TOKYO — The United States continues to struggle in skateboarding, a sport that it invented and pushed into the Olympics.

Only one American, Cory Juneau, squeaked into the final of the men’s park competition, claiming the eighth and final spot on Thursday morning. But the world’s No. 1-ranked park skater, Heimana Reynolds of the United States, and his teammate Zion Wright each fell short of qualifying.

The men’s park competition is the fourth of four skateboarding events as the sport debuts in the Summer Games. Through the first three, the United States had one medal, a bronze earned by Jagger Eaton in men’s street.

Men’s park, an event filled with high-flying spins, technical board flips and long grinds on the lip of the deep and contoured bowl, looked to be the salvation, deep in American talent.

Under searing sunshine at Ariake Urban Sports Park, Wright and Reynolds finished first and second in the first heat. They had reason to hope that their scores would finish in the top eight among 20 competitors.

But scores rose like the morning temperature, and their rankings ticked down the leaderboard. First Reynolds dropped out of contention, then Wright, as Juneau skated in the final heat and took over the eighth spot.

Soon Juneau, too, was bumped out of position. He needed a big score in his third and final attempt, and got it, a 73.0 that nudged out the 72.24 by Danny Leon of Spain.

Reynolds finished 13th, Wright 11th, and they were not the only big names to miss the final. Among others was Sweden’s Oskar Rozenberg, considered a strong medal favorite, who struggled to stay upright and finished in 17th place.

Three Brazilian skaters reached the final, set for later today, by finishing among the top four qualifiers: Luiz Francisco, Pedro Quintas and Pedro Barros.

Park is contested in a deep and unsymmetrical bowl of steep drops and contours. Athletes were given three runs, ending after either 45 seconds or a fall. The best score counted. For the finals, scores will be reset back to zero.

Skateboarding made its debut at these Olympics, and skaters from Japan have dominated so far, winning gold in the first three events — men’s and women’s street and women’s park. That should boost the sport’s popularity in Japan, where skateboarding’s long history has unfolded mostly in the shadows.

The other theme for skateboarding at these Summer Games had been the ages of many top competitors. Skateboarding put no minimum age requirement on the Olympics, so five of the six youngest athletes at the Olympics were skateboarders, all of them women.

At the women’s street contest last week, the medal stand had two 13-year-olds and a 16-year-old. At women’s park on Wednesday, all the medalists were teenagers, including 12-year-old Kokona Hiraki, who won silver, and 13-year-old Sky Brown, who won bronze.

The men’s events have skewed older, and park looked like a possible outlier with an international flavor among the favorites.

The qualifying rounds even included 46-year-old Rune Glifberg of Denmark, who won an X Games medal in 1995, before most Olympic skateboarders were born. Another 46-year-old, Dallas Oberholzer of South Africa, was also in the field, sporting a smile and graying stubble.

Each rode as a sort of connective ambassador to skateboarding’s past, and both finished last in their heats and did not make the final.