There’s nothing quite like slamming a medicine ball into the ground. If you haven't yet experienced it, we suggest you remedy that immediately. It's an easy and effective way to build muscle, rev your metabolism and increase your overall strength. Oh, and because it makes you feel like a badass, it's also a pretty good stress-reliever too. And right now, couldn't we all use a workout that doesn't require a lot of equipment and squashes our anxiety?

These weighted sand-filled balls—called everything from medballs to slam balls—are one of the most versatile tools in the gym. Use them indoors or out, as gently or violently as you like. It's a simple piece of equipment (just a heavy ball) but it has the ability to fire up a myriad of muscles while challenging your body's natural biomechanics. This is one of those training tools that the more you use it, the more ways you find to work it into your routine.

Of course you can simply hold the balls to add weight while you do crunches, twists and Superman extensions to work your abs and core. You can raise the ball over your head and slam it to the ground. The slam ball's explosive namesake exercise makes for a heart rate-spiking compound exercise. Here are three more moves to master and a few trainer-recommended balls to buy.