While looking at the data for my recent marathon it became clear quite quickly that something was wrong.
Here is the data for the last workout I did, one week before. This was a 10km run at marathon pace. So I averaged 4:05 min/km and my heart rate was low 160’s bpm.
Now looking at my marathon attempt. I adjusted my planned pace to aim for around 2 hours 55min finish. This equated to running at 4:10 pace. So running slower than the week before. Look at the heart rate, I was sitting at low 170’s, about 10bpm higher. It was clear I would not finish well right from the beginning.