The Olympic gold medallist has previously suffered from inflammation in her spinal joints during her cycling training programme.
Pendleton is said to have asked professional dance partner Brendan Cole to go easy on her in training, reports The Sun.
"Victoria is a very driven competitor, but she also has to be careful," an insider said. "She doesn't want to do herself any more damage.
"After they were paired, she sat Brendan down and told him about her back problems. He promised to take them into consideration. But going easy on her doesn't worry him because he knows she demands so much of herself."
Professional dancers Artem Chigvintsev and Anton Du Beke have both spoken of their disappointment over their dance partners.
Strictly Come Dancing returns to BBC One on Friday, October 5, where seven celebrities will be performing for the first time with their new partners.
Photo gallery - Strictly Come Dancing launch show: