Ken Mueller was not a hard man to pick out of the 143 participants in yesterday's National Master AAU 10-kilometer cross-country championship in Arlington, even though the Bellingham, Mass., physical education teacher stands just 5-foot-6 and weighs 130 pounds.

To the crowd, he was identifiable by his gloves and bright orange wool ski cap. To his competitors, he wa the one way out front for the final three kilometers.

Mueller, who says he run better as the races get longer, covered the 6.2-mile Bluemont Park course in 33:57.8, facing a stiff wind and temperatures in the low 40s. Ralph Bowles of Pleasant Hill, Calif., was second in 34:11.

Running for the Boston Athletic Association, Mueller stayed close with the leaders as the pack headed into the wind through the first four kilometers. Then he made his move.

"I laid back and drafted behind a couple guys on the way out," said Mueller, who has averaged 100 miles a week in training for the past 60 weeks. "Once we hit the corner, I put the pressure on."

Bowles, whose specialty is hills, was within 20 yards of Mueller before a steep incline at the seven-kilometer mark. "He (Mueller) gets to the top and I can't see him, and he takes off," recounted Bowles. "I thought he was about 15 yards ahead, but when I got to the top he was about 40. I closed a little down the stretch but I wasn't going to catch him."

Mueller figured the wind heldup Bowles. "Apparently it affected him more than me," said the 41-year-old Mueller, who last week won the New England Masters cross-country title. "When I looked back he was twice as far as before."

The Boston AA won the men's 40-49 team title behind Mueller, a fourth-place finish by John Butterfield (34:26) and a 10th-place effort by Rusty Lamade (35:06).

Bowles and third-place finisher Kent Guthrie (34:14) led the West Valley Joggers and Striders Club of Pleasant Hill to second in the team standings.

The host Potomac Valley Seniors Track CLub's 'A' team was third behind George Vernosky of Bethesda, who finished seventh individually (34:45) and won the men's 45-49 division.

Defending champion John Brennand of Santa Barbara, Calif., who missed 12 weeks of activity this summer after being hit by a car during a jog in Italy, placed fifth in 34:33. It was the fifth race this fall for Brennand, who suffered a tear in a leg tendon in the accident.

In the women's division. Trudy Rapp of Alexandria, in only her third competitive race, surprised the field of 16, including several California runners, and won by more than a minute in 39:53.

"I kept wondering who was behind me. I heard people breathing and hoped it wasn't one of those yellow San Diego T-shirts," said the 40-year-old mother of five. "I expected them to go whipping past me any minute."

Nicki Hobson of Del Mar, Calif., runner-up in last year's women's division, was second again, finishing in 40:58. "I didn't realize she (Rapp) was ahead of me for the first four kilometers," said HObson, who led the San Diego Track Club to the women's team title. "Then someone told me where she was. I started looking and finally saw her, but I couldn't get her.

"Bridesmaid again," sighed Hobson.