At week 4 I don’t think you have enough data to determine if your pace is improving. I just started week 8, and while I notice a minor increase in distance, I am also spending a little more time on the track. Time on the track varies up and down through the program, and time walking versus running does too ( though later running is only going up). Seems like day 1 of each week I deliberately slow my pace, so I have enough wind to run through the run phases, however I seem to mostly increase my distance over time. It has been, for me, only 22 days on the track, and I have good and bad days. My pace goes up and down day to day, but my endurance gets better every day. Once I am running 5 k regularly, I expect my pace to improve logarithmically, I.e., steep gains initially that plateau as I reach my body’s best.
