The brutal heat and humidity that has gripped the Washington area for the past week continued unabated yesterday, with only afternoon showers as respite from temperatures that topped 90 degrees for the sixth straight day.

The heat took its toll. Area hospitals reported numerous cases of heat exhaustion. About 100 participants in two distance races were treated for heat-related problems. Two were hospitalized.

The official high for the day was 92 degrees, with the humidity reaching a stultifying 91 percent.

At the second annual Reston Triathlon, two participants and a spectator were treated after being overcome by the heat, and a third participant suffered a broken collarbone in a bicycle accident.

All but the spectator were treated and released from the Access Emergency Center in Reston. The spectator, Richard Parsons, 55, of Reston, was treated for chest pains and then transferred to Fairfax Hospital, where he was listed in serious but stable condition.

Director Norm Happ said the triathlon -- a one-mile swim, 25-mile bicycle race and 10-kilometer run (6.2 miles) -- drew 340 participants. It began at 8 a.m., and most racers finished by 11 a.m., when the temperature was 89 degrees and the humidity 58 percent.

About 40 people were treated at the South Lakes High School gymnasium for cramps and dehydration, Fairfax County fire and rescue officials said.

Happ said organizers decided not to cancel or shorten the race after consulting with a team of physicians. "We warned the racers of the symptoms of heat stroke, and we put out extra water stations and had extra police watching them the racers ," he said.

In addition, eight massage therapists from the Potomac Myotherapy Institute in Washington volunteered to give participants massages after the race. About 65 people took the company up on its offer, said therapist Mack Wood.

Betty Blank, 32, of Falls Church, was one of the participants who was treated. "I've run 10 triathlons and 15 marathons before," she said, "and I've never felt this bad. It was suicidal to race in this heat wave."

Karen Lovelace, 45, of McLean, who was treated for cramps after the race, said the swimming and bicycling portions of the race were fine, but "the run was the most awful thing I've ever been through."

Bob Dydo, 41, of Vienna, agreed. "By the time you get to the run, you've done two events, and you have to hold back a little or it will kill you," he said.

At the United Way Kickoff 10-Kilometer race through West and East Potomac parks, about 60 of 800 runners were treated for heat-related problems.

Michael Pufnock, 39, of Burke, was listed in serious condition at George Washington University Hospital last night after collapsing about five miles into the race.

When emergency medical technicians reached him, his body temperature was 108 degrees, he had stopped sweating and his pupils were dilated, said Joel Kahn, chief of the American Red Cross Aid Corps.