Sterling resident Jon Aust didn't take up karate until he was in his early thirties, but at 41, he already has a black belt.

"This sport just fits [me] perfectly," he said. "You've got to have flexibility, speed and quickness . . . and mentally you've got to be able to absolutely focus."

Those characteristics have not only helped Aust in karate but also have helped him grow his Sterling-based company, Network Access Solutions, at a frenetic pace. In fact, the company announced yesterday that it will have to move outside Loudoun County to accommodate its rapidly growing work force and a network operations center. The company will move its headquarters to Herndon in March but maintain a small Loudoun presence, officials said.

Aust founded Network Access Solutions, which provides Internet-access services to businesses, in 1995, after nearly 20 years in the telecommunications industry. In the past year, the company has grown from 35 employees to more than 400.

NAS, which raised $84 million when it went public in June, has gained momentum on Wall Street lately by penning deals with such companies as Cisco Systems Inc. The Cisco partnership was announced last week and will allow NAS to offer a broader array of services. More important, the association with the networking powerhouse will raise NAS's marketing credibility. On news of the deal, NAS's stock price more than doubled. The stock was trading in the $20 to $25 range earlier this week on the Nasdaq Stock Exchange.

This week, NAS is expected to announce a relationship with Intermedia, which would expand NAS's regional coverage. NAS could connect a customer in the mid-Atlantic area, for example, to the NAS network and then use the Intermedia network to connect to the customer's branch offices in, say, Dallas.

NAS's original mission was to provide digital subscriber line service. Digital subscriber lines (DSL) deliver high-speed Internet access over regular telephone lines. The service is particularly appealing to smaller companies because it is a cheaper alternative to other types of connections.

NAS competes with such companies as Covad Communications Inc., of Santa Clara, Calif., which recently announced that it would locate an East Coast hub in Prince William County. However, Aust said, NAS differs from Covad and other competitors in a couple of ways.

First, "we decided to focus on the regional marketplace," Aust said. His company's network will soon have 85 percent coverage from Virginia to Maine rather than spotty coverage nationwide. Areas of coverage are significant to businesses that need to communicate with their branch offices and customers over such networks.

Aust said he soon will be looking into expanding into other states, starting with the Intermedia arrangement. He also could connect his network with SBC Communications, a telecommunications company that invested $11 million in NAS during its initial public offering.

NAS also may announce several acquisitions in 2000, Aust said.

Aust said another thing that separates him from his competition is that he is focusing on delivering more than DSL, offering other types of network access and helping customers design, integrate, maintain and secure their networks--all in one package. By bundling such services, Aust says he could save customers 50 percent to 70 percent on their network costs.

Aust, whose brothers James and Steve work with him at the company, said dealmaking--he expects three more big announcements by January--has left little time for karate. He usually competes in a 13-city tour sponsored by the National Karate Association, where last year he took second place in his age group. His daughters, Alexandra, 9, and Nicole, 6, who both have black belts as well, also compete. Alexandra has been No. 1 in the country in her age group for three years.

"I ended up not doing it this year because of the IPO and all that stuff, which is really regretful," Aust said. Especially, he added, since karate has always been the way in which he could be assured quality time with his children. His son, Christopher, 4, has even started taking lessons from the family instructor, local karate superstar Jeff Smith, who was a seven-time lightweight champion during the 1970s and 1980s.

Aust's wife, Longma, stopped her karate training before reaching black-belt status.

"I really hope I can get back into it," Aust said, adding that it was his karate that helped him maintain his sanity during his company's exhausting "road show" before the IPO, when he had to treat each meeting with a potential investor as if it were the first.

"When you're fighting someone, or sparring with someone, you really better focus or they're going to hit you," he said. Similarly, "on the road show, you are absolutely just physically and mentally drained, and you have to keep going."

CAPTION: Jon Aust founded fast-growing Network Access Solutions in 1995. The company, which went public in June, provides Internet-access services to businesses. In the past year, the company has grown from 35 employees to more than 400.