PORTLAND — In the offseason, Zach Randolph stepped up his conditioning program and even dropped some weight.

Randolph’s renewed dedication was apparent Wednesday night, when he had 36 points and 10 rebounds to lead the Portland Trail Blazers to a 101-90 victory over the Los Angeles Lakers on Wednesday night.

“Randolph had a monster game,’’ Kobe Bryant said. “He commanded the paint area, drew fouls and got easy opportunities.’’

The Blazers (3-2), who led by as many as 15 points, have won five straight against the Lakers at the Rose Garden arena.

Randolph, who has averaged 28 points and 10.5 rebounds over Portland’s first five games, had a two-handed dunk to put the Blazers ahead 78-69 early in the fourth quarter.

Bryant scored 32 points for the Lakers (4-2), and made it close with a layup and a free throw that narrowed it to 93-86 with 1:41 left. But Stephen Graham answered with a 3-pointer for the Blazers to seal it.

Randolph has four double-doubles in five games this season.

“I’m feeling good,’’ he said. “I’m just trying to play hard. I’m feeling pretty good out there. I could be in better shape, but it’s getting there.’’

The Blazers led by as many as eight points in the first half, but Luke Walton’s layup and 3-pointer put the Lakers up 40-35. The Blazers closed the half with an 11-4 run to lead 55-49.

Ime Udoka, who made Portland’s roster as a training camp invitee, hit a 3-pointer to put the Blazers ahead 66-53 midway through the third period.

The Blazers were without Brandon Roy, the sixth overall pick in the June draft, who was out with a heel injury that limited him to 14 minutes in a 102-89 loss to the Clippers on Monday.

He was held out of Wednesday night’s game as a precaution, but could be back on Friday when the Blazers host New Orleans. He is averaging 18.3 points this season.

Bryant, who missed the Lakers’ first two games of the season as he recovered from last summer’s knee surgery, averaged 38.3 points against the Blazers last season. He has scored at least 30 points in eight straight games at the Rose Garden.

Randolph averaged 18.5 points and 11 rebounds in his two home games against the Lakers last season.