If you compare the ultramarathoners’ technique to world-class distance runners, you will see that the latter maintain effective technique with basically the same stride length throughout the race. Their running form is basically good and remains almost the same throughout the race. They do not resemble the ultramarathoner in technique.
Before you take the advice to shorten your stride, you should understand the relationship between stride length and stride frequency. For example, stride length is the simplest to increase and gives you the greatest increase in running speed. Stride frequency or turnover is more difficult to improve as it takes much greater muscular effort and nervous system involvement. In addition, there is less time for the muscles to “relax” as there is when you have optimal stride length.
The important word here is optimal stride length. Once you achieve your optimal stride length, one that you can comfortably achieve and maintain, then working on turnover becomes most productive. The faster you can improve your stride frequency while maintaining optimal stride length, the faster and further you will go. Simply shortening stride length may enable you to go faster for a short distance, but you will be unable to maintain this speed over a long distance.
A longer stride, however, enables you to go longer with less effort and with greater speed. But if speed is not important and you seek mainly distance and duration, a shorter stride may be best for you. But even here, you will usually fatigue sooner than if you maintained an optimal stride length.
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My Thought: Just concentrating on strides per minute (a/k/a cadence) is a mistake. There's a good range you should fall within (84-90+) but the key is to find the optimal stride length and then comfortably increase stride rate without shortening the optimal stride length. I see some beginners that shuffle as they run and that's fine for slower paces over a longer period of time but if you try to increase pace and maintain a shuffle type stride length, it is very difficult to do and only a few runners can maintain that over a longer distance. Many discussions start and end with stride rate and that's misleading.