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With The Amazing Race boiled down to the final five teams, things are intensifying and for some contestants it's getting very dangerous.

In the featured promo for this weekend's episode, the contestants are all on edge as they scramble to finish the race. Although they want to get an edge on the other teams, Vanessa and Ralph have to take a break when Vanessa trips and injures herself while running on pavement.

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The other two teams are bogged down with fatigue, as J.J. admits that he feels like he is going to pass out while he is working and Mark is asleep on a bed with an IV in his arm with the potential of a heat stroke.

While physical health doesn't appear an issue for Brendon and Rachel, they are presented with a substantial obstacle when it is revealed to them that they'll both have to shave their heads, which causes Rachel to emotionally burst out, "I can't shave my head. I paid $500 for [hair] extensions."

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Find out which teams can survive the physical and emotional strain of the competition on The Amazing Race this Sunday at 8 p.m. on CBS.