After reading my blog on the amount of mileage needed to achieve a good running time, I received an email question on how much can one person expect to improve in a given season or year?
Quick answer, ten percent is probably the max. I say probably because if you are new to running, say 2 years or less, each race you run could be 5 to 10 percent better than the last until you finally settle in on your real 'max'. If you are an experienced runner, you would be ecstatic if you could achieve a ten percent increase each year.
What do I mean by ten percent? Ten percent would be in relationship to time. So let's say that your last Half Marathon was 2:12:00. The total minutes for this distance are 132 minutes. Ten percent of this total is 13.2 minutes. So an improvement of 10% would be 132 – 13.2 minutes = 119.8 minutes (or 1:59:48). So running a sub 2 hour Half Marathon at the end of a season after running a 2:12 marathon in the beginning of the season is possible. Possible but not without a focused determination to achieve it with a dedicated plan.
It's never a bad idea to set two goals at the beginning of a season. I always have two goals based on my first race. The first one is a 5% increase and the second is a 10% increase. Early in my running experience the ten percent goal was achieved easily. Now, I'm happy if I can achieve the 5 percent. Some of that comes with age, but I account for that by using my best time early in the season to now determine what a realistic 5 and/or 10 percent should be.
Don't set yourself up to fail by setting unrealistic goals. Give yourself a goal that is challenging but reachable. It will keep you looking forward to your runs instead of dreading them.