Whether you've vowed to get in shape in the new year or just bored with your current gym routine, get your hands on a kettlebell. These intimidating cast-iron cannonballs originated a few centuries ago in Russia. Which makes sense, considering it looks like the kind of workout your grandfather did—picking up heavy shit and moving it around. Simple. Fast. Effective. Really effective. It will work muscles you never knew you had and help you shred fat while providing real flexibility and the cardio benefits that'd rival a treadmill. To start off, find a kettlebell that you can lift and hold at least ten times and begin with this simple work out.