If I say the word 'speedwork,' what comes to mind? If you're a marathoner, it might be Yasso 800's or 1km, maybe even mile repeats. An ultra runner might think of long moderate uphill repeats. I have had other runners tell me 'my last coach just assigned tempo runs as 'speedwork.'
The problem of course, is that for many athletes... these things may not actually be helping much - at least, not helping speed!
At least in part, this isn't strictly a difference in philosophy, or even people incorrect about the science, but rather just the ignoring of a really simple but crucial point.
Because time and effort determine adaptations, the distance required for intervals varies by your fitness level. Distance-based intervals will not be the same for you as another athlete.
Let's use Yasso 800's as a popular example of 'speedwork' in a marathon training plan. I have heard athletes say that this is the only speedwork they've done in years of marathon training.
First of all, that's a common sign of trying to be too much of a 'specialist' – something that's not good for your long-term development, and a point you can read more about in this article. More importantly for this discussion, for a 3:30 marathoner that might mean years spent doing 3.5min intervals with 3.5min recoveries... and that's it.
However for our current discussion, what matters is this: the efficacy of speedwork comes down to effort over time. You cannot simply take training made for a certain athlete and adjust the speed and volume. It will not work for you, because distance is totally irrelevant.
Think Time Instead of Distance
This is the most vital component. Time and effort is what we are interested in when designing, discussing and executing training. Distance and pace are outputs that have little-to-no bearing on the potential adaptations from a workout. In particular, discussing time and effort are what makes workouts and information universal across different athletes, fitness levels, weather and surfaces.
While you can certainly convert durations back to distances for your own purposes, I'd recommend trying out time-based intervals. By doing workouts by time, you can do your workouts anywhere, you're not subject to the whims and errors of a GPS watch, and your workout will always be the right stimulus even if you're at altitude, it's hot, you're on a rail trail, etc.
I have also seen significant benefits and even big breakthroughs from nearly everyone who has decided to ditch pace and run by feel for most/all of their runs. We know it works – are you next?
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The Science of Interval Duration
In order to truly work on your speed and running economy, intervals need to be short and fast. Not longer and moderate. Philosophies differ and there are many ways to make this work, particularly for elite/professional athletes. In extreme cases, say with professional track athletes specializing in distances under 5000m, things may look quite different. But for the vast majority of athletes, this is a good starting point to begin thinking about interval training.
For most athletes I work with, I consider intervals between 1min and 4min to be working on speed and VO2max, and intervals longer than 4min to be working on critical velocity or lactate threshold. This is a simplification of course – there is overlap in adaptations to a given workout, and different things can work for different athletes at different times.
Some people divide up speedwork further into 'intervals' which work primarily at VO2Max and 'repetitions,' which are a bit faster. Personally, I think the words are similar enough to be ambigous, so I simplify the language into 'speedwork' and instead give individualized suggestions for each and every workout to my athletes.
This will all vary by the overall experience level of the athlete, particularly if they've spent years developing their overall speed and athleticism. It also depends on their overall goals. High-level, experienced athletes might do VO2max workouts with intervals as long as 5 minutes. Less-experienced athletes often do many more 1-3min intervals. Aerobically-limited athletes will do different training than biomechanically-limited athletes.
The crucial part is that there is variety in interval length and recovery ratio, and that athletes progress from shorter intervals to longer ones as they gain strength, fitness and experience. Athletes should not run the same length of interval for every workout!
What's all this mean for our Yasso 800's example?
For those that aren't familiar, Yasso 800's is a workout named after Bart Yasso that consists of gradually building up over the course of marathon training to 10x800 meter repeats, with equal time recoveries.
The idea is that if you can run those 800m repeats in the same number of minutes:seconds as your hours:minutes marathon goal, then you have the fitness to run that time at your race. That of course assumes overall proper training including long runs, proper fueling and more.
