Dumbbells are one of the smartest ways to do a total-body workout if they are used correctly. One of their best traits is that they are compact and easy to store, making them an excellent conditioning tool if you have only a limited amount of space and time for exercise. For best results, invest in two sets of dumbbells: one relatively light, and the other heavy enough to cause fatigue at the end of the allotted time frame for each circuit.
Try these kettlebell exercises for core strength from Smarter Workouts.