You have to get up pretty early in the morning to beat Dan Rincon or Julie Shea, the leaders of the pack in yesterday's 10-mile Cherry Blossom Classic.

Early birds both, they were the No. 1 man and woman among the 1,608 serious distance runners and reasonable facsimilies thereof who crossed the finish line in this popular rite of spring, which has been run annually since 1973 along a route lined with budding trees, lush lawns and fragrant gardens in East Potomac Park and environs.

Rincon, 24, arises every day at 5 a.m. to run five miles before reporting to work as an office assistant at the Student Union of his alma mater, the University of Maryland. He covered the picturesque course in 49 minutes 44 seconds on a windy but pleasant morning for his first victory in a road race of this caliber.

Shea, 17, a high school senior from Raleigh, N.C., got up at 1 a.m. to make the drive to Washington with her father, younger sister and brother, all of whom ran well. Julie was the top woman in the Cherry Blossom for the third consecutive year and broke her own U.S. record for 10 miles with a clocking of 56:08.

Her sister Mary, 16, who also represents the Raleigh Junior Striders, finished fourth among the women in 60:31. Mike Shea, 48, an assistant track coach at North Carolina State from 1957-67, topped the men's 45 to 49 age group. Brother Mark, 13, did not place in the boys 13-to-19 bracket, but was pleased with his and the family's performance.

Rincon, an All-America in cross country and winner of the Atlantic Coast Conference six-mile championship in 1975, his senior year at Maryland , outdueled defending champ Carl Hatfield. The 29-year-old, two-time winner from Philippi, W. Va., finished second in 50:29.

Rincon had won a couple of small road races, but his best finish in an event comparable to this race was third in the AAU 30-kilometer championships at Albany, N.Y., two weeks ago. This was his first Cherry Blossom.

Rincon was 35 seconds off the race record of 49:09 set by Hatfield last year, primarily because of the stiff breeze and an exhausting early pace.

"We went out too fast. Dan and I did the first mile in 4:30," said Hatfield, who wound up battling stomach cramps while Rincon made his break 4 1/2 miles into the race. "If we had run the rirst mile more sensibly, our times might have been better."

If he had run the first mile more sensibly, Hatfield thought, he might have won the race. But Rincon caught him with his guts rebelling and his emotional and physical battery discharging.

"I came in planning to make my move at about five miles," said Rincon, a Vermont native who represents the Delaware Sports Club. "But at 4 1/2, I felt confident I could make my break and carry it the rest of the way. I gambled and it worked. When Carl didn't try to go with me, I was sure I could win it."

"He really spurted on me and I couldn't respond," said Hatfield, of the West Virginia Track Club. "In the space of 200 yards he got 40 yards in front of me and I never could catch him.

"I think the first mile affected me more than him. If I could have stayed with him when he made his break, he might have gotten discourage. He must have been hurting as much as I was. But I couldn't put it to him."

Rincon and Hatfield set the ambitious early pace, talking to each other as they started out near the golf clubhouse in East Potomac Park.

The chalked arrows on the road mapped a course that wound around Hains Point and up the Potomac River side to the Tidal Basin. The runners circled Fanne Foxe's old swimming hole, made a short out-and-back sally along the river toward the Lincoln Memorial, then retraced their strides along Ohio Drive back to Hains Point and up the Washington Channel side of the park to the starting-finish line.

Rincon felt "tight and heavy" for the second mile as he fought the wind and aftereffects of the fast start. When the pack caught up with him and Hatfield shortly thereafter, he "settled in with it and tried to get myself relaxed and back together," as Bruce Robinson of Silver Spring (fourth in 50:53) took the lead.

Rincon caught up with Hatfield and Robinson at 3 1/2 miles, ran with them for a mile, then took the lead for good.

Julia Shea looked as if she meant business before the starter's gun sounded. Her face was a snarl of concentration while many in the field of 1,700 for the 10-mile event (700 others entered a two-mile "fun run") were still smiling and kibbitzing with well-wishers in the crowd.

The tall, slender Shea, who is bound for N.C. State on a track scholarship next fall, bounced up and down, ran in place, then crouched for the start as if she were a sprinter, the first inch as important to her as the last.

No other woman challenged her. Second-place finished Aileen O'Connor of College Park and the Catholic Youth Organization (the winning woman's team) finished in 58:28, 2 minutes 20 seconds behind Shea. Carol Fridley of Elizabethtown, Pa., was third in 59:20.

Shea, who has been running and winning for eight years, ate her customary prematch breakfast of French toast. "It's a habit. I can't run without it now.My dad makes it the way I love it - nice and eggy," she said before leaving for a family outing at the National Zoo.