Don't run LSD. Run LED instead.

Many experienced coaches will tell you that all running long and slow
will do will make you really good at running long and slow. Do you
want to be slow? Not me!

LSD (Long Slow Distance) running is good in theory. It trains you to
be able to cover large distances. The problem is the word "slow".

When you hear that word and you train that way, you focus on going
slow and not much else.

Throw out the slow and replace it with something actually useful: "Efficient".

If you go out for a three hour LED run, you will be thinking about
efficiency. Specifically, what's the fastest speed you can achieve
while still keeping a low heart rate?

When you do this, you pay a lot more attention to your foot strike,
hip movement, arm swing, and posture. Not only that, but you also pay
more attention to your gear and nutrition.

You can apply this by trying different techniques while recording your
average HR. Compare your runs. Which ones had the faster speed with
the same or lower HR?

Most of all, just scrap the LSD mindset and go with efficiency
instead. LED all the way. :)