For someone who is running slower than a 4:00 marathon, Yasso 800's really aren't speedwork. Even for a 3:00 marathoner, if that's the only speedwork they do, it's holding them back.
So if you're a 4-hour marathoner, those 800m repeats turn into 4min fast (more likely moderate) and 4min easy. Not as beneficial for working on your speed, particularly if that's all you do! By contrast, a 2:20 marathoner is running them in 2.2min, with 2.2min easy between. That's a totally different workout for that athlete, with a different intent and different adaptations! As you can see, you cannot simply copy distance-based workouts across athletes.
That's not to say that Yasso 800's are useless; they may have utility for some athletes, or as a 'fitness test' periodically during training (though I have other concerns around those). But if that's the majority of speedwork that you're doing, you're just holding yourself back!
Intervals vs. Recoveries
Taking a deep dive into work and recovery ratios and interval length is beyond the scope of this article, but here are a few points to keep in mind.
First, the shorter the work interval, the shorter your recovery should generally be, at least for VO2Max work. The longer the work interval, the longer the recovery. In particular, your body takes time to build to VO2Max. That means the recoveries for shorter intervals should be partial so that you reach VO2Max sooner with each interval. That might mean 2min intervals with 90sec or even 1min recoveries. For workouts faster than VO2Max, recoveries should be longer so that you fully recover.
Next, not all intervals within a session need to be the same length. Ladder workouts, shortening intervals over the session, keeping work intervals the same but shortening recoveries... there are so many ways to make workouts interesting and elicit adaptations! . While there are some guidelines to ensure you get the adaptations you're after, there's a ton of freedom in here.
Don't Just Copy the Elites
Now this concept of time vs. distance when comparing across athletes is a great example of something that I think is far too prevalent among runners, and that is copying training of elite and professional athletes. There is a lot of cause for concern there, and I believe it's one of the top causes of injury among runners.
Correlation vs. Causation
Correlation vs. causation is something that is crucial to think about when analyzing the training of high-level runners. Is the training Eliud Kipchoge is currently doing the reason why he's going to run 2:0x at his next marathon? No, it's not. That training might be the reason why he can maintain, sharpen and even gain a little more fitness or competitive edge. But the reason he is fast and fit is becuase of his fitness growth over many years.
Elite runners aren't fit because they run the workouts/volume they do, rather they run the workouts/volume they do because they're already fit, and that level of training is the only way they can continue to adapt.
An extremely simple example is weekly volume (overall quantity of miles or time). It's easy to think that high volume runners are really fit becuase they run a lot of miles. While thats true in the sense of life-time miles, in reality, they are running a lot of miles right now because they're really fit. Their body no longer adapts at lower mileage levels – they have to run high volume in order to continue improving.
That's not to say you shouldn't think about your running volume when evaluating your training, but if you are making progress at the level you're at, adding more volume probably won't cause your body to adapt faster, and is more likely to lead to injury. Conversely, if you have reached a plateau in your improvement, and are doing everything else right in training, remaining injury-free, then bumping the volume up a bit may be the right decision!
Intent and Context Matter
As I mentioned in the section about interval duration, using a workout designed for another athlete is a potential problem. Something I see a lot is "Kipchoge did this workout as part of a 130mi week. I am slower and run lower volume, so I'm going to do the same workout and adjust the pace and number of reps." Don't do it! You're now doing an entirely different, and potentially useless workout. You've taken away the entire reason that worked for Kipchoge. You've ignored the intent of the workout and focused on the result.
Now, I'm not suggesting that we can't look at what is working for elites and learn from it, but we can't just copy it and adjust the pace and volume. We need to look at what the intent of the workout was. Remember, workouts aren't just 'do hard work = get faster,' we're talking about specific physiololgical processes! Just as importantly, we need to know what kind of training was done before and what the plan is for after. No workout, or week of runs happens in a vacuum – so the context is crucial to understanding and replicating the effects of the workout.
I highly recommend reading this article about why training plans are generally ineffective, and how to improve them.
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