Heat coach Pat Riley put action Tuesday behind his preseason promise to change the attitude of a team coming off a lackluster season, the Miami Herald is reporting.

He gave the Heat a wake-up call on the opening day of training camp. Literally. Riley surprised his team Monday when he told players to arrive at AmericanAirlines Arena at midnight Tuesday for practice.

The first of Tuesday's two scheduled practice sessions was originally to begin with a 9 a.m. meeting. Seventeen of the 20 players on the camp roster adjusted. Three didn't.

Forward Antoine Walker, center Earl Barron and guard Smush Parker were held out of practice for failing to meet Riley's conditioning standards.

Riley said the three players spent Tuesday's second session riding stationary bikes at the arena to meet the team's body fat standards. Parker and Walker also were limited by injuries, Riley said.

''I'm doing what I have to do,'' said Riley, who would not disclose which standards the players have yet to meet. ``That's just the way it is. They've got to meet their goals. They're all very close [but] I'm playing with guys who are ready.''