I think the combination of the half mara on Saturday and the 3000m track race on Monday with the 100 mile week enabled the sinus infection to take hold. I've pretty much had sinus problems since my early 20s but the last 5 years they seem to be recurring with a greater frequency. Two a year on average now.
If there are any runners who also suffer with sinus please let me know as I'm still not sure what brings it on and how, if possible, to stop them from happening. This latest one was no fun at all, I had a phlegm blockage that had my nose looking like Arnies' in that scene from "Total Recall" when he was trying to pull that tracking device out of his nostril (see below)!
Anyway, back to the training this afternoon.