Smith (23) said he needed regular rests because he is carrying a number of injuries that affected him during the Olympics.
He said: "People think that because I went to the Olympics I am superhuman, but I have a torn cartilage in my knee that needs an operation, a fractured ulna and swollen vertebrae.
"So every 15 minutes I'll have a lie-down for five minutes."
Cacace said: "I was in shock when he first curled up on the floor, pulled his hoodie over his head and asked me to give him five minutes in the middle of training."
The silver medal-winner is accompanied to training by his mother, Elaine, who also brings him his lunch most days, but the dance pro said it means both of them are able to drag him off the floor to get him dancing again.
Cacace said Smith lacks motivation. The gymnast was diagnosed with attention deficit hyperactivity disorder (ADHD) when he was a child.
Cacace said: "Unlike other sportsmen, Louis doesn't push himself: he needs someone to do it for him.
"During training, he'll start playing with the air-conditioning unit, check Twitter or stare out of the window.
"I feel a bit like his mum."