Feb. 12, 2010 -- A centuries-old piece of cast iron exercise equipment may be the latest fitness craze for would-be strongmen, but a new study shows it still delivers the goods.
The cannonball-shaped cast iron orbs called kettlebells were originally developed by Russian strongmen in the early 1700s to quickly build strength, endurance, balance, and flexibility. Once relegated to a dusty corner of the weight room, researchers now say kettlebells are experiencing a resurgence in popularity; kettlebell-themed fitness classes are now being offered in gyms across the country.
But perhaps they are best known for helping bulk up the physique of actor Gerard Butler, who used kettlebell workouts to train for his role of King Leonidas of Sparta in the movie 300.
Although many claims have been made about the effectiveness of kettlebell workouts, researchers say this is the first modern study to examine the fitness benefits of kettlebells.
Kettlebell enthusiasts "make these all-encompassing claims about increasing your muscular strength, endurance and aerobic capacity with kettlebells, like if you do this that's all you need to do," says researcher John Porcari, PhD of the University of Wisconsin, La Crosse Exercise and Health Program, in the report, published in ACE FitnessMatters. "So we wanted to look and see how much of an aerobic workout you really do get and how many calories you burn."
The study involved 10 men and women between the ages of 29-46 who performed a typical kettlebell workout by doing kettlebell swinging and lift exercises to a certain rhythm during a 20-minute period. All were experienced with the use of kettlebells.
The participants' fitness levels were measured before and during the workout by measuring heart rate, oxygen consumption, and blood lactate.
The results showed that the average participant burned about 20 calories per minute during the kettlebell workout, which equates to 400 calories during a typical 20-minute kettlebell workout.
Researchers say that's equivalent to running a six-minute mile or cross-country skiing uphill at a fast pace. They credit the rapid calorie burn to the interval training format of kettlebell workouts.
In addition, the researchers write that the participants achieved exercise heart rate and maximum oxygen uptake, suggesting that kettlebells provide a more intense workout than standard weight lifting.
"This is good news for people who are looking for a very good resistance-training workout that will also help them lose weight," says researcher Chad Schnettler, MS, also of the University of Wisconsin, La Crosse Exercise and Health Program, in the report. "For people who may not have a lot of time, and need to get in a workout as quickly as possible, kettlebells definitely provide that."