Effects of exercise IGCSE Biology Whats happening in

Effects of exercise IGCSE Biology

What’s happening in your muscles? In normal conditions our body uses oxygen to fully break down glucose in aerobic respiration: 2900 k. J Glucose + oxygen energy + water + carbon dioxide During hard exercise, muscles use up a lot of glucose to get enough energy. Sometimes not enough oxygen can get to the muscles so anaerobic respiration (without oxygen) takes place and Lactic acid forms.

Why does this happen? During vigorous exercise you need a lot more energy and get it by: Å Breathing deeper and faster Å Dilated blood vessels deliver more oxygen to muscles (and increased heart rate) Å When at maximum, body starts to respire anaerobically (making lactic acid), but Muscle fatigue results from a lack of oxygen and a build up of lactic acid.

Investigating exercise’s effects on pulse rate Pupil Activity Copy this table into your notes: Beats per min Sitting down Straight after exercise 2 min after exercise 1. Measure your resting pulse rate over 1 minute. 2. Exercise for 2 minutes. 3. Measure pulse rate again. 4. Wait for 2 mins. 5. Measure pulserate again. 6. How has the pulse rate been affected by exercise? 7. Why does your body do this in response to exercise?

Anaerobic respiration Instead of glucose forming CO 2 and H 2 O, it is broken down without oxygen into an intermediate, lactic acid, giving less energy: 120 k. J Glucose Lactic acid + energy BUT lactic acid accumulates in the muscles causing muscle fatigue and cramps. To avoid damage to cells it has to be broken down fully to CO 2 and H 2 O immediately after the exercise has finished. This needs more oxygen (oxygen debt)…

Oxygen debt In order to get the extra oxygen to 'pay back' the debt, the body continues to breathe deeply for some time after vigorous activity has ceased. When all the lactic acid in the muscles is broken down the oxygen debt has been repaid and normal aerobic respiration resumes. Recovery time is the time taken to return to normal levels of pulse rate, breathing rate and lactic acid. It can be used as an indication of physical fitness because a fit person will recover faster than an unfit person- their breathing and pulse will return to normal in a shorter time.

How does training help? With exercise the pulse rate, breathing rate and lactic acid level rise less in an athlete than in an untrained person because training and fitness makes aerobic respiration more efficient by: improving the efficiency of the lungs and circulation. This means less of an oxygen debt is built up during exercise. Hence, less extra oxygen is needed afterwards to break down the lactic acid.

Recovery time is the time taken to return to normal levels of pulse rate, breathing rate and lactic acid. It can be used as an indication of physical fitness because a fit person will recover faster than an unfit person- their breathing and pulse will return to normal in a shorter time. Only elite athletes reach top 3

Heart volume Training summary Volume blood pumped Explain the relationship between the effects of training & recovery time. Resting pulse rate Fitter person has faster recovery because: Lung volume Improved circulation to muscles Volume oxygen per breath Breathing rate