Increasing your cadence is a short term answer and is very limited. Can you imagine running a marathon with your legs going as fast as they would be if you were running a 100 meters?
Your stride length increases your running speed because you are covering a greater distance with each stride. As you do not change your leg speed that much, you will obviously cover the ground that much quicker.
Your current leg speed and stride length have become habitual and so are preventing you from running any faster.
In fact, this will cause you to get slower over the years. This is for two reasons:
Once you reach 30, your muscle mass decreases by 10% every 10 years; unless you do something about it.
Also, it is the fast twitching muscle fibres that decline, not the slow twitchers.
So your stride length will decrease as you get older. As a result, you will be running slower.
Running at the same easy pace does not challenge you.
Like Emil Zatopek said; you need to run faster.
The way to stop the decline in fast twitching muscle fibre is to do anaerobic type, high intensity training like weight training, circuit training and sprinting hard.
Anything for a short duration at maximum effort in fact
Tips to Run Faster
Here are a couple of easy ways you can increase your stride length and to run faster.
Stretching is important because it keeps your muscles supple and long. Hard work tends to shorten your muscles and this results in you feeling stiff and not having the ability to stride as far.
Stretch and keep your muscles supple and you will be able to stride further and you will be less prone to injury.
If you are cross training and cycling, this is particularly important as you never even straighten you leg when on a bike, so your muscles shorten and your stride length suffers as a result.
Believe it or not, this is the method I have used to run faster, with great success, over that last year or so.
It is so effective that I am running faster now than I was 10 years ago.
But don’t think you are going to have to do some weird meditation routine: it’s far simpler than that.
When you are running, especially when you are feeling tired, think about increasing your stride length and reducing your cadence. Push back harder with every stride and take fewer strides to maintain your pace. This is what you need to do to run faster, so you need to start doing it consciously before it will become unconscious.
You will probably not be able to do it for long at first, but as you get more practise and the habit starts to become engrained, you will build up the strength to maintain the longer stride and you will run faster.