Re: "Running Safely Into Middle Age"
It looks like the Furhman study is here to stay. It does cover the basics, and you can maintain a decent level of fitness off of 3 days a week of training, but the program is probably not optimal if you want to keep improving in performance or to maximize your efforts. Moreover, If you are either cross training on the opposite days, or running easy, then what's new? From what I've seen as a runner, coach, and student of the sport, athletes improve linearly with increased mileage through at least 40-50 miles per week. After that the benefits do taper but in general, but many runners can keep up the volume and continue to flourish with twice that.
What I've done in middle age is to actually increase mileage compared to my late 20s and 30s, while decreasing the intensity and frequency of speed work and interval training. I try to do just enough of that to keep sharp, while making sure that I'm recovered enough for races, where to me, it counts. So interestingly, my training now is a lot more like off season or early season training when I was in my early to mid 20s. It seems to work.
Ideally during the season, I like to build up to 50-70 miles per week, with a rest day every 6-10 days. Most of the mileage is very aerobic, but I'll do between 20 and 40 minutes of tempo training a week, 12-20 minutes at V02 max, and only 3-6 minutes of intervals or striders at mile pace. This formula has worked really well from the mile to 30k; marathons have proven to be tougher.
In sum, I've been there (late 30s in particular) and if I cut back to 3 days a week, even with a bit of cross training, my race times would slow by 10-15 sec per mile.