I don't mean raw speed (i.e 100m dash time), but more stamina related (mile, 3k, 5k distances). That being said, I seem to have a big problem at doing any speedwork at 5k pace and below. As I mentioned, my endurance seems to be in a pretty good spot right now, but I just can't get any speed to show up. For some background, I have put in several 100 mile weeks over the past few months and can do 10-mile tempos at 5:50ish pace pretty comfortably and cruise along at 6:00 pace for 14 miles within a 22 mile long run (I'm training for a marathon BTW). But whenever I try faster workouts, like VO2-max intervals, I get a huge sense of inability. Anything under 5:20 pace feels very fast, and 4:40 pace it feels like I'm pretty much sprinting. Based on the marathon pace I'm shooting for and the tempos I can do, I would think that I could come close to 16:00 flat for a 5K, but when I do a 5K-paced workout, I'm barely scraping by at 16:20-16:30 pace. For example, today's workout I did 3 x mile, and 3 x 1000 with 2:00-2:30 rest in between, and hit 5:15, 5:13, 5:16, 3:16, 3:18, 3:17 and it just felt like I could not go any faster. It makes me think I can only run 17:00 for a 5K when I should really be closer to 16:00. Honestly, I feel that I should be able to run close to 5:00 flat pace for these intervals and feeling good. Am I doing something wrong, or is it normal to not be 100% "sharp" when training for a marathon and putting in high mileage? I'm going to focus on 5K-10K for a little while after the marathon, So what can I do to feel more relaxed while running faster paces and hopefully bring down my interval pace closer to the 5:00 flat range? I know speed doesn't really matter for the marathon and this isn't a huge deal right now, but it's still frustrating and it feels like it's going to really limit me when I do try out shorter distances again.