By Mike Collett-White

LONDON (Reuters) - British hope Jessica Ennis, the poster girl of the London Olympics, lit up a packed stadium on Friday where the track and field events got under way but the hosts' cycling team were under scrutiny after a "planned" crash.

Britain's men took cycling track team sprint gold on Thursday but German-born rider Philip Hindes fell over on his bike in the qualifiers and later revealed the reason.

"I did it on purpose to get a restart... it was all planned really," he told reporters, prompting shock among British media and leading to calls for a change in the rules.

British cycling officials, who hope for more glory on Friday in the men's team pursuit and women's keirin, later said his comments were lost in translation.

The home nation is storming up the medals table and a further gold could come in the heptathlon with Ennis setting a world best time in the 100 meters hurdles as the focus of the Games shifted from swimming to athletics

World champion Vivian Cheruiyot of Kenya begins her bid for a distance double in a much-anticipated 10,000 final where Ethiopian Olympic champion Tirunesh Dibaba, who has the fastest time of the year, is expected to be her main rival.

Cheruiyot also has her eye on the 5,000 next week as she attempts to replicate her double gold from last year's world championships.

Elsewhere in track and field, a trio of Americans will seek to capture the men's shot put gold for United States for the first time since 1996.

Reese Hoffa, Ryan Whiting and Christian Cantwell, silver medalist in Beijing four years ago, set out to dethrone Olympic champion Tomasz Majewski of Poland with Germany's world title holder David Storl also likely to be in strong contention.

With the opening of the athletics, the jewel in the Olympic crown, excitement has begun to build towards Jamaican Usain Bolt's defense of his 100 title on Sunday and his 200 crown four days later.

PHELPS PHENOMENON

In swimming, Michael Phelps will race his last individual Games event in the final of the 100 butterfly.

Two days after breaking the all-time record for the most Olympic medals with 19, Phelps added a 20th - and his 16th gold - by winning the 200 individual medley.

In their final duel before Phelps is due to retire, he pushed fellow American and world champion Ryan Lochte into second place and became the first male swimmer to win the same individual event three times at successive Games.

Missy Franklin, 17, chases her third gold medal in the 200 backstroke while Rebecca Adlington carries British hopes in the 800 freestyle, bidding to repeat her victory in Beijing.

United States also celebrated victories on Thursday in the women's rowing eight and for 16-year-old Gabby Douglas in the all-around gymnastics where she edged out Russian Victoria Komova who was too upset to wear her silver medal.

"People keep saying I was the first black American to win the gold medal and I'm so honored," Douglas, nicknamed the Flying Squirrel, told reporters after claiming the biggest prize in women's gymnastics.

She helped the United States catch up with the Chinese in the overall medal standings, with both countries on 18 golds on day seven of full competition.

Black belt Vladimir Putin cheered Russia's Tagir Khaibulaev to the country's third judo gold on Thursday.

In a scandal over match-throwing in the badminton tournament, disqualified Chinese Yu Yang announced she was quitting the sport.

"This is my last competition. Goodbye Badminton World Federation, goodbye my beloved badminton," Yu wrote on her microblog.

She was one of eight women, two each from China and Indonesia and four from South Korea, kicked out of the Games for playing to lose group matches in order to secure easier knockout opposition.

The badminton debacle and the cycling issue have been among the few sour notes of a Games distinguished by enthusiastic crowds and Phelps's remarkable feats.

In the rowing, Nathan Cohen and Joseph Sullivan won the double sculls for New Zealand on Dorney Lake, west of London.

Fellow Kiwis Eric Murray and Hamish Bond, unbeaten since 2009 and victors in the last three world championships, will seek to emulate them on Friday in the coxless pairs.

(Editing by Tony Jimenez/Mark Meadows)