"Performance is rarely measured in just sheer volume and most often is associated with the speed of that volume." Tim Waggoner
treadmill 5 miles 35:46
Since I have been focusing on a lot of long slow distance running for ultras and long trail runs, my short distance speed currently sucks. I have done a few speed interval days, but zero mid-range (3-6 miles) tempo and time trial work. That is part of the reason my recent 5k time was weak.
When it comes to running training for most of us, the blog post linked here contains a lot of wisdom. I understand the concept of building an aerobic base to increase endurance, but that is a very time consuming (and boring) approach. Running 5-10 miles a day to get 60-80 miles per week (or more) of running in would destroy my body and my motivation.
So while it may not be optimal, I agree with the blogger in the above post - running training is a lot like weight training. It needs to be a process of specific stimulus and then recovery. A weightlifter who wants to increase his bench press will lift heavy a couple days per week, and then recover and do it again. He won't do 1000 pushups and hope his bench goes up. The running analogy isn't perfect, but to me this is the same concept as running slow for 10 miles and then hoping your 5k race time improves.
Given the demands on my time, I need a training program that maximizes the benefit for the time I put in. So what I am planning to do is add many more mid-length (3-6 miles) time trials and run only 3 days per week. I will still do a longer distance run on the weekend, but nearly every mid distance run will be close to race effort and four off days per week should ensure enough time for recovery. Since my legs are pretty tired from all of the miles of the last couple of months, this should also let them recover prior to the races I have coming up in the fall. I don't think there is much downside to this approach, as I doubt I will lose fitness this way, and I might even get faster.