Brisk walking at 8.6km/h

Today's training is to try to brisk walk as fast as possible. I go through the usual route of Stirling loop.



I started very fast, almost 10km/h. But I can't keep the brisking pace for more than 1km. After the first 1.2km, my pace dropped to 7:00+. But the overall pace is still good at 6:59. I know I cannot sustain a 7:00 pace. So far, I can sustain a 7:30 pace but not 7:00. I hope I can have better technique to move my pace to a sustainable 7:00.