A very popular but erroneous recommendation to runners is to shorten the stride for faster and more economical running. According to the coaches, the most common mistake distance runners make, especially beginners, is that they overstride. As a result, they believe that you will tire out faster and increase your risk of injury, mainly because of the greater jarring that your body will experience.
On the surface this appears to be a sound recommendation. However, unless overstride is defined and explained it makes little sense. Because many authors and coaches now recommend not overstriding, it has become “trendy” but yet, no one has defined what is meant by the term. In spite of this, they recommend that you not do it, whatever it is.
Technically, overstriding means that your stride is longer than what it should be in optimal conditions. When you stride is longer than “normal”, it will interfere with your running mechanics and create the illusion that you are leaping rather than running. Thus when an individual overstrides it becomes quite obvious.
Some coaches even maintain that overstriding occurs whenever you land on your heel. However, this may or may not be true. If we stay with the above definition the important thing to be considered is how long the stride is, rather than how touchdown or what part of the foot makes ground contact first. Thus you can land on the heel of the foot when the leg is far out in front of the body or only 12 inches or so in front of the body. This is really immaterial except as it relates to running efficiency and as a possible cause of injury.
Thus it is length of stride that is the key factor. There are many runners, including many high level and elite runners, who have touchdown on the heel well in front of the body or close to the vertical projection of the center of gravity. But they are not overstriding since the length of their strides are basically optimal for them.
Also if you maintain a constant running speed then it is doubtful you are overstriding. The proof for this would be in your times for a particular distance using a shorter stride and your normal longer stride. If you are running faster with your normal stride you are not over striding! If your normal run is slower with a shorter stride then, length and your stride to improve your running speed.
Many studies have shown that stride length is the key component in running speed. Stride frequency is of course important, but mainly in sprinting. But even in sprinting, stride length is usually more of the determining factor in speed rather than frequency. In other words, the runner develops maximum or optimal stride length and then works on more stride frequency while maintaining stride length.
In regard to overstriding, especially in long distance runners, I have yet to see a definition of overstriding and how it can be recognized. No one has done any studies to determine what stride length is optimal for a particular leg length, body height, or speed of running in relation to running technique. Because of this how can anyone make sound recommendations about overstriding when we not only do not know what it is? How then can recommendations be made to increase stride frequency and decrease stride length?
For more information on the relationship between stride length and stride frequency see Explosive Running. It has excellent detailed explanations of these two speed determining factors together with sequential pictures taken of high level runners to show how touchdown should take place in the most effective manner.