Jane Newell of Reston took the lead at the start of the First American Bank Women's Biathlon yesterday in Arlington's Barcroft Park and maintained it throughout the 6.2-mile run and 15-mile bicycle course, finishing more than seven minutes ahead of the runner-up.

Christie Hutchinson of Chesapeake City, Md., finished sixth in the running event but rallied in the bike race to take second overall. Sandy Ford of Columbia, Md., was third.

Newell's outstanding performance (she finished the run in 37:57 and the event in 1:24.04) was even more surprising considering the high temperature and humidity that sent one competitor to the hospital suffering from heat exhaustion and affected many others.

"The heat was tough," said Hutchinson, who said a wrong turn in the run cost her a couple of minutes. "It slowed everybody down."

The victory came easily to Newell, who had a 4 1/2-minute lead at the transition from running to biking.

The victory was Newell's third in as many events in the Capital Area Biathlon Series since March, although she is still a relative newcomer to biathlons and triathlons.

After the birth of her second child two years ago, Newell trained in her basement for the first time to get into shape. "It's amazing how much potential you have that you don't know about if you are willing to push real hard," said Newell.

A fourth-place finisher in the 1985 national triathlon championships in her 25- to 29-year-old age group, Newell, 27, has been approached to join several well-known triathlon teams that compete on the national and international level. But Newell said she has no desire to get that serious about the sport.

"This fits into my life style but it's not the primary focus," said Newell. "I'd lose a lot of the fun if I went any further."

Marjorie Lane, 53 and the oldest competitor in the event, placed first in the 50-and-older age group over seven others. Finishing in 2:20, Lane said she just missed her goal. "I was hoping for just under two hours," she said.

Although she has competed in marathons and other running/biking events, this was Lane's first biathlon. "I get a kick out of passing someone who looks like they are considerably younger than me," said Lane. "It really feels good."

Of the 110 women who started the event his morning, all but 10 finished. Two were taken to the hospital during the event.

Ellen Molotsky of Washington was taken to D.C. Orthopedic Hospital and treated for heat exhaustion she suffered during the bicycle race. Another competitor was treated for an allergic reaction.