Without being too extravagant about it, I've probably been trying to lift the foot a tiny bit and put more into each step recently to see if I could increase my pace by a fraction. Not a major focus, but just a minor thing to think about while running. I've probably found myself picking up a little bit of pace on short (3km) runs, but not being faster overall on longer runs. The one major difference I have noticed is that I seem to fatigue faster and my calves have started to flare up. I'm not sure if this is the slight form change or the fact that my mileage is catching up on me (I'm still ramping things up slowly), but this gives me plenty to think about. My last run I went back to my old thoughts of being efficient and not doing anything special with my form and it probably felt better all up.