for Penny:
Why can’t I just do cardio to stay
healthy or lose weight (stay in shape)? Why do I have to do weight training or
“weight-bearing” exercises?
Strength training burns more fat and calories, and build more lean muscles (which also burns fat). Muscle tissue is
more “active” than fat tissue, with each pound burning about 30
calories a day just to stay “alive”. So even if you’re sitting on the
couch or stuck at your desk for eight hours a day, the extra lean muscles you
develop will burn more calories, helping you keep weight off for good.
It has been proven that even though you
are burning calories during your cardio session, with strength training you
don’t only burn calories during the workout, but you can burn more even after
the workout, due to the “after-burn” effect. This means that for up to 24
hours or so after the workout has ended, calories are being burned at an
elevated level for recovery, blasting more fat even while you’re at rest.
Also, without regular strength training
(at least twice a week) to build and maintain lean muscle mass, your body’s metabolism cools down over time and burns fewer and fewer calories. This
doesn’t give you much leeway when it comes to enjoying your “fun” foods. Not to
mention, without strength training, don’t be surprised if you end up with a
not-so-tight, not-so-flattering body composition. 

Another important thing to remember:
Putting pressure on muscles not only makes them stronger, but it also puts
pressure on bones which forces your bones to make new cells, building bone
density. This is a good way to avoid osteoporosis (degeneration of bones). So
learn to use the machines or dumbbells properly and make it a part of your
lifestyle regimen. Heck, you don’t even need equipment; bodyweight exercises
such as squats, pushups and planks will do the trick! (As long as you’re doing
them regularly.)