Probably not enough running practice especially on uphill course. Me too - I don't practice uphill route and have to spend 7:38 mins to complete the 1st Km^.^
I am ok on uphill and i am fine on the first 1KM run. But my problem was after that. Even i slowed down, my heart bit rate still the same as my uphill run. Should i have a medical check on my heart?