When discussing specificity, many coaches state that it refers mainly to mimicking the conditions of the event. This is accurate. For example, if you run the mile, training must be specific to the mile and the speed of running the mile. However, there is much more to specificity of training than these two factors.
In essence, all aspects of training must be very specific. You cannot just say that you should keep your long runs at the upper end of the given range of time. This is not specific — the run should duplicate exact conditions, i. e., the exact duration and the exact speed.
If you are training to get in condition or simply working on increasing your mileage or distance, then you are still in general training. However, the training could be specific if you run at race pace or faster but for a shorter distance. Then your training would be to increase the duration of the training to run at that pace as needed for a particular race.
Specificity also refers to training the physical qualities involved. For example, in strength training, you should develop the strength and/or muscular endurance of the muscles to be able to function as needed over the distance at the intensity or speed that you desire. In essence, you duplicate the exact joint actions in your strength training so that you develop strength exactly the way it will be displayed in your run.
This is the most common use of specialized strength exercises. The exercise duplicates the neuromuscular pathway witnessed in that particular joint action. In other words, you develop strength as it is displayed in execution of the run at the particular speed needed. This is also known as dynamic correspondence or conjugate training.
Both of these terms have come to us from the Russians who did much research and practical work in this area. In fact, specificity of training is now believed to have been the secret to their success in the 1970s and 80s. But as brought out in previous blogs, this specificity has specific criteria. It is not just copying distance and speed.
See Explosive Running and Build a Better Athlete for more information on specificity of training as relates to running. You may also be interested in reading Secrets of Russian Sports Fitness and Training. It is a very detailed book on the entire Russian (Soviet) system of training that was the basis for their success.