Flu symptoms after interval training

neil4ad

I've been coming back from an ankle injury, and therefore, have been using treadmills at the gym of late. I notice that if I run at a normal steady pace, I have no problems and feel good after.

If, however, I try to do interval/sprints (run at 6mph for 3 mins, then increase speed to as fast as I can go for 1-1.5 mins, back to 6mph for 3mins, and so on) after about 22 mins, I get off the treadmill and am sneezy, with severe runny nose. I've tried this twice and both times, I've ended up having to take 2 days off with really bad cold symptoms.

Is the onset of the cold -- if indeed that its what it is -- due to overtraining? I'm wondering alternatively if I might have caught something that has been lingering and that flares up when I raise the intensity of my workout.