The kettlebell is a cast-iron weight (resembling a cannonball with a handle) used to perform ballistic exercises that combine cardiovascular, strength and flexibility training.
By their nature, typical kettlebell exercises build strength and endurance, particularly in the lower back, legs, and shoulders, and increase grip strength. The basic movements, such as the swing, snatch, and the clean and jerk, engage the entire body at once, and in a way that mimics real world activities such as shoveling or farm work.
Unlike the exercises with dumbbells or barbells, kettlebell exercises often involve large numbers of repetitions. Kettlebell exercises are in their nature holistic; therefore they work several muscles simultaneously and may be repeated continuously for several minutes or with short breaks.
This combination makes the exercise partially aerobic and more similar to High-intensity interval training rather than to traditional weight lifting.
The movements used in kettlebell exercise can be dangerous to those who have back or shoulder problems, or a weak core. However, if done properly they can also be very beneficial to health. They offer improved mobility, range of motion and increased strength.