July 14 (Bloomberg) -- Lance Armstrong may find a record- extending eighth Tour de France win out of reach unless he can improve in the second half of the race, his fitness coach Chris Carmichael said.

Armstrong is competing in the Tour after a four-year absence in the highest-profile sports comeback since Michael Jordan returned to the National Basketball Association at age 38 in 2001. At 37, Armstrong would beat Belgian Firmin Lambot’s 1922 mark as the oldest winner by 18 months.

“Lance hasn’t got that fifth gear back,” Carmichael, who has worked with Armstrong for 20 years, said in a telephone interview. “It can still come, that fifth gear. He’s got a good shot, although Alberto (Contador) is the favorite.”

Armstrong is eight seconds behind leader Rinaldo Nocentini of Italy after 9 of 21 stages. He dropped to third after Contador, the 2007 winner, sprinted past him on the first mountain stage on July 10 to get ahead by two seconds. The event resumes today after a rest day.

Contador is 4-9 to win the Tour on Betfair.com, a London- based betting exchange, while his American teammate is 9-2. The odds on Contador mean a winning $9 bet returns $4 and the original wager.

Tests taken while Armstrong was training last month in Aspen, Colorado, found his heart rate, power output and blood lactate were “pretty doggone close” to when he quit pro cycling four years ago, Carmichael said. Armstrong has “very low amounts” of lactate, which causes muscle fatigue, Carmichael said, without giving details for privacy reasons.

Three Years Off

Even so, more than three years away from competition -- when Armstrong would typically do only a couple of hours of exercise a day -- means he can’t dominate like he used to, Carmichael said. He initially advised Armstrong against a return because “most comebacks don’t work.”

Jordan was slowed by sore knees on his return with the Washington Wizards. Armstrong may face similar physical issues.

“You’re not going to see Lance as physically dominant,” Carmichael said. “If he wins the Tour it will be because of his experience, his mental fortitude.”

Contador, who lost ground on Armstrong in stage 3 after a tactical error, surged past him with 1 mile left of the July 10 stage to the Andorran ski resort of Arcalis, finishing 21 seconds ahead of the seven-time champion.

‘Impressive Attack’

“I wouldn’t say that I could have easily followed because it was an impressive attack,” Armstrong told the France-2 television station. “I probably could have gone but I didn’t see it coming and it wouldn’t be correct for me to go across. So, I waited for the others guys,” he said, referring to Levi Leipheimer and other teammates.

Armstrong said he expects a lull in the contest to win the race over mainly flat stages the next few days until riders enter the first Alps finish to Verbier, Switzerland, on July 19. The Tour ends in Paris on July 26.

Armstrong turns 38 in September, and his age will have sapped him of some of the power of his heyday, says Greg Whyte, a professor of applied sports and exercise science at the U.K.’s Liverpool John Moores University.

“Physiologically, he’s got an incredibly tall order,” Whyte said. Since 2005 he will have lost muscle strength and endurance. The optimal level of oxygen uptake in the body during intense exercise -- called VO2 max -- falls about 1 percent a year in athletes in their mid-30s, he added.

Carmichael said he didn’t measure Armstrong’s VO2 level because it was too troublesome, requiring time spent in a laboratory.

“We’ve worked on the fact he’s a little older,” Carmichael said. “We’ve been increasing protein in shakes to make sure he’s got muscle tone.”

Special Boots

Armstrong has also been using so-called compression boots to speed blood flow after stages, helping his recovery, Carmichael said. The device has been used in pro sports for about two years, he added. It may not be enough to keep up with Contador, 11 years his junior, Whyte said.

“What happens in the Alps will be a real test of his ability,” Whyte said. “The longer the race goes on the more problematic the declines in his body become.”

To contact the reporter on this story: Alex Duff in Madrid at aduff4@bloomberg.net.

Last Updated: July 13, 2009 19:29 EDT