Armed with an altruistic aspiration to please his clients, Jeff Estopellan set out to bring kettlebells, the ancient Russian exercise tool, to Chicago-area stores.

“I just wanted to fulfill their need and maybe make a little bit of money along the way,” said Estopellan, the director of retail operations at Forest Park-based Fitness Factory Outlets. The company manufactures and sells fitness products – including kettlebells – to Chicago-area retailers.

Estopellan’s plan succeeded. Since they first became available at local stores in 2006, kettlebells have seen a rapid rise in popularity, according to sellers of the orb-shaped, cast-iron weights.

Kettlebells help boost metabolism, burn fat, build endurance and develop strength, said Arturas Kolgovas, a Chicago-area kettlebell trainer.

Kettlebells date back to 18th century Russia, where strongmen and the military used them as a training tool. In the early part of the 1990s, scads of American exercise enthusiasts started to use them, too. But with the introduction of exercise machines the popularity of kettlebells waned. And until recently, they laid dormant in the United States.

Minnesota-based Dragon Door Publications Inc. reintroduced kettlebells to the American public in 2001, Kolgovas said.

Dragon Door CEO John Du Cane teamed with Pavel Tsatsouline, a fitness trainer who formerly trained the Soviet Special Forces, and brought kettlebells to market in the U.S. But Du Cane said neither he nor Tsatsouline expected the enormous popularity kettlebells have enjoyed.

Once Estopellan realized the imminent resurgence of kettlebells in the Chicago area, he ignited what he called an “astronomical” rise in sales for these hunks of metal that look like cannonballs with handles.

“In the Chicagoland area two years ago, there were no kettlebells,” he said. “Customers had only one option – to buy them online through Dragon Door. They had a monopoly on the market. So we introduced them and now people have other options.”

Fitness Factory’s kettlebells sales surged from $630 in December of 2006, the first month the company offered them, to $266,000 by the end of 2007.

“It was mind-boggling,” Estopellan said. “Three months out of that first year, we were out of stock because we couldn’t produce them fast enough.”

In the first five months of this year, kettlebell sales have climbed to $271,000. If sales keep up at that pace, by the end of this year Fitness Factory would have wholesaled more than $650,000 in kettlebells alone, a 144 percent increase from 2007.

Estopellan said that total will translate to between $1 million and $1.2 million in revenue for the retailers that buy kettlebells from Fitness Factory and sell them to consumers.

As a percentage of sales over the past two years, kettlebells now trail only pilates, said Monty Kilburn, vice president of marketing at Power Systems Inc., a fitness equipment vendor.

The increase in popularity opened the door for more distributors, Estopellan said, and many of them, including his own company, are leveraging overseas manufacturing prowess in countries such as China to make kettlebells.

As a result, kettlebells prices have dropped from more than $7.50 per pound a few years ago to as low as $2 per pound today. For example, a 12 kilogram (approximately 24 pound) kettlebell sold for as much as $200 in 2006. Today, one can be purchased for $50. Kolgovas said American-made kettlebells by companies like Dragon Door are more expensive but better in quality.

Considering that the $5 billion market for physical fitness equipment is growing, according to Global Industry Analysts Inc., the demand for kettlebells – whether U.S. made or not – is also expected to rise.

“It’s just the tip of the iceberg,” Du Cane, the CEO of Dragon Door, said. “I don’t have any sense that it’s a fad.”

In addition to the high demand for kettlebell training, a whole market for kettlebell-related products and services has developed, including DVDs, books, magazines and Web sites. For example, Dragon Door’s Web site receives approximately 350,000 unique visitors per month and 120,000 people bought its magazine, Du Cane said.

What’s more, kettlebells are difficult to train with if a person doesn’t learn from a trained instructor, said Shawn Cull, a Chicago-area kettlebell instructor. That fact has given rise to a swath of kettlebell certification programs around the U.S.

“It’s a bit of a niche market,” said Chicago fitness trainer Clint Phillips. “People have started to specialize in kettlebells as a marketing hook that sets them apart.”

Diane Russell, manager at Forest Park’s Evolution Fitness, said that her gym has seen only “a little” surge in the popularity of kettlebells. According to Russell, it has mostly been men who have found the wide variety of exercises and greater mobility allowed by kettlebells beneficial.

Increasingly, sports teams are incorporating kettlebell exercises into their workouts.

“We had specific exercises that we thought the kettlebell spoke better to than anything else we were using,” Chicago Bears strength and conditioning coach Rusty Jones said.

Jim Zielinski, the head strength and condition coach at the University of Illinois at Urbana-Champaign, said he adopted kettlebells this fall because they enable “more functional and explosive movements.”

But surprisingly, said Du Cane, the core kettlebell customer in the U.S. is not a professional athlete, bodybuilder, or even mixed martial artist. It is a 35- to 55-year-old woman looking to firm up.

“Seventy to 80 percent of the people in our classes – even if they are run by grizzled ex-marines – are now women,” Du Cane said.

Part of the disparity noted by Du Cane could be attributed to machismo. Generally, said Cull, men are less likely to seek help in adopting new exercises into their routine.

“Women are the ones who pay for classes, for trainers and who tend to be a little more open-minded,” Cull said. “Whereas men think they know how to do it.”

Forest Park Review intern Jacob Boyer contributed to this report.