The Latest from the world championships (all times local):
Jamaican team doctor Kevin Jones said Usain Bolt had a cramp in his left hamstring.
Bolt grimaced in pain as he was running down the finishing straight before stumbling and falling to the track.
"A lot of the pain is from disappointment from losing the race," Jones said. "The last three weeks have been hard for him, you know. We hope for the best for him."
Usain Bolt failed to make it to the finishing line in his last race.
The Jamaican great crumpled on the track with a left leg injury as he was chasing gold in the 4x100-meter relay at the world championships.
Instead, Britain upset the United States to take gold in 37.47 seconds. The Americans were .05 seconds behind. Japan took bronze in 38.04.
Tori Bowie became the first double gold medalist at the world championships, anchoring the U.S. team to the 4x100-meter relay title ahead of Britain and Jamaica.
At the same time, Allyson Felix, running the second leg on the winning team, earned a record 15th medal at the world championships in a career going back to 2005.
Bowie, who won the 100 meters this week, ran a strong anchor leg, leaving behind the opposition to finish in 41.82 seconds.
Britain took silver in 42.12 and two-time defending champion Jamaica earned bronze in 42.19.
Johannes Vetter won the javelin title at the world championships with an opening throw of 89.89 meters.
The German beat Jakub Vadlejch of the Czech Republic by 16 centimeters. Another Czech, Petr Frydrych, took bronze with a last throw of 88.32 meters.
Olympic champion Thomas Roehler of Germany finished fourth.
Kevin Mayer is the new "world's greatest athlete."
The Frenchman produced a dominant performance over two days and 10 events in the decathlon, ending with a celebratory 1,500 meters at the world championships.
With two-time Olympic and world champion Ashton Eaton now retired, the event was wide open. Mayer won with 8,768 points. Rico Freimuth took silver with 8,564 points, while German teammate Kai Kazmirek was third with 8,488.
Mayer is the first Frenchman to win the title. He had only one scare during the two days of competition — when he scaled his opening mark of 5.10 meters in the pole vault on his third and last attempt.
Mariya Lasitskene of Russia won the high jump competition at the world championships by clearing 2.03 meters.
Yulia Levchenko of Ukraine jumped 2.01 meters for silver and Kamila Licwinko of Poland took bronze with a jump of 1.99.
Lasitskene, the defending champion, was unable to compete at last year's Olympics because of the suspension of Russia. She competed in London as a neutral athlete.
Olympic champion Ruth Beitia, who is 38, tumbled out early in the high jump final.
Muktar Edris of Ethiopia broke the hold of Mo Farah on long-distance running, outkicking the Briton over the final 200 meters to win the 5,000 meters at the world championships.
In a tactical race, Farah could not respond to a challenge for the first time in six years, turning his farewell race on the track at a major championship into a disappointment.
Edris won in 13 minutes, 33.79 seconds, .43 seconds ahead of Farah in second. Farah was going for his fifth straight global long-distance double.
Paul Chelimo of the United States took bronze.
Olympic champion Ruth Beitia tumbled out early in the high jump final at the world championships.
The 38-year-old Spaniard had three failures at 1.92 meters. With a mark of 1.88, she was last in the 12-women competition.
The 11 others all scaled 1.92.
Sally Pearson is back and getting another gold medal at the Olympic Stadium in London.
Five years after winning the 100-meter hurdles at the London Games, Pearson won the world championship title in 12.59 seconds after missing much of the past two seasons because of injury.
American veteran Dawn Harper Nelson was second, .04 seconds behind, and Pamela Dutiewicz of Germany took bronze in 12.72.
World-record holder Kendra Harrison finished fourth.
Hard to miss Inika McPherson. She's the one with the mohawk and what looks like the bottom half of a Batman mask painted on her face.
The heavily tattooed, 5-foot-4 American high jumper is in the final, and gathering as much attention for her look as her jumps.
