I'm just getting back into the gym I've been out since last June with a back injury and I've noticed that after a hard HIIT session on the eliptical that I begin to feel fatigue and eventually develop flu like symptoms, sore throat runny nose and a little cough Thursday I did my hardest HIIT session yet after a massage on Wednesday and immediately felt like I was getting sick and by Thursday night it was full blown but it doesn't last long like um feeling better today. Anyone else experience anything like this?