Running in Reverse

Due to some concern about my left hamstring and general boredom, I decided to try and mix things up by running Prospect Park in the reverse direction I usually take. This seemed like a good idea to compensate for the slope in the road as well.
It was so hard I couldn't believe it! I don't know if running the generally hilly route in reverse was so difficult due to it turning into a steep decline followed by a long, gradual incline, or by the complete erasure of my mental marks (Oh here we are at half way! Just up this big hill and you're almost done! This is the yield sign where you sprint to the finish!)
It felt just as terrible as the first time I ever ran the park, several years ago, in the snow, coming off of a cold, when I was convinced it must have been MUCH longer than 5k.
How running in one direction has become so easy, whilst running in the opposite direction seems positively masochistic is beyond me, but I am determined to conquer reverse Prospect Park again this weekend, as well as a longer 10k run on the West Side Highway running path, which will be new territory for me. Wish me luck!