I don't want to bore you???....
....I'm 43. At 39, I got a major injury, and took a long time off. Since then, I've gradually become stronger, but I have found that I CANNOT do any significant amount of road running, or higher training volumes. I have decided to train only for middle distance, and never worry about 10km races again. I am not being defeatist. I know myself very well. Even hard interval sessions cause me grief. I decided that rather than doing a whole lot of hard running 1, 2 or 3 times a week, I will do a little bit of hard running every day. I personally feel that this was an absolutely brilliant decision!!! :)
How best to arrange it? The 3200-200-1600-100-800-50-400-25 is my solution. Average 800m per day hard. Tasty runs every 2nd day with "excuses to warmup and cooldown" on the inbetween days. A warmup is usually 4-5k jog with many strides. This in itself is good training. :) These hard efforts are all "2x to 4x pace". ie 400m at 800m to 1600m pace, or 1600m at 3200m to 6400m pace.
I used to run more, but never beyond 60MPW, usually 45MPW.
Irregardless of my injury / comeback issues, I am convinced that "weekly volume" has become the #1 training aspect for most runners. IMHO, this is an incorrect view of training.
I ran a 4:33 Mile this year.
Cheers, and thanks for asking.
Skuj