5K improvement

Hallam Blue

I'm trying to estimate what improvement in my 5K time I could expect? I have a month to set a time (for Marathon Talk's Jantastic, incidentally). I've just run a PB of 26:05 at Marple parkrun: the course I will be targetting a new PB on the last Saturday of March. Today's run was pretty flat out (for me!) - struggling to hold on for the last mile or so. I have reduced my times consistently by 20 seconds or so every week for the past 6 weeks or so.

I'm going to follow a brief Smartcoach schedule (1 speed or tempo session; 2 shorter easy runs, 1 long run, 1 or 2 cross-training sessions a week). What I am wondering is what might be feasible in this relatively short time. Could I take a minute off in that time?