I have to admit I have. Most likely, if you're reading this post, you're a runner, triathlete, cyclist, or in some way active and fit or working towards fitness. Imagine now, that you're not an active person and you sit in the same position, day after day, week after week, month after month. Not a good picture, huh? Sitting at a desk and working on a computer all day is often the culprit and cause of bad posture. There are a couple of reasons for this.
First, if you're not active and exercising during your non work time, then you're not going to have the muscular endurance to sit all day. Yep, that's right—muscular endurance for sitting. Your core muscles, such as the erector spinae muscles, the rectus abdominis, transverse abdominis, latissimus dorsi, and oblique muscles are mainly made of type 1 muscle tissue. They're the epitome of endurance muscles because they're always "on" working to keep you upright as well as to hold in all your "innards!" Well, if you're not actively working to keep your core strong, then it can take a toll on those muscles and eventually gravity wins and you begin to slump (usually forward in the direction of your computer screen). [Click here] for a good workout for your core using a medicine ball.
Secondly, because you spend so many hours in the seated position, you can get tight hip flexors. There are several muscles that make up the hip flexors most of which originate on the ilium (your hip bone) or pubic bone and insert at various places on the upper and lower leg bones. These muscles help you flex at the hip. When you sit, you're actually in a flexed position. So, after 8-10+ hours of being in this flexed position, your muscles tend to stay flexed when you try to stand up. That's a big reason why you're slumped forward when you try to get up. Eventually you're able to loosen your hip flexors and stand up. Over time, however, you can actually start to have a slight forward pelvic tilt. Over even more time, that tilt can become even more pronounced.
Good news is that most people can correct and/or prevent this just by strengthening their core and adding hip flexor stretches and exercises to their daily routine. As a runner it's vitally important to have a strong core. Your core is the source of all your running energy. A weak core will allow fatigue to set in much sooner than a strong core. Once your core gets fatigued, you'll begin to lose good running form. Once you lose your running form, that can spell disaster in a race.
Also, as a runner (who may also be working a desk job for many hours a day) you need to remember to "unflex" those hip flexors. Not only do you need to take a break periodically during the day to stand up and stretch, you also need to do the same before a run. Before you begin a run (especially after a day of office-sitting), be sure to do some dynamic stretches (actively moving stretches not static stretching). This can be as simple as a very easy light jog around the parking lot. Other times (if you're going for a longer or more intense run) you may want to do a series of simple running drills such as high kicks, butt kicks, side shuffles, karaoke shuffles, etc. Not only will this warm-up your muscles, it will also get your heart pumping and your blood circulating to all your muscles before your run.
Below is a clip from LiveStrong showing three good hip flexor stretches. These are great for during the day, at the end of your day, or after your run.
Running cold on a stiff body can spell I-N-J-U-R-Y real fast, so take a few pre-run precautions. You'll be glad you did come race day, when you're injury free.