A 'kettlebell' is a traditional Russian cast iron weight that looks like a cannonball with a handle. Kettlebell lifting has been used for many years in the Russian Special Forces to simultaneously develop strength and flexibility. The ability of kettlebell training to develop agility, stamina, endurance, conditioning and strength has also been realised by the US military who have incorporated it into their training. Kettlebell training has since taken off amongst people from all walks life including martial artists, athletes and fitness fanatics alike.