Olympic sprint champion Usain Bolt in limbo — how slow will he go?

Usain Bolt must have a bad hamstring, which would explain why the dazzling sprinter who set three world records while electrifying crowds at the Beijing Olympics lost twice to compatriot Yohan Blake at the recent Jamaican Olympic trials. It also would explain why Bolt, who previously hadn’t lost a 200-meter race other than a qualifying heat since 2007, afterward visited his longtime sports doctor in Germany for treatment and then withdrew from the final London Olympics tuneup meet last week in Monaco.

No, the problem must be that Bolt’s back is acting up again. The evidence offered by breathless British press reports: Bolt asked for a 7-foot-long, customized and orthopedically friendly mattress to be delivered to his room at the Jamaican team’s pre-Olympic training headquarters in Birmingham, England, the better to cradle his lanky, 6-foot-5 frame and ease his chronic back problems.

The real reason for Bolt’s defeats probably combines the discomfort of a balky hamstring, the woes generated by a congenitally curved spine and the emergence of training partner Blake as a new and younger rival to his supremacy in perfect time for a memorable showdown at the London Summer Games.

But don’t write Bolt off just yet.

“Every time he has been severely challenged and it looks like he maybe has a chink in the armor he has bounced back pretty strong,” said Ato Boldon, a four-time Olympic sprint medalist and four-time world championship medalist for Trinidad and Tobago who will analyze track events during NBC’s Olympic coverage.

“I am not one of those who think he is automatically going to lose in London. But for the first time he is not the favorite in the 100.”

With Bolt and his teammates sequestered at the Jamaicans’ practice facility, no reliable reports about Bolt’s fitness have surfaced. That has left fans of the sport to wonder if the charismatic sprinter whose playful personality is reflected in his trademark “Lightning Bolt” post-victory pose — right arm drawn back at shoulder height, left arm extended with his left index finger pointing toward the heavens — has lost some of his thunder to Blake.

Bolt might provide some illumination Thursday, when the Jamaican team is scheduled to participate in a pre-Olympic news conference in London. Bolt’s agent, Ricky Simms, told reporters two weeks ago the hamstring tightness Bolt had felt during the Jamaican meet had vanished and that Bolt was “back to normal . . . good to go.”

For the 25-year-old Bolt, “good to go” usually means stunning performances like his world-record 9.69-second clocking in the 100 at the Beijing Olympics and a relaxed approach. His pre-race meal was chicken nuggets, a nutritionist’s nightmare but, at least for him, the dinner of champions. He lowered his record to 9.58 a year later in Berlin at the world championships and followed that four days later by breaking Michael Johnson’s revered world record in the 200 with a blazing time of 19.19 seconds, all the while winning fans with his down-to-earth demeanor.

Only his high-speed driving antics, which have led to several car accidents, stand between him and utter adoration within his country and among fans around the world. A sport plagued by years of doping scandals and administrative bumbling couldn’t hope for a more magnetic athlete to help repair its image while competing in the signature event for the title of world’s fastest man.

“He’s the best thing to happen to track and field in my lifetime,” Boldon said. “I think he has that ability to take the sport into a place where, coming back off the Marion Jones stuff and the Tim Montgomery stuff and the BALCO stuff, he really has been a breath of fresh air for the sport.

“His personality is just a complement to his ability. His performances get your attention. His personality is what has kept the attention of the entire planet for the last four years.”

But Bolt’s results at the Jamaican trials gained attention for the wrong reasons.

Blake, who won the 100-meter world title last year after Bolt was charged with a false start and disqualified, beat a slow-starting Bolt with a personal-best 9.75 seconds in the 100 final. Two days later Blake, 22 and a contrast to Bolt at a stocky and powerful 5 feet 11 and 175 pounds, capitalized on another bad start by his rival to win the 200 in 19.80. Bolt was second at 19.83.

At a meet last week in Lucerne, Switzerland, Blake overcame his own slow start to win the 100 in 9.85. Only Blake, Bolt and American sprinter Justin Gatlin have run faster this year. “I didn’t come here to run a quick time, but it’s still a fast time. Not many guys run 9.85,” Blake told reporters.

Bolt has three faster times this season, but his losses to Blake at the Jamaican trials stand out as the Olympics approach. Boldon said Bolt’s poor starts in the trials shouldn’t be seen as the start of a bad trend.

“Bolt knows very well he cannot go to the Olympics and start like that. If he starts like that in the Olympic final, he loses. He may not even get second,” Boldon said. “But the thing is, in his championships history, he does not start bad at championships, the false start last year notwithstanding.

“I don’t know how he does it, but he always seems to figure it out by then. He can be starting poorly the entire year, like he was in 2011, and somehow he finds a way to figure it out for the championships.”

Boldon said he considers Tyson Gay, the American-record holder in the 100, “extremely dangerous . . . sort of the overlooked guy,” and capable of beating Bolt at that distance.

“I think there’s only one person who can beat him in the 200 and that’s Blake,” Boldon said. “In the 100 there’s two or three.”

During a visit to Los Angeles last September Bolt said a world-record performance would be required to win gold in London.

“My ultimate dream is to go to the Olympics and wow people,” he said. “I want to be a legend.”

He can be, if Lightning strikes again.

helene.elliott@latimes.com

twitter.com/helenenothelen