The term intenisty in fitness is part of the F.I.T.T. principle. FITT stands for frequency, intensity, time, and type of exercise. Intenisty denotes how hard you work during exercise and it is correlated with the breathing and heart rate. According this definition, the statement that increased intensity refers to how greatly one increases the level of training is false. How greatly one increases the level of training denotes the progression principle in fitness.
Tolerance can in fact cause an overdose, because the greater tolerance you can get the more of a certain substance your body will need eventually leading your body to take more than it can handle leading to overdose and death.
