Pale Rider

I didn't ride yesterday due to the fact that I had a stomach problem. After lunch yesterday I started feeling a strain in my stomach. Needless to say, my lunch, breakfast, and dinner from the night before were gone. I wasn't feeling up to riding and took it easy. Tonight was different. I am feeling better and decided to get after it. I went E. on 27 and continued on 100 S. to 250 E. where I turned S. Once I was on this road, I felt like I was going uphill because I was having a hard time keeping my speed up above 16 mph. My legs were burning like crazy and my sides were aching. I felt like giving up and taking a rest, but decided that I had to keep going. I turned W. on 400 S. and continued over to 50 E. When I got onto 50 E. I was able to pick my speed up, so that I could feel the burn in my legs. It is impossible to see the slope to the roads, but I am assuming that when I am heading S. towards the hills, I am going slightly uphill and when I turn and head back to the N. I am going slightly downhill. This is my theory, not sure if it true. Here are my stats:

Distance: 11.48 miles
Max Speed: 22 mph
Avg. Speed: 16.5 mph
Time: 41:45 minutes
Calories Burned: 589.2
Fat Burned: 75.4