Did you have to look twice at the title? I did. I thought my little word play had backfired on me for a second. What one thing do we do every day that kills our metabolism, kills our immune system, makes muscles tight and stiff, and eventually cuts years off of our lives? Sitting. We sit at the house, we sit in our car on the way to work, we sit at work for 8 hours, get back in the car and sit, go home and sit on the couch for a few hours and do it all over again the next day. It's a big reason we have an epidemic of overweight people with back problems. Too much sitting shortens your hip flexors, short hip flexors cause back pain, back pain sucks. The circle of life.

Why hath thou forsaken me?

You see that red part? That is where the rhomboids are located. Why do you care? Because one of the the main functions of the rhomboids (rhomboid major for you sticklers) is retraction of the shoulder blade AKA keeping your shoulders from slumping forward like a caveman and/or cave woman. The more we sit the more our rhomboids weaken and the more our shoulders round forward. Look at the majority of people who work at a computer all day long. Or even look at yourself. If your shoulders are rolled forward and slumped forward there is a good chance you have weak rhomboids.
I saw a study a few years ago this airplane scientist did. He probably had a name and a cooler title than airplane scientist, but I forgot it. Sorry I know you were all wanting to run out and thumb through airplane research.  . This guy normally studied the effect of wind on airplanes, but he took his scientific thingies (name, forgot, sorry) and put them on people to study their movement to discover why some people were overweight and some people were not. Do you know what one activity the people who were overweight did more than any other group? Sat. The normal weight people sat a ton less and moved a lot more. Now I'm sure nutrition played a big role as well, but so does moving and standing. You can burn 100 calories just standing for an hour. So cut that sit out!