Dr Tom Little has been appointed as the club's new head of sports science.
Little replaces Nick Davies, who has joined former Blues boss Chris Hughton at Norwich City.
The 36-year-old has a wealth of experience with different football clubs, including Manchester City, Nottingham Forest, Bolton, Sheffield Wednesday, Burnley and Huddersfield Town.
Over the past two years he has also acted as a consultant at international level with the New Zealand Football Federation.
He has previously worked for Blues boss Lee Clark during his time as manager at Huddersfield.
"Tom is very good at what he does and gets the players extremely fit which is important for the way I want us to play," said Clark.
"He’s obviously worked at all levels of the game - Premier League, Championship and League One. I think Huddersfield were sad to see him go, but they made changes at managerial level. We look forward to him being part of a successful group at Birmingham City."
Clark admits he was disappointed to see Davies depart, but understood his decision, adding: "Nick was very good and that’s why he’s been headhunted to go to the Premier League. I get on with him and think he’s a terrific lad. I wish him all the best, but we go forward with Tom now."
Little himself is relishing the opportunity of linking up again with Clark.
"I worked with Lee for a year at Huddersfield during the promotion year," said Little.
"He's a very driven young manager and a very good coach. I know he is looking to play a brand of high tempo and entertaining football and that certainly suits a fitness coach.
"Behind the scenes things are already run fantastically in the sports science department here so I won’t be coming in and reinventing the wheel. I’ll just be looking to tweak things a little bit and put my imprint on it.
"When you’re dealing with this level of footballer the real key is injury prevention and making sure they’re available for the gaffer to pick. We can’t control every element of that but there are facets we look to control and improve."