LOS ANGELES (AP) After four years of measuring every workout, every race with stopwatches, the elite runners competing Saturday in the U.S. Olympic Team Marathon Trials might find their fate determined by the thermometer.
With nearly 400 runners expected to step to the starting line in downtown Los Angeles, temperatures could reach 80 degrees as the field races for the first six spots - three men and three women - on the U.S. team in Rio de Janeiro.
''It's going to be a huge factor because it's going to slow down the race,'' said Bobby Curtis, the fastest American in the 2014 Chicago Marathon. ''It's going to be a little bit of a neutralizing factor. Someone like Dathan (Ritzenhein) who is a 2:07 guy can't necessarily just run away from everyone on an 82-degree day.''
Meb Keflezighi is considered a favorite in the men's division thanks to his Olympic silver medal in 2004 and his win in the Olympics Marathon Trials four years ago. He won the 2014 Boston Marathon in a personal-best 2 hours, 8 minutes, 37 seconds, and will be attempting to become the oldest U.S. Olympic marathon runner at age 40.
''The weather will be a factor,'' Keflezighi said. ''Unfortunately, we're starting at 10 o'clock (in the morning) instead of 6:55 (like the Los Angeles Marathon on Sunday). Luckily, I've run well in the heat.''
The wild card in the men's division will be Galen Rupp. A seven-time U.S. champion at 10,000 meters and a 2012 Olympic silver medalist at that distance, the 29-year-old Rupp will be making his marathon debut.
''I would never bet against Galen,'' said Luke Puskedra, the fastest U.S. marathoner in 2015.
''But if you go out of your way to beat any one person; if I go out and try and beat Meb, if I try and beat Dathan (Ritzenhein), there's always somebody else. You can't under-estimate anybody in the field.''
Ritzenheim is also a strong contender based on his fourth-place finish in the 2012 Trials, and his victory in the 2012 Chicago Marathon in 2:07:47, making him the third-fastest U.S. marathoner ever.
In the women's division, Shalane Flanagan, the Trials defending champion and second-fastest U.S. woman marathoner ever, is considered the one to beat.
''I've honestly never run in temperatures expected for tomorrow,'' the 34-year-old Flanagan said. ''I'm just going to listen to my body as much as I can. I know it's going to be uncomfortable for a large part of the race and that it is going to take its toll eventually. Just knowing that is going to help.''
Desiree Linden, who finished second in the Trials four years ago, appears to be the other woman most likely to qualify.
''You have to understand what your fitness level is, and make the necessary adjustments,'' said Linden, who was forced to pull up with an injury four years ago in London. ''The heat is going to obviously play a part. It's handling that last 10K and being able to finish the marathon, and not only just hanging out and getting in, but you have to be able to close well in the last 10K.''
According to USA Track & Field, 211 men and 246 women met the standards for the Marathon Trials. To qualify, men needed to run a marathon in 2:19, or a half-marathon in 1:05 between Aug. 1, 2013, and Jan. 17, on a USA Track & Field certified and sanctioned course. Women needed to post a 2:45 in a marathon or a 1:15 in a half-marathon.
''Once three men and three women cross that finish line, all three are winners,'' Shalane said. ''Third is just as important as first. I enjoyed winning for about seven seconds but (this race) is honestly a celebration of the men and women going to the Olympics.''