Get access to everything we publish when you sign up for Outside+.
I would be a really bad football coach, either American football or the fake type. The reason is that it’d be right before an important practice, and everyone would gather around. The athletes would be excited, ready to rock. And I’d give my rallying cry: “Everyone, let’s go out there and give a comfortable 80-percent effort today!”
We’d go on to get stomped by the opponents. But we’d be happy, and we’d still enjoy orange slices at halftime.
The problem is that with running, there is a temptation to think that practice should be very hard. For some athletes, that focus on intensity can lead to stagnation and regression due to how the body adapts over time. To put it another way: go half-assed most of the time so we can go full-assed when it counts. Let’s start by breaking down some of the physical variables at play.
To put it another way: go half-assed most of the time so we can go full-assed when it counts.
Note: these topics are too complex to review fully in an article, so I’ll be brushing over some things, but just remember that different approaches work for athletes based on backgrounds, training philosophies, genetics and goals.
Think of intensity levels on a spectrum
There is an immense body of research on the anaerobic energy system, VO2 max, critical power (or synonyms), lactate threshold, aerobic threshold, Lil Jon threshold (has yet to be reached and it is possible that the limit does not exist). In practice, the body doesn’t work in neat boxes, but across spectrums. So all of those intensity levels go into long-term growth—one level is almost never worked at the full exclusion of others because the body doesn’t often abide by on-off inflection points.
In general, the easier ends of the spectrum improve more substantially long-term. The prototypical example is Paula Radcliffe (see this 2006 study in the International Journal of Sports Science & Coaching), whose VO2 max actually decreased from when she was a champion junior athlete, but her running economy (the amount of energy she used to run fast) improved by 15 percent. That doesn’t mean she didn’t do VO2 max work—she did plenty of it. Instead, it means that the VO2 max work she did was about improving running economy by feeding back into aerobic development and more efficient biomechanical/musculoskeletal output, rather than improving VO2 max. A great running economy overview is in this 2004 review in the journal Sports Medicine.
Other studies have similar findings, with very hard workouts improving VO2 max rapidly at first, then things leveling off and even regressing. Meanwhile, aerobic development and economy can continue improving, just at a slower and steadier rate.
Other studies have similar findings, with very hard workouts improving VO2 max rapidly at first, then things leveling off and even regressing. Meanwhile, aerobic development and economy can continue improving, just at a slower and steadier rate. For example, this 2013 study in the European Journal of Applied Physiology had two groups of sedentary women perform three training sessions a week, with one group doing high-intensity intervals and the other doing lower-intensity intervals. The improvement for both groups over 12 weeks was similar, but 60 percent of the progress in the high-intensity group happened in the first three weeks, compared to just 20 percent for the lower-intensity group. Chart that out long-term, and it’s likely the low-intensity group would continue progressing, particularly with periodic harder efforts mixed in.
A primary focus on very intense training can actually curtail some aerobic development—that’s a founding principle of developing base and periodization. Much of the cause comes down to aerobic enzyme activity, lipid oxidation/metabolic factors and mitochondria biogenesis. I have been told that mitochondria are the powerhouses of the cell, so they have the same role in the cell that Lil Jon has in the club.
In addition, training intensity affects muscle fibers, with more intense intervals calling on more fast-twitch and intermediate fibers, particularly for shorter efforts. In moderation, that’s OK, but go too hard too often and it may actually change the way intermediate muscle fibers behave (though a debated topic), as outlined in this 2016 article in the Journal of Strength and Conditioning Research. That’s part of the reason why Coach Tom Schwartz focuses heavily on “critical velocity” intervals, around 90 percent of VO2 max, or an effort athletes could hold for 30-plus minutes. Or take a peek at Eliud Kipchoge’s rumored training log, which involved lots of shorter intervals around one-hour effort or easier.
That’s why high-intensity interval training often makes for tough, strong, inefficient athletes
Train at the intense end of the spectrum too often, and not only do low-level adaptations risk wasting away, the top-end can also stagnate after you get to races around a mile and beyond. That’s because the dominant input of all of these efforts is aerobic. The reason it’s called base is that it’s always going to make up a massive portion of performance potential in endurance events, even ones that feel all out when you’re doing them.
Train at the intense end of the spectrum too often, and not only do low-level adaptations risk wasting away, the top-end can also stagnate after you get to races around a mile and beyond.
You can see that principle at work in the training of Olympians, where 800/1500-meter runners may sometimes be very low volume. But most of a training cycle for 5K runners doesn’t look that much different than the marathon, particularly as athletes age past VO2 max peak potential (which happens younger than you’d think).
And therein lies a lot of the problem. What is rewarded when you’re very young or just starting out is much different than what is rewarded after those initial gains are achieved or over long time horizons. Since potential unveils itself over many years, that can create difficult associations. “Why isn’t this working like it used to?! Why am I so tired all the time?” Meanwhile, it’s working the same way, but you can only go so far down that path before the trail starts to get overgrown.
Anecdotally, this principle seems to be especially important for athletes as they begin to explore their ultimate potential and are able to achieve very high outputs. At first, all workouts may feel hard since there is less room to work with at the upper end of the spectrum. But very developed athletes could do astonishing workouts each week, which can come with astonishing risk as well. Basically, you probably need to be more careful about where you point a bazooka than an air gun, though you should practice care with both.
