Sitting at a desk all day will make your bottom flat, flabby, and saggy.
That is a fact, according to New York-based personal trainer Dan Giordano, of Bespoke Treatments Physical Therapy.
No amount of weekend workouts will offset five days of inactivity, he warns.
And after five years in an office job, he says it's likely the damage will cause the muscle in your derriere to start wasting away.
It all comes down to two things: lack of blood flow and the way most of us naturally sit.
Worse, Giordano explains, the strength of your glutes (gluteus maximus - the muscles in your butt) impacts your pelvic stability, pelvic rotation, and your core.
It means it's not just your butt that will be affected, but your entire workout and physical strength.
1. YOU'RE PROBABLY SITTING WRONG
"In most office jobs you're not moving so you're getting stuck in a position - and usually it's not a correct position," Giordano explains.
"Ninety percent of people sit in a way that means their pelvis rotates forward, putting pressure on your spine.
"And because you're sitting for hours at a time, you're not activating your glutes.
"That is going to cause the muscle in your bottom to lose its tone and shape and not be as firm.
"Think about it: if you have a round shaped bottom or a muscly one, and you don't work it out, it becomes flabby and its sags.
"So if you're in this job for five years, you could atrophy the muscles."
2. YOUR BLOOD FLOW SLOWS DOWN
"When you're sitting at your desk for a long period of time you're not moving your blood flow,' Giordano says.
"We all know this: if you're sitting for a long time, you become foggy. If you're sleeping for a long period of time your muscles seize up.
"That's because of the decreased blood flow.
"This could affect your muscles because you're not getting blood flow.
"It means certain muscles, like your glutes, are not activating. It's also going to take you longer to warm up when you work out."
1. WALK AROUND - EVEN FOR 30 SECONDS
"You need to just get up and move. If it's only 30 seconds, that's fine, that's something," Giordano urges.
"It is so important to keep your blood flow moving and keep your muscles as active as possible.
"Get up every half an hour - or 15 minutes if possible. You could get up every hour but every 30 minutes is so much better.
"Go to the break room, walk around.
"You clear your head, become less foggy, get your blood flow moving."
2. GET A STANDING DESK
"If there's any access to a standing desk, get it," Giordano insists.
In Scandinavia - ranked as the "happiest" part of the world by the United Nations - 90 percent of office workers have access to standing work stations.
Studies have shown the act of standing up increases our productivity and dramatically lower the rates of obesity, heart disease and type 2 diabetes.
3. USE A FOAM ROLLER
Giordano says we should all be using a foam roller every day.
"Mobility is the number one thing," Giordano says, as he sings the praises of foam rollers.
A foam roller is a large, cylinder foam block used to give yourself a massage and ease tension in the muscles.
It is common among athletes.
But Giordano said it is just as essential for office workers.
"You should be working out, but also taking recovery days - for every three days you work out, you need a recovery day.
"But the one thing you need every day is a foam roller - 30 seconds per body parts per day."
4. VARY YOUR WORKOUTS
If you're not varying your workout, your body will get used to it, Giordano explains.
"Vary it: take some classes - do a barre class, then a spin class... change it up.
"That will help you work different muscles throughout the week.
"Also I don't think you'll be happy if you just do the same thing all the time."