When Grete Waitz recalls running her first marathon in New York City in 1978, she credits her husband and coach, Jack, for encouraging her to attempt the distance.

Today, the Norwegian couple will switch roles. Jack Waitz will be starting his fifth marathon while his wife, who won her seventh New York Marathon last week, plays spectator/coach. Jack Waitz will join almost 11,000 runners for the 10th Marine Corps Marathon, beginning at 9 a.m. at the Iwo Jima memorial in Arlington. His wife is in town to promote her new running videotape.

"I've been looking for a marathon for a long time, because the marathons I would like to do always interfere with some of (Grete's) racing," said Jack Waitz, 38, whose best time for the 26-mile 385-yard distance is 2 hours 39 minutes. "I have to be careful. My longest runs these days are normally less than an hour. I'm just worried about my lack of long runs. That's my problem."

But he said he never has had a problem with being known as Grete Waitz's husband.

"It's no problem at all (when Grete gets all the credit)," said Jack Waitz, who has been promoting Adidas for the past four years while his wife has competed full time as a world-class distance runner. "I think that she deserves everything. Through her running, I've accomplished a lot. Sometimes I think I'm really more happy about her performances than Grete is. Because of Grete, I have been able to travel a lot and see a lot."

Although Jack Waitz does train with his wife on her first workout of the day at 5:15 a.m., the only clashes they have in their coach/athlete relationship is "when he doesn't let me do the training that I want to do," Grete said, laughing.

As for his running career, now in its 30th year, "It's all right for my ambitions: to keep in shape. I'm not serious."