I am currently a junior division 1 800 meter runner. This is my first year doing a fall base training phase with the cross country team at my University. When I started with the XC team I saw gains in my PR's at 5k and my times in longer workouts increased very quickly. About 4 weeks ago when i started doing runs and workouts they seemed a lot harder than they were at the beginning of the year and now I am at a all time low. When I do any run or workout i feel good for about one rep but then my legs just feel so heavy that I can't lift them and I feel like I am just dragging them along. I took a week rest already and that did not fix this so I do not believe I am tired. Is my next step to get a blood test and see a physician? What do you guys think this could be?? I really need your help I am a serious runner and this is a serious problem for me and I just want to get it solved so that I am right for the season. Please and Thank You to anyone with useful insight.