Here’s my favourite.
What’s your fastest 5k?
Let’s say 20 minutes (nice respectable round number, just for illustration the article applies to all levels). That is 4min pace ie 1km in 4.00 minutes.
So your training today is:
5 x 1km @ 3.55 pace (ie a ‘bit’ faster but not for so long each time)
You can rest in between those intervals for as long as you want. But no more than 5 minutes. You can even stop if you want to. The more you stop in between the sessions of effort the easier the whole thing is, so you will gain most benefit by doing the OPPOSITE ie the hardest/most beneficial would be to have a 1 minute jog recovery in between the 1k repetitions.
This one WORKS. IT WILL MAKE YOU FASTER. Just combine it with distance work and you need not do anything else. But it is hard so you MIGHT want to do something else to make life easier for you!
Not suitable for absolute beginners. Adjust the target pace to be slightly better than a recent 5k PB.
Of you go then ! Good luck.