Two things tend to happen when your stride rate drops. First, you try to reach farther to create a longer stride and end up overstriding. Second, you either spend a lot of time every step planted on the ground where you have a finite distance you can move or you spend a lot of time every step airborne, which results in large amounts of vertical motion. Both of these result in wasted energy.
While I don’t like focusing on a specific number, I do agree that, within reason, a faster stride rate is better. A lot of fast runners fall into the 180 strides per minute (90 steps per foot per minute) range, so that has become the popular number. I’m sure not at all related to it being a nice simple number of 3 strides per second. 😛
So, what do you do if you have a low stride rate? If your stride rate is 120 steps per minute (60 steps per foot per minute) I would suggest working on increasing your stride rate. However, don’t do so by simply thinking “take quicker steps”. Do so by training your body to take quicker steps. Form drills and strides are the cornerstone of training for this. If you’re not familiar with these types of training, you could either Google them or ask and I’ll try to give a more complete explanation of them this evening when I have more time if nobody else beats me to the punch.