Runners have to be acutely aware of the difference between soreness, which is a direct result of hard training, and pain, which is a result of injury. Any runner who has been running for some time is quite accomplished at blocking out pain, we do it all the time to get through tough workouts. So it should come as no surprise that we are quite good at blocking out pain from an injury as well. We can delude ourselves through all sorts of arguments, and if we are not careful, ignored pain can turn into a major injury.
I spent the better part of last week sore from my workouts. Coming off a two week hiatus I was eager to get back to full time training and I pushed a little too hard on Monday. Each subsequent hard workout for the week pushed me further into muscle debt and by Friday it was almost a full 5 miles before I felt "normal" on my run. Despite this, I pushed through the week as I knew that the soreness was a direct result of the ramp up in mileage, and that with my mileage base I would be back to normal after a good rest day. This week has been much better as my body reluctantly adapts to the renewed intensity of training.
That being said, if I experience pain that I feel is due to a potential injury I usually will return to rest almost immediately. For me there are several markers that I look for to differentiate pain from muscle soreness. First, is the pain acute or spread over a large region? Acute pain is never a good sign as it is usually due to a localized effect (either muscle or bone), while soreness is spread out due to muscle damage from training. Acute pain almost always sends me to the freezer for an ice pack and a prescription for a few days off. Second, is the pain aggravated by running? Soreness and tight muscles may feel pretty bad when you first start a run, but symptoms will often improve as you get warmed up. An injury, on the other hand, is usually made worse by running, so if the pain is nagging throughout the run or if it alters your gait in any way, pack it in early. The third marker is persistence. Living with soreness is a fact of life, but usually we know intuitively when pain does not fit that mould. Does the pain persist through the day after the workout is over? Is standing or sitting in a usually comfortable position now uncomfortable? Worst of all is dull throbbing pain that exists without any movement at all, a clear warning sign.
Making the decision to take a few rest days or even rest weeks during a training schedule is never easy, but it is essential that you listen to the signals your body is sending you. A little time off now can save you from a major recovery period down the road. Above all it will keep you running for years to come, and racing another day!