The answer to this question is probably one of the hardest to answer for any athlete. More often then not, it is very difficult to answer this question without a visible injury, x-ray, or MRI. Now, before we get started, let's make sure that we know the difference. Muscle soreness is caused from overuse and the breakdown of the muscle fibers. Similar to this soreness, a muscle pull results from damage to the muscle fibers themselves but is more serious and may require some rest for the damaged muscle fibers to heal properly.

Why is this question so hard to answer with an easy explanation? Because it is very difficult to identify the difference between normal soreness and a "pull." Everyone has different thresholds for pain, so one person's soreness may FEEL like a pull, and vice-versa. As a result of years of training, athletes will learn to know the difference between when they are sore, when they have experienced a pulled muscle or, unfortunately a more serious injury. If you are a relatively new athlete, and not fully in tuned with the difference between normal soreness and a more serious injury, don't worry, there are a couple of questions that you can ask yourself to help narrow it down.

1. Have you raced, or done a best effort workout recently?

Chances are that if you raced within 24 hours of feeling this pain, then you are probably just experiencing normal soreness. In this case, your best bet is to focus on some active recovery, to get your muscles moving and the lactic acid flushed out of your system.

2. When did the pain first appear?

If you experience the same pain during most, or all of your runs, that does not seem to fade from one day to the next, then you may be battling a muscle pull/strain, or other type of injury. This should be addressed immediately, with rest, and a plan to fix the problem. Sometimes that fix requires only rest. Sometimes it requires more involvement, be it with physical therapy, or a visit to your doctor. Conversely, if you are experiencing muscle pain, which seems to improve from one day to the next, then you are simply dealing with soreness.

If this doesn't help you to narrow it down, then you may want to err on the side of caution, take a day off, and then proceed from there. Muscle soreness is a normal side effect in the sport of running, but it is important to do whatever is necessary to avoid a more serious injury such as a pull or tear, as they can (at times), take up to a few weeks (or more), to heal. In order to prevent a serious injury such as a muscle pull or tear, it is important to train smart and make sure that you are fully warmed up before workouts, are continually stretching any areas that have an imbalance, and most importantly getting enough sleep to give your muscles the opportunity to repair themselves. Remember, your body takes care of you by allowing you to participate in the sport you love, so it is important to take care of your body as well.