Am currently training for a 10k in 3 weeks time - this week I covered 9k in a fraction over one hour (interval running). I have recently slotted in a couple of 5K's, just to give my limbs a rest from the longer runs. To be honest, I expected to breeze though the runs but am bit shocked to find I'm a good couple of minutes off the 5K pace I was covering in March, before I started extending my distance. Is this common, or have I done something very wrong in my training? Starting to think I haven't mixed things up enough!