There are few strength training exercises as old-school as kettlebells. Traditional kettlebells, resembling a black cannonball with a handle attached, date back to czarist Russia and are more often associated with side-show strongmen than modern weight-training techniques.

But kettlebells are experiencing a resurgence of late. While some people continue to dabble with the traditional cannonball design, a redesigned, modernized kettlebell is becoming a new tool in functional fitness training.

Tom Sliney, who owns the CORE personal training studio in Bend with his wife, Tammy, added kettlebells to the studio’s array of weight machines and free weights last year.

”Kettlebells are an old exercise tool,” he says. ”We’ve taken that exercise tool, taken what’s good with it, improved it and now you can start doing a number of other exercises with it.”

Kettlebells are particularly effective in functional training, a type of strength conditioning based on the notion that bodies operate in free space not supported by a weight bench or mechanical devices. Weight training machines isolate particular muscles or muscle groups and can be helpful particularly for people with limitations that make other forms of strength training difficult.

Functional fitness training, on the other hand, works both the major muscles and the smaller stabilizer muscles that keep the body in proper position without additional support. Functional training incorporates strength, balance and core training.

The design of the kettlebell helps facilitate that goal. Modern kettlebells are essentially a weight connected to a swiveled handle. That handle allows the weight to hang straight down regardless of your hand position, and the instability forces the body to use its smaller stabilizer muscles to hold the position or even maintain balance.

It’s easy to see the difference kettlebells make with a simple demonstration. Take a dumbbell and lift it up above your head extending the arm, a standard one-arm, overhead press. With a reasonable weight, it’s easy to keep the weight still. But with the same exercise with a kettlebell, even with a lighter weight, the arm and hand must constantly shift and adjust to keep the weight in position.

Sliney says he generally starts clients on weight machines first to build up the strength they need to train safely with weights in free space. Clients then proceed to free weights and kettlebells.

”If you goal is to develop functional strength, I think the kettlebell is the better exercise,” Sliney says. ”Most of the exercises we do are going to involve core strength to try to keep your body in alignment.”

Kettlebell exercises can resemble standard weight training lifts or incorporate techniques from yoga, Pilates or ploymetrics. Some trainers use kettlebells to better approximate movements specific to individual sports than could be done with free weights or machines.

Jeff Browning, a 34-year old graphic designer and an ultramarathoner from Bend, has been training at CORE for two years. He says the swiveled handle of the kettlebell forces him to conduct training in the proper position.

”They really make you concentrate on strict form otherwise you get slapped,” he says. ”Certain lifts, like rows, you’ll pop yourself in the head if you don’t use really strict form.”

He believes the kettlebells offer runners a way to work more than just the major muscles.

”With running, it’s really important to be very balanced and stable,” he says. ”Kettlebells work all the muscles you normally couldn’t work with dumbbells or regular machines. They work the little, tiny intricate stabilizer muscles.”

Steve Emery, a 42-year-old businessman from Bend has been impressed by the workout kettlebells provide.

”It’s intense because you don’t get a rest point. If you’re using a traditional dumbbell or machine, the rest of your body is typically resting outside of the muscle groups you’re (working),” he says. ”The way these hang, especially with the swivel, you don’t get a rest period. It really ups the intensity level.”

Emery says it’s important for him to get as much out of his limited work out time as possible, and kettlebells help to ensure there is no wasted time.

”I don’t care who you are, when you’re working out, you get a little bit fatigued, you want to cheat a little bit,” he says. ”This isn’t going to let you. And those results pay off.”

And because the kettlebells demand continued effort from all parts of the body, a workout can be much more demanding. Emery says he can feel the difference.

”I’ve got fairly strong legs,” he says. ”But after a kettlebell workout the other day, my legs were really sore. It’s pretty impressive.”