Kevin Mayer took a commanding lead over Rico Freimuth at the world championships heading into the final event of the decathlon — the 1,500 meters.
The Frenchman threw 66.10 meters in the javelin and has 8,067 points after nine events, 173 more than Freimuth. Another German, Kai Kazmirek, is in bronze-medal position with 7,796 points.
Defending champion Ashton Eaton retired this year after winning the last two Olympic and world titles.
Kevin Mayer of France extended his lead in the decathlon after the pole vault, clearing 5.10 meters in the eighth of 10 events at the world championships.
Mayer has 7,237 points, followed by Rico Freimuth of Germany with 7,121. Freimuth cleared 4.80 in the pole vault.
Another Germany, Kai Kazmirek, also jumped 5.10 and moved into third place with 7,021 points.
Only the javelin and the 1,500 meters remain in the competition.
Rico Freimuth closed in on decathlon leader Kevin Mayer by producing the longest throw in the discus at the world championships.
Mayer had a throw of 47.14 meters and leads with 6,296 points after seven events, but Freimuth set a mark of 51.17 to close within 24 points of the leader in the 10-event competition.
Oleksiy Kasyanov of Ukraine was in third position with 6,095 points.
After crashing in the hurdles and being disqualified from the event, two-time world champion Trey Hardee fouled three times in the discus and is totally out of contention.
The U.S. 4x400-meter relay team set the fastest time of the year to qualify for Sunday's final at the world championships, beating Trinidad and Tobago and Belgium.
Running several alternates on their team, the United States finished in 2 minutes, 59.23 seconds, .12 seconds ahead of Trinidad and Tobago.
In the opening heat, Spain beat Poland and Cuba for the three automatic qualifying spots but Jamaica was out, finishing fourth.
Usain Bolt and Justin Gatlin will meet in a final duel on the track after helping their teams qualify for the final of the 4x100-meter relay at the world championships.
The United States, with Gatlin running the second leg, won the first heat in a world leading time of 37.70 seconds. The Americans beat Britain and Japan, who also qualified.
Then came Bolt, and the Jamaicans needed him. Trailing when he got the baton on the anchor leg, Bolt powered away and quickly swept past his rivals and had time to look to his right before crossing in 37.95 seconds.
France and China also qualified.
Allyson Felix stayed in line to become the athlete with the most medals in world championships history when she helped the American 4x100-meter relay team qualify for the final later Saturday.
Running the second leg, Felix and her teammates crossed first in a season's leading time of 41.84 seconds, beating Britain and Switzerland. They also advanced to the final.
In the second heat, Germany beat two-time defending champion Jamaica to qualify along with Brazil.
The Netherlands, with 200-meter champion Dafne Schippers running the second leg, qualified on time.
Felix has won 14 medals at the world championships and can move up to 16 if she runs the 4x400 relay and the United States wins medals in both events.
Trey Hardee of the United States hit the third hurdle and clattered into the next one during the 110-meter hurdles to end his medal chances in the decathlon at the world championships.
The two-time world champion was later disqualified for deliberately knocking down a hurdle.
In the first of five events on the final day of the two-day competition, Kevin Mayer of France set a third personal record to easily stay atop the standings with 5,485 points. Rico Freimuth of Germany was in second place with 5,377 points, while Damian Warner of Canada had the fastest time in the hurdles of 13.63 seconds to move into third.
Saturday marks the end of the Usain Bolt's career.
The Jamaican great is looking for one more gold medal in the 4x100-meter relay at the world championships.
The relay heats are set for early Saturday. If everything goes according to plan and no batons are dropped, it will also mark the final duel between Bolt and American rival Justin Gatlin, who beat the Jamaican in the 100 final last weekend.
Also, British runner Mo Farah will compete in his last race on the track at a major championship when he goes for a fourth straight world title in the 5,000. He won a third 10,000-meter gold on the first day of the championships.
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