What is the logic behind mixing longer runs with shorter runs?

[Ray801]

On the programme I am currently following each weekend I have a long run say 75 minutes. This will be followed by 45 minutes as the next run which is then followed by a mix of tempo and easy totalling 46 minutes then the next weekend is 90 minutes and that is followed by two 30 minut runs and so on.

I'm sure there is some science behind it, can anybody explain?

Thanks

Ray

[Bluesman]

My guess is it's psychological. After doing a long run, the shorter run that you previously struggled with seems easier, so it's boosts your confidence.

[christian1 Graduate]

I think it has something to do with muscle fibres.

running.competitor.com/2013...

[Bluesman in reply to christian1]

Hehe - shows what I know. That's a really interesting article christian1.

[Ray801 Graduate in reply to Bluesman]

Thanks Guys - good article and site.