By RunDoyen.
Featuring coaching insights from Jeff Messer.
Adapted from a RunDoyen coach conversation and edited for clarity.
TL;DR
- Your training works when it creates specific adaptations to the stress you apply, so every run should have a clear purpose.
- Aerobic development is not just “more miles.” It includes changes like expanded blood volume, improved oxygen delivery, more capillaries, and more mitochondria in working muscles.
- Anaerobic work can support endurance performance, including late-race surges and possibly improving mitochondrial quality through short sprint interval training.
- VO2max sessions target speeds near maximal aerobic capacity, but the best format depends on your training age and durability.
- Threshold training (tempo and progression runs) builds a higher sustainable pace without turning every session into a race.
If you want help translating these concepts into a week-by-week plan that fits your goals, you can get matched to a RunDoyen coach.
Table of Contents
- Why “purpose” matters in endurance training
- Aerobic training: what it is and what it changes
- Anaerobic training for distance runners: where it fits
- VO2max work: what it targets and how to use it
- Threshold training: tempo runs and progression runs
- Running economy: getting more speed from the same effort
- Putting it together: a simple “purpose-first” framework
- Common mistakes
- Safety and when to get help
Why “purpose” matters in endurance training
Most runners do not need more hype. They need more clarity.
When you understand what a workout is trying to change in your body, you are less likely to:
- go too hard on an easy day
- turn threshold into a time trial
- chase paces that do not match today’s fatigue, weather, or terrain
- stack stress in a way that quietly breaks you down
A useful coaching lens here is the idea of specific adaptation to imposed demand. In plain terms: your body adapts to what you repeatedly ask it to do. That is why two runners can log similar mileage and end up with very different results, one runner’s “easy” is truly easy, while the other runner’s “easy” is a disguised tempo run.
Purpose-first training is not about memorizing jargon. It is about aligning effort with outcome.
Aerobic training: what it is and what it changes
Aerobic training is sustained, rhythmic, large-muscle activity that can be maintained continuously for extended periods. For runners, that is most often your easy runs, steady runs, and long runs.
From a physiology standpoint, aerobic training matters because it improves the chain of events that lets you:
- deliver oxygen to working muscles, and
- use that oxygen to create energy for sustained running
Here are several classic endurance adaptations that help explain why easy and long running are so powerful.
Expanded blood (plasma) volume
One early endurance adaptation is an expansion in plasma volume. More circulating volume sets the stage for better oxygen transport capacity, including the potential for more red blood cells and hemoglobin over time. The practical takeaway is simple: aerobic training can improve how effectively your body moves oxygen where it needs to go.
More capillaries around working muscles
Capillaries are the tiny blood vessels that interface with muscle tissue. Increasing capillary supply and density improves the ability to move oxygen from the bloodstream into muscle. For endurance runners, that supports longer, steadier energy production when the pace is controlled and continuous.
More mitochondria in skeletal muscle
Mitochondria are structures inside muscle cells that use oxygen to produce energy. Aerobic training is a strong stimulus for increasing mitochondrial content, especially in the muscles doing most of the work. In practice, “more mitochondria” contributes to running longer or running the same pace with less strain.
General guidance: Aerobic development is usually best built with consistency first, then gradual volume and stress progressions. If you want a structured build that matches a specific race distance, a plan like the Calculated Marathon Training Plans reflects this layered approach.
Anaerobic training for distance runners: where it fits
Anaerobic energy production refers to producing energy without directly using oxygen in the immediate process. In racing terms, very short, very hard efforts rely heavily on anaerobic contribution.
So why should an endurance runner care?
Reason 1: the late-race surge
In many races, performance is decided late, not early. The final stretch of a 5K, 10K, or even longer events often includes a decisive change in pace. That “kick” demands higher anaerobic contribution. A runner who only trains steady can feel smooth early and stuck late.
Reason 2: sprint interval training and “mitochondrial quality”
A more nuanced point is that very short sprint interval work may contribute to mitochondrial quality, not just quantity. Endurance training is a well-known stimulus for increasing mitochondrial amount, but short sprint interval training has been discussed as a possible way to improve how well those mitochondria function.
This is not permission to turn every week into a suffer-fest. It is a reminder that small doses of speed can serve endurance goals, if they are placed wisely and recovered from fully.
VO2max work: what it targets and how to use it
VO2max work generally refers to training at speeds near your maximal aerobic capacity. Done well, it can support your ability to sustain faster paces aerobically.
What VO2max sessions can look like
VO2max training can span a wide range, depending on the athlete:
- Short repeats, such as 200m repetitions, used in a measured way to accumulate quality without overwhelming fatigue
- More demanding repeats such as 800m to 1600m (development dependent) to apply a stronger stimulus
A key point is that the “right” VO2max format depends on how durable and aerobically developed you are. The more advanced the runner, the more they may tolerate (and sometimes need) longer, more demanding intervals.
How to estimate VO2max pace without a lab
Many runners will never do lab testing, and that is fine.
A practical estimate discussed in coaching circles is that VO2max speed may be roughly around:
- mile race pace for more developed/advanced runners
- closer to two-mile/3K effort for younger or less developed runners
It is still an estimate. Conditions, fatigue, terrain, and training age all matter.
General guidance: If you are unsure, use feel as a governor. VO2max work is hard, but it is not a sprint. If your mechanics are falling apart or you cannot recover enough to repeat quality, you are likely overreaching.
For help sanity-checking training paces across run types, the Running Pace Calculator can be a helpful reference point.
Threshold training: tempo runs and progression runs
Threshold training is one of the most useful bridges between easy aerobic work and high-intensity intervals. It complements easy running by raising the pace you can sustain without tipping into full-on anaerobic struggle.
Tempo runs: “comfortably hard”
A classic tempo run is a sustained effort, often around 20 minutes, at a pace best described as “comfortably hard.” It should demand focus, but it should not empty the tank.
If you finish a tempo run and feel like you just raced, it was probably not a tempo run.
Progression runs: a gentle step faster
A progression run layers in pacing discipline. One example:
- start the first 10 minutes at a comfortably hard, controlled effort
- run the final 8–10 minutes slightly faster (on the order of 5–10 seconds per mile)
The value here is not just physiology. It is learning control under fatigue.
Progression should be cautious
A practical progression example is moving from 20 minutes at 6:00/mile to about 5:56/mile, which is roughly a 1% shift. That can sound small, but over time those measured changes stack into meaningful fitness.
If you want more clarity on how tempo and threshold language can differ (and why it sometimes gets confusing), see Tempo Run vs Threshold Run.
Running economy: getting more speed from the same effort
Running economy is often treated like a buzzword, but it is a big deal: it reflects how much energy you use to run at a given pace. Two runners can share the same aerobic capacity and threshold, yet the more economical runner often performs better because they spend less energy holding race pace.
Two practical ways to improve running economy
Two training tools highlighted in coaching practice and athlete development are:
- Plyometric training (non-running)
This can improve the spring-like qualities of tