Jan Ransom's comments come as a government-commissioned review said women could be allowed to serve alongside men on the frontline by 2016, after finding it wouldn't have an "adverse effect" on troop unity.
The Defence Secretary, Michael Fallon, says combat roles "should be determined by ability and not gender".
He's asked for more research to confirm women are able to physically able to cope with the demands of being on the front-line, and perform full six-month tours. The findings of this research are expected in 2016.
Women are currently allowed serve on the front-line, as long as the primary aim of their role is not to "close with and kill the enemy".
They already serve on the front-line as medics, engineers, intelligence officials and in other support roles.
Jan told Premier's News Hour: "I have some concerns about the physical aspects - of the girls being able to carry the weapons, to be able to carry the weight that they have to carry.
"I think sometimes the men would struggle with it to be frank.
"It's there mindsets that also need to be helped, trained, encouraged, to be able to accept the women alongside them.
"Sometimes it would be tough on the women being accepted.
"There is a sexist issue, but here I am - a retired Lieutenant Colonel - saying I have some reservations. That's not a sexist issue, that's just my gut feeling.
"I think mentally they're well capable of doing it. I don't think their mind is the issue.r many women, it would be the physical aspects that would be very difficult."
Lieutenant Colonel Jan Ransom:
