The biggest gymnastics meet of the year -- the world gymnastics championships -- starts Friday in Tokyo. The Americans could win big, the traditional powerhouses will challenge them, and there are all sorts of other storylines that may play out in this pre-Olympic year. Here are five you'll want to watch:
1. Wieber's worlds
American 16-year-old Jordyn Wieber is the one to beat in Tokyo. With injuries to U.S. teammate Rebecca Bross (see sidebar), defending world champion Aliya Mustafina and 2010 Youth Olympic champion Viktoria Komova, Wieber is the hands-down all-around favorite. She is also a potential medalist on the bars, beam and floor as well. Wieber does some of the toughest tricks in the book: Don't miss her double-twisting double-back on floor and her standing back flip with a full twist on beam.
2. The American gamble
When the U.S. team was announced, many experts and fans were surprised: Team coordinator Martha Karolyi chose several athletes with high-scoring potential but little experience. In fact, only two of the seven members have competed at a world championships. And the squad is full of specialists -- which can pay off big in finals, when only three scores are used in each event, but can get risky if someone gets hurt. Unfortunately, that's exactly what has happened. Bars superstar Anna Li strained her abdominal muscle in training and was named an alternate instead of a competitor on Tuesday's final roster. The U.S. doesn't have a fill-in bar worker of the same caliber as Li, so it will be counting a relatively low score in that event. Then Alicia Sacramone, the reigning world vault champion, was taken out of the lineup because of a torn Achilles' tendon suffered Thursday. The team will miss her vault and beam scores. If the newcomers can shake off big-meet nerves, the team can still win, but there's absolutely no room for error, as China, Russia and Romania are all in the mix for gold as well. More on the competition format and scoring.
Twenty years ago, Oksana Chusovitina was a 16-year-old rookie competing for the Soviet Union at the worlds in Indianapolis. She took home three medals: two golds and one silver. Now she's 36, competes for Germany and somehow is still at the top of the sport. She's won eight world medals on vault and earned the vault silver at the 2008 Olympics. This is in the realm of superhuman; most female gymnasts are considered veterans after a couple of world medals. This may be Chusovitina's last worlds -- but then again, we've been saying that for about 10 years.
4. Chinese champions?
China showed up to training in Tokyo with shirts that read "China, 2012 Champion." Bold? Definitely. But not out of the question. Though China was strongly suspected of using underage gymnasts to win in 2008, most agree the gymnasts, whatever their age, were fantastic. The team could win again in London, and a Chinese victory this year at worlds could happen, too. He Kexin and Jiang Yuyuan, two members of the 2008 gold-medal team, (and two who were speculated to be younger than 16 in Beijing) are still on the squad -- and they lead a group of supremely talented gymnasts. National champ Tan Sixin is the team's best all-arounder, and won golds on beam and floor at the Youth Olympics last year. Veteran He is still queen of the bars -- she won the 2008 Olympic title and 2009 world title in that event and comes into this meet with the highest difficulty score in the world. This time around, all of the gymnasts seem to be legitimately age-eligible.
5. The bubble teams
The top eight teams at worlds automatically qualify to the Olympics, so this meet is all-important to the countries that often end up ranked fifth through 10th. Home team Japan placed fifth at last year's world championships and is led by world bronze medalist Koko Tsurumi, a Tokyo native. Great Britain, seventh last year, will want to secure a spot in front of its home crowd in London next year. Beth Tweddle, 26, is Britain's answer to China's He on the uneven bars -- after He fell last year, Tweddle won the title. Australia's first world champion, Lauren Mitchell, earned gold on floor last year. She'll try to help her team improve on its sixth-place finish in 2010 and could win beam or floor in the event finals.
The Netherlands, Brazil and Canada would have each missed the cut last year, but could make top eight at this worlds. Canada's Peng Peng Lee does some of the coolest beam moves of anyone: She mounts with flairs à la men's pommel horse and does a switch leap, side aerial to back layout combination. Brazil's Daiane dos Santos was the 2003 world champ on floor and still tumbles the skill named after her. Though she often has trouble staying in bounds and probably won't challenge for a medal here, the energy and power she shows are well worth watching.