The top-heavy stars are both suffering severe back pain ahead of tonight's semi-finals.
One Show host Alex, 34, has been prescribed strong painkillers ? and is having daily sessions with a physio.
The BBC wardrobe department are also sewing sports bras into her spangly outfits to support her 34D chest.
Alex's spine is particularly sore after hours practising the bouncy steps of the salsa with partner James Jordan.
A show source said: "Alex has got a gorgeous figure but big boobs do cause back ache. Her back is really bad at the moment. She's been suffering for a few weeks now but she is embarrassed and doesn't want the sympathy vote."
Last week Alex danced through the pain after bruising her ribs when James lifted her.Back problems ... Chelsee Healey
Actress Chelsee, 23, has been strapped up to ease the pain from her 32DD boobs. The Waterloo Road star wrote on Twitter: "My back is in bits can't walk never mind dance!" She also tweeted: "I'm in agony with it, just need to rest up tonight. Still really sore, got a heat pack on it."
But judge Bruno Tonioli warned there can be no excuses. He said: "Injury or not, you have to go for it.
"It's like doing the marathon ? the last mile is the most important. It's too late for moaning and groaning."
Alex and Chelsee are up against Jason Donovan, Holly Valance and McFly star Harry Judd in tonight's semi-final on BBC1 at 6.30pm.