I've been running for two years and have not performed intervals before. I never had access to a track. Instead I do a tempo run each week, ranging from 20 to 60 minutes and pace 6:30-6:50. All of my other runs are 7 or 8 minute miles on 40 miles per week. PBs are a 5k of 18:41 and 10k of 38:22.
I feel like I have never gained any speed or fitness from tempo runs. However, when I have done a 5k time trial (which for me is 6:00 to 6:05 pace) I feel faster for a few days. I'm starting to think that I only respond to threshold running or volume of running, and tempo runs are neither here nor there.
Can anyone offer imput on this? I'm thinking of dropping my tempo run for some 400m repeats on a quiet road.