Cardio is great for you, but it's not the end all and be all of healthy exercise. Strength training, no matter how young or how old you are, is also a critical component. So much so that health experts from prominent organizations like the American College of Sports Medicine and the American Heart Association are releasing new guidelines and recommendations regarding strength training -- all adults are encouraged to work all major muscle groups twice a week, at least.

Need some tips? Here's a great list of tips for young and old alike -- it's never too late to get started!