Question

Bradley decides one day to run a marathon without any training. After ten minutes has elapsed and Bradley has run half a mile, he begins to get cramps in his thighs. He is also breathing very rapidly. What is causing the cramps on Bradley's legs?

Answer 1

The most likely cause of cramps in Bradley's thighs would be the build up of lactic acid. This is a side effect of longer and strenuous activity during which you continouosly tax your body - or rather your muscles where they would need a lot of energy to properly function. 

Answer 2

The cramps can be caused due to anaerobic respiration in the muscles and lactic acid formation.

During intense physical activity the muscles become deprived of oxygen, in this condition, anaerobic respiration takes place in the muscle cells causes the formation of the lactic acid.

The physical training increases the strength of the muscles, which can help the muscles not to get tired easily. that is why, physical training is required before any marathon.