Resistance
Also known as STRENGTH training, resistance is the key to any progression in getting or staying fit and developing stronger muscles. Muscle burns calories faster than fat, and is the key to a good metabolism. It’s also important to keep up our muscle mass through training, as it can decrease yearly in small amounts after the age of about 20.
For those concerned about 'looking too muscley', strength training will NOT necessarily buff you up, as it takes many different aspects such as genetics, the intensity of your training, any supplements you take and more.

So if you want..
> To Boost Your Metabolism
> Stronger connective muscle tissue to help prevent injuries
> Improved Blood Pressure
> Improved Bone Density
> Improved energy levels - which can also help raise alertness.

Then resistance (strength) training is vital in your exercise program !