Exercise intensity depends on an individuals physical status, Sex , weight of an individual. So its a total concern of these things upon which the exercise intensity depends. To measure exercise intensity there are various tests like 12 min walk test, VO2 max test etc which will measure the lung capacity and thus will measure the endurance of your heart and also we need to calculate the maximum heart rate by subtracting your age from 220 which will give you max heart rate .We should not exercise more than the maximum heart rate.So.exercise intensity depends upon both parameters , Maximum heart rate and VO2 max.