Variety is the spice of life, just as your mind gets bored with the same old thing all the time your body does the same. When your body gets bored you hit a plateau in your fitness goals. Changing your routine allows you to continue moving forward toward reaching your fitness goals.
Targeting certain areas is not the best idea especially when it comes to toning and weight loss. Working the total body is the best approach to leaning out (in both of these cases “calories burned” is a major factor, working the total body maximizes your caloric burning potential) so you can obtain the “six pack”/ “washboard abs”, toned arms, legs, etc.
