I've been running for seven months now, averaging 15-20km a week. I love it and I am excited to be doing the British Heart Foundation 10km in Hyde Park on Saturday, but I am very aware that I don't seem to be getting any better. As my distances have increased, my 5km time has increased too (I know others have experienced this), and I feel I am a bit stuck. Has anyone had experience of using a heart monitor to keep your heart rate at optimum level, and has it helped you to increase your fitness? Any other tips on taking my fitness up another notch?