I’m sure somebody has looked at this before, but this weekend, I came up with a formula to predict age-related declines in race times. I intend this to apply to athletes who start running competitively in their early teens and continue for the most part continuously throughout their master’s years. I don’t intend this to apply to guys like Carlos Lopes, Jack Foster, and Pete, who picked up running a little later in life and raced very close to their best through their late-30’s and early-40’s.
On a % basis, you’ll slow down:
Lower bound: 1.0050^(current age – 28)
Upper bound: 1.0075^(current age – 28)
In other words, every year after 28, your age related decline will be about .5% to .75% per year. Depending on age and fitness level, this works out to about 1-2 seconds per mile.
I think this applies more to shorter distances (mile-5k times). I could see somebody getting faster in the marathon through their early 30’s by having better endurance but worse shorter distance speed.
Also, this isn't meant to be an age-graded table, but a tool to track an individual's times through his racing career.
I’d be curious to hear if some of the older guys think this is a decent rule of thumb.