[Music] hi and welcome back to three size lessons Cole you K by the end of this video you should be able to describe what happens in the body during exercise and if you're a higher tier student you should then be able to describe what's meant by the oxygen debt now as we saw in the last video humans need energy for movement to keep warm and for chemical reactions to build larger molecules all of the energy we need is provided by respiration as we saw there were two types of respiration these are air robic and anaerobic now when were relaxing like this we don't need a great deal of energy and that's because we're not moving but you in exercise the body needs a great deal of energy for muscle contraction and the body has to react to the increased demand for energy now because the body needs more energy air robic respiration increases this means that the body cells require more oxygen so to provide this extra oxygen both with the breathing rate and the breathing volume increase in other words we breathe more frequently and we take deeper breaths this gets more oxygen into the bloodstream the heart rate also increases to pump this oxygenated blood around the body now there's a big problem here sometimes not enough oxygen can be supplied to the muscles especially if we're exercising hard at this point anaerobic respiration now takes place in the muscles now as we saw in the last video during anaerobic respiration the oxidation of glucose is incomplete this leads to a buildup of the chemical lactic acid during long periods of vigorous activity the lactic acid causes the muscles to become fatigued this causes the muscles to stop contracting efficiently at this point the body has to remove the lactic acid from the muscles and this creates a condition called the oxygen debt if you're a foundation student you can stop watching now but if you're a higher tier student you need to keep watching so as we've seen during vigorous exercise anaerobic respiration produces lactic acid in the muscles the lactic acid is transported out of the muscles by the blood the lactic acid is then taken to the liver and it's converted back to glucose in a series of chemical reactions now reacting with the accumulated lactic acid and removing it from the cells requires oxygen so the oxygen debt is the amount of extra oxygen the body needs after exercise to deal with the accumulated luck take acid that's why people continue breathing rapidly for some time after finishing exercise remember you're fine plenty of questions on exercise in my vision workbook and you can get that by clicking on the link above ok so hopefully now you should be able to describe what happens in the body during exercise and if you are higher to your student you should then be able to describe what's meant by the oxygen debt [Music]