If you are spending long period of time in the wrong position you will develop tightness in particular areas that then become problematic during training. These tight areas are more susceptible to injury as well.
If you are sitting down for long periods of time ensure that your desk, chair and computer set up is correct. Even if you are stuck at a desk, sit in a position that reduces the amount of impact. Sit up nice and tall, chin back and shoulders down. This can take the tension off the areas of weakness.
Even if you are in the perfect position make sure that get up and walk around and stretch.