to show the trend. Plotting the chart will show that increasing the intensity of exercise increases the breathing rate and pulse.
- Analyse the oxygen debt. Consider the values recorded after 3 minutes of rest. If the heart and breathing rate are still above the rate at rest, it shows that the cells are still breaking down lactic acid – which is the idea of oxygen debt.
FAQs
Metabolism is the process in which the body converts food into energy. It helps in maintaining various bodily functions like breathing, pumping of blood and digestion.
Exercise increases metabolism as it increases the rate at which the body burns calories. This leads to an increase in energy expenditure and helps in weight loss.
During exercise, the body experiences various physiological responses, such as increased heart rate, breathing rate, and body temperature. This happens to meet the increased demand for oxygen and energy by the body.
No, exercise only temporarily increases metabolism. However, regular exercise can help in maintaining a higher metabolism, leading to long-term benefits such as weight loss and improved overall health.
An increased metabolism helps in burning more calories, leading to weight loss. It also helps in improving cardiovascular health, increasing muscle mass, and boosting overall energy levels.
The effect of exercise on metabolism can be seen almost immediately. However, the extent of the increase in metabolism depends on various factors, such as the type, intensity and duration of exercise.
Both strength training and cardio have their own unique benefits for increasing metabolism. Strength training helps in building muscle, which in turn boosts metabolism. On the other hand, cardio helps in burning calories and improving cardiovascular health.
Yes, metabolism can decrease with age. This is due to a decrease in muscle mass, hormone levels and overall physical activity. However, regular exercise can help in maintaining a higher metabolism and combat the effects of aging.
Yes, certain foods, such as protein-rich foods, green tea, and spicy foods, have been known to increase metabolism. However, it is important to remember that a balanced diet and regular exercise are key to boosting metabolism and maintaining overall health.
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