Better to start uphill or downhill?

Another five miler in Seanféistín with Conor. Our usual route starts at the cross road in Ros a Mhíl, heading towards the mountains. A long and slow incline, followed by a straight bit, then a sharper incline, down hill a bit and then turn around. I decided to run the inclines at pace again tonight, and sure enough I was absolutely knackered after finishing the last one. I used to hate starting my run with an incline but I'm beginning to think that it isn't the worst way to start off - it gets the body pumping straight away????