What pace should these be? Guidance for interval workout intensities.

As endurance athletes we sparingly do shorter duration interval training to lift the “ceiling” on our fitness. It’s trendy to say this type of training should comprise 20% of your sessions. While there’s a ton of individual considerations in that statement I think that’s a good rough guide on how much high intensity training to schedule for yourself. We offer two group interval workouts a week (a bike and run) where the workouts are designed to target a range of intensities in and around LT2 or threshold. Hard, basically.

I never respond to the question of what pace these intervals should be on the running track, and constantly caution about strictly following the power guidance on the Zwift workouts, because I can only get it wrong. What I’m aiming for in these speed/threshold workouts is a physiological adaptation to make you fitter. To raise your ceiling. And for that I believe a block intervals with a work/recovery schedule of 20-40 mins with the “work” part of those intervals at an RPE (relative perceived exertion) of 8-9 out of 10 is the best stimulus to achieve those adaptations. So why no pace goals? Because, even if I’m coaching you, have your test data and do the math on what that 8-9 out of 10 RPE should be as a pace I could get it wrong and you wouldn’t get the optimal workout in. Example, I tell you to run a 7mim/mi pace for your 6 x half mile repeats but you’re particularly rested and have made some gains in fitness since your last test or race and that turns out to be a too easy effort (like a 7/10) and you ended up not in the right zone to be effective as if you’d just gone out and run a 8-9/10. Conversely you arrive at the track on Tuesday after a huge weekend of training and some poor sleep and 7min/mi feels too hard and you give up after the 2nd rep because you can’t hold the goal pace. Again, you would have been better off going on RPE and getting the full set of 6 intervals in that still felt hard and pushed your heart rate up and got those adaptations over 20+mins. For the same reason I don’t love Zwift bike workouts either because they give precise wattage guidance for the efforts. I always just tell people to follow the intensity pattern of the workout and to know what’s coming in advance and not just follow the numbers on the screen. How are you going to learn any internal pacing strategies for racing if you’re just following the wattage on the screen and not listening to how your body is feeling at certain intensities and durations?  

So how do you know what this 9/10 RPE is? Well you should be pretty consistent in your times over the set. If there’s a big drop off it probably means you were too close to the red early on. Another good measure is that, after the last rep, you should feel like you could still do one more at the pace if pushed. Another indicator is if you don’t feel you can do the whole set of intervals and have to cut the workout short. Now, you might ask, wouldn’t I get a better adaptation, or achieve my full potential, if I ran at 100%? No pain, no gain? Perhaps, but it could only be by a small percentage if at all, and there’s many reasons I think not to go all out in training. One, it’s easier to recover if you haven’t completely smashed yourself in a workout. For endurance sports you need a large amount of volume and that would be compromised by doing your interval workouts too hard. Two, I believe there’s a psychological cost to going at your absolute max in training which you want to save for races. It takes an incredible amount of internal will to go at your true 100% and I think that most people have a hard time doing that on a weekly basis. You want to save it for a special occasion! For the reason that the difference between 90% and 100% effort is mainly psychological, it may be valuable, on rare occasions to, as Steve Magness calls it, “go to the well” in training. That is every now and again at the track, extend your effort, just to remind yourself that you can and to have something to pull on during a race (“I survived that set of 400s at the track where I was gasping for air so I can hang onto this competitor to the finish line”). Recalling all the tough work and early mornings you’ve put in can be a great motivator to push yourself that 10/10 at the end of a race.