2.40 describe experiments to investigate the effect on exercise on breathing in humans

2.40 •sit for five minutes, then count the number of breaths for one minute

        •do four minutes of exercise and as soon as you stop count your breaths for a minute

        •results show that exercise increases breathing rate, because your muscles respire more

                  •they need to be supplied with more oxygen and have more carbon dioxide removed, so your breathing rate increases

       

        •you need to control all the variables e.g controlling time exercising using a stopwatch, temperature using air conditioning / thermostat etc.