I've just bought Joe Friel's book. I don't know when I've been so fired up by a writer. I think it's because he is insisting that a large proportion of supposedly age-related slow-down is due to our own behaviour, so we can do something to resist and maybe even reverse it. Mark G mentions Friel's idea of the 9 day training week, but the advice that grabbed me was (1) to do vigorous speed work and (2) to do heavy weight training, rather than slipping ever further into gentle lsd. This will supposedly do great things for our hormones, telomeres etc. It's too soon for me to report any results, but after my first attempts at very short intervals à la Friel I certainly FELT different! Now all I need is a parkrun pb.