I am a 57 year old male and was a late starter (running 5k, 10k and marathons for nine years). I have read that my times could improve up to the age of 55 and start slipping from there on. So far it has proven true. I have been very careful not to respond with harder training which could lead to injury. On the flip side I don't want to be too conservative. So how do you guys know when to lower training and racing expectations without using injury as an indicator of diminished ability?
not certain about the question. It seems you started at age 48. supposedly there is a 5 - 7 year improvement window if you train on a consistent basis. I don't think you can know for certain if you're being too conservative. That is the art part of running. If you don't get injured then try more. If you keep getting injured then do less.
I've found that as I've gotten older (and I'm about your age, started running in 1970), I perform better on less work, e.g., 45 - 50 mpw in 6 days vs. 60 - 70 in 7. If you find yourself dragging in workouts, you're probably trying to do too much. Better to err on the conservative side.
It's VERY important to avoid injury, because you never quite get back to where you were. I'm about 8 years older than you and after recovering from a long injury, I discovered that my max heart rate had declined. Of course, my LT went down as well. My situation might be totally unique, but when in doubt about an injury I abort the workout and walk home.
One workout is never more important than being able to run the next day. ...and the next week... and the next month. I lost a month back in September due to a back injury and it has taken 3 months of Very hard training to get back close (but not quite) to where I was before the injury.
Recovery also takes longer. Using the stick or foam roller helps. LOTS of sleep helps. You also need to do everything you can to slow the aging process. It won't help your performance this year, but it will keep you from slowing down as much as your peers over the years. Get your thyroid checked. Lift weights to boost your testosterone levels. This is more important with age because lifting boosts T levels. Lift heavy and to complete exhaustion until someone comes over and asks, "Are you okay?" Do extremely hard hill sprints... again, it's been proven to boost your T level.
You can't train harder, so eat smarter, train smarter, recover smarter, and take control of your health and age slower.