Mesa - Michael Phelps has dramatically increased his workload for the next stage of his comeback to competitive swimming, offering more possible clues to his intentions for the 2016 Rio Olympics.
The 28-year-old American has entered four events for the June 19-22 Grand Prix meet in Santa Clara, double what he swam at two previous meets since coming out of retirement.
He does not have any events on the first day of competition in Santa Clara but is entered for each of the other three days, providing him with an early test of his speed and stamina.
On Friday he will contest the 100 metres freestyle, an event he has never swum at the Olympics, but one that he needs to set a qualifying time in so he can make the U.S. 4x100m freestyle relay team.
Phelps is also entered in Friday's 100m butterfly, one of his favourites events. He won gold in the event at each of the last three Olympics and has already competed in it at his two previous meets.
On Saturday, Phelps is entered for the 200m freestyle, though it remains to be seen whether he is planning to stick with that event or just use it to qualify for the 4x200m relay, which the United States have won at the last three Olympics.
Although Phelps won the individual 200m freestyle final at Beijing, where he captured an unprecedented eight golds, he skipped the event for the 2012 London Olympics and would seem less likely to add it for Rio after saying he wanted to reduce his programme.
He entered the 200m freestyle at a Grand Prix meet in Charlotte last month but did not compete in the final after swimming fast enough in the heats to qualify this year's U.S. national championships in California.
For Sunday, Phelps has entered the 200m individual medley, another event he won at the past three Olympics.
He has not swum the multi-discipline race since London but his inclusion in the heats could be a pointer to what he may enter in Rio although Phelps and his coach have refused to discuss their plans and are keeping everyone guessing.