Long-term growth is all about aerobic development feeding back into running-economy development, which happens best when athletes feel good
The temptation is to have killer workouts, providing Strava followers with some GPS porn. But going all-out risks chipping away at the aerobic walls that are building over years and decades. In moderation, that’s fine. It’s all very complicated and you will not reach your peak potential if you don’t occasionally go very hard.
However, if you go to the well too much, you’ll go back and find that the water is all gone. Or maybe the girl from The Ring will be staring back at you.
Health also plays a role
Most importantly, going really hard risks musculoskeletal injury and overreaching (excess fatigue and biomarker changes) and overtraining (endocrine disruption and nervous system issues). Adaptation happens when the body is on track physically. Some athletes are dealing with a genetic context that lets them push to the edge consistently without long-term risk. For most athletes, though, the sweet spot happens when training doesn’t take too much out of their souls too often (and when it does, it’s followed by plenty of recovery). Throw a dozen eggs at the wall, and one might not break, but that doesn’t mean the other 11 eggs just aren’t trying hard enough.
For most athletes, though, the sweet spot happens when training doesn’t take too much out of their souls too often (and when it does, it’s followed by plenty of recovery). Throw a dozen eggs at the wall, and one might not break, but that doesn’t mean the other 11 eggs just aren’t trying hard enough.
My favorite study on this subject was published in Physiological Reports in 2016. In a high-altitude training camp, the German national team put athletes on a strict load-management program by measuring numerous biomarkers. If markers were off, training was reduced. The athletes improved and there were no signs of underperformance, chronic muscle damage or activated inflammatory processes. We can’t do that in our own training (though we can do blood tests with Inside Tracker or other services), but we can try to use similar principles related to perceived effort and fatigue to support long-term growth.
Most efforts are relaxed so you can get out there the next day and the next week without causing a crapstorm on a cellular level, which might not always be perceptible in the moment unless you’re doing constant biomarker monitoring. And when you do push those absolute limits, the body can adapt because it’s not already trying to recover from a past effort that caused excessive breakdown. The cellular-level impacts of very-hard efforts can have long tails, so, even when your body and muscles feel ready, disaster may already be brewing.
And psychological sustainability may be the most key element of all
Training long-term is all about stacking build-up stresses, and limiting break-down stresses to when you can use them purposefully and joyfully. A proxy for that is often whether you dread harder efforts. If you do (and you don’t hate running altogether), there’s a good chance your body is just doing too much work for where you are at in that moment.
Most workouts should feel like a kid at recess. Yes, you push. But no, you don’t push until they have to scrape you off the blacktop with a spatula.
Most workouts should feel like a kid at recess. Yes, you push. But no, you don’t push until they have to scrape you off the blacktop with a spatula. I like athletes to think of five bullet-points for most workouts:
-You should not have to fade substantially within individual intervals or over the course of a workout unless that’s intentional. And don’t race tempo runs unless that’s the goal of the workout.
-You should rarely go faster than the pace you’d run for a mile/3K except in shorter strides, with the strides being key to speed development. An exception to these rules is when you’re training for specific paces of very fast races on the track or roads (or shorter mountain races that are extremely intense).
-When in doubt, slow down intervals and push more at the end of workouts rather than going too hard at first. It’s often fine to push at the end as long as you’re not emptying the tank the whole time.
-Every 2-6 weeks in more focused training (depending on individual physiology and background), it’s OK to go fully to the well, just recover plenty. See this article on four of the biggest workouts I give athletes for some of the justifications for why.
-Try not to interpolate from outliers. Some athletes can crush hard workouts seemingly every day, and that is probably related to genetics and background rather than a principle that applies generally
To put it all together, imagine this workout in your training plan: 6 x 3 minutes fast with two minutes easy recovery. Some athletes could do that type of workout around 10-minute race pace or even faster. That could undercut growth, especially if done on multiple workouts. Unless it’s related to specific training goals, it would probably be best at 30-minute race pace or easier with a slight progression of effort, possibly with faster strides after. The same applies to tempo runs not being little races.
There’s a ton more that could be said on this topic. You ever been to a dump and seen all the individual pieces of trash thrown into the pile? Imagine each one of those is a caveat or a complication, and that’s what my brain looks like all the time.
But for most athletes thinking about doing consistent workouts, all that really matters is this basic principle. Try not to celebrate pain or going to failure as a proxy for growth, because growth happens sustainably when you feel good.
Now let’s go out there and give 80 percent today.
Small Business Shout Out
This one is near and dear to my heart. Back in 2015, Trail Runner magazine took a chance on letting me write an article. I owe them so much for taking that chance and continually taking chances almost every week since. While it feels like a big operation, the editorial staff is just a few amazing people.
With ad buys at an all-time low across media, now would be a great time to get a magazine subscription for yourself and friends. That support could help Trail Runner stay alive in this crazy time. If you like these free articles they let me write, a subscription to the print issue would be incredibly helpful even if you just skim through for photos. Subscribe for a year for $29.95 or 2 years for $44.95 at the link here.
David Roche partners with runners of all abilities through his coaching service, Some Work, All Play. His book, The Happy Runner, is about moving toward unconditional self-acceptance in a running life, and it’s available now on Amazon.