If Olympic broadcasters have done their jobs right, you've probably cried — or will cry — at some point during the Olympics. They show us athletes who've trained for years, only to have their efforts undermined by an injury, a fall, or a dubious ruling. But even in such situations, these athletes often exhibit the spirit that got them to the Olympics in the first place. That's what Chinese hurdler Liu Xiang did on Tuesday, limping his way across the finish line after crashing into a hurdle and despite having no chance of winning. A look at seven of the most heartbreaking moments of the Games so far:

1. Chinese hurdler Liu Xiang repeats 2008 Olympic crash
It was a horrible case of déjà vu for Chinese hurdler Liu Xiang, who crashed into his first obstacle during the 110-meter hurdles. At the 2008 Olympics, he'd failed to clear a single hurdle, even though just four years prior, at the 2004 Games, Liu became the first Chinese man to claim a gold medal in track and field (a persistent foot injury predestined his fall from grace). This time around, he hobbled to the finish on one leg and was met by Balazs Baji of Hungary, who raised Liu's hand in the air to declare him an honorary winner.

2. A Canadian triathlete falters on her debut, finishes last 
Although a bum hip kept her from competing in any pre-Olympic races this year, Canadian triathlete Paula Findlay still competed in her first Olympics on Aug. 4, after training for a mere two months. She'd claimed to feel 100 percent but severely underestimated how unprepared she was. Near the end of the three-part race — which includes swimming, cycling, and running — she trailed winner Nicola Spirig of Switzerland by more than 12 minutes. She finished in last place and, sobbing, apologized to her supporters: "I feel terrible. I'm really sorry to everybody, to Canada. I had big hopes for myself and a lot of people had big hopes in me."

3. Tyson Gay misses a medal by one one-hundredth of a second
When an announcer described American sprinter Tyson Gay as "the second fastest man in history" before the 100-meter men's final on Aug. 5, it was likely "both an enormous compliment and a painful reminder that... no matter how hard he has trained, it hasn't been enough," says Jim Caple at ESPN. When the race was done, Gay was merely the fourth fastest, finishing behind Usain Bolt, Yohan Blake, both of Jamaica, and his fellow American Justin Gatlin. The biggest disappointment? Gay failed to medal by just one one-hundredth of a second. Tears rolling down his face, Gay, who recently had hip surgery, walked off. 

4. An equestrian recovers from a broken back, gets disqualified 
Canadian equestrian Tiffany Foster suffered a devastating injury in 2008, when she fell off a horse and broke her back. She couldn't walk, much less compete at the Beijing Olympics, but she still went to China to support her team. Fast forward to 2012 in London, just before the Aug. 5 stadium jumping event. Officials checked all the horses that would be jumping and found that Foster's horse, ironically named Victor, had a hypersensitivity in its left front leg, barring it from competing. Foster, undeterred, said, "I've come back from bigger setbacks in my career, and I know I can overcome this."

5. U.S. gymnast Wieber fails to qualify for the all-around
In one of the biggest surprises in the London gymnastics competition, American Jordyn Wieber failed to qualify for the all-around final — the event in which she had won gold in the last world championships. She proved resilient, however: Just two days after the disappointment, Wieber helped her squad win gold in the team event. It was the first team gold for the U.S. since 1996. 

6. South Korean fencer loses due to a clock error
South Korean fencer Shin Lam, a favorite to medal, had quite a rough start at the Olympics. During the fencing semifinals, an Olympic volunteer incorrectly restarted the clock, giving Shin's opponent, Germany's Britta Heidemann, an advantage. Heidemann went on to win the match. The understandably angered Shin protested the result — for an hour — remaining in the playing area to signify that she would not accept the officials' decision. Adding insult to injury, Shin later lost her bronze-medal match. When Olympic officials, belatedly acknowledging the clock error in the semifinals, offered her a special medal, she turned it down. Eventually, though, Shin got a real medal, when she won seven of her nine matches during the team event and South Korea won silver.

7. Canada's stunning loss to the U.S. in women's soccer
After 120 minutes of play, Canada's women's soccer team fell to the U.S. 4-3 on Aug. 6. Tears flowed, and some of Canada's players remained glued to the field even after the semifinal match had ended. "I just don't think any of us could believe what happened, honestly," said Canadian forward Melissa Tancredi. "We didn't want to leave because we couldn't believe what happened. That was our win. That was our game to have, and it was just taken away."

Sources: CBS NewsCanada's Chronicle HeraldE! News, ESPNGlobe and Mail, Ottawa CitizenYahoo Sports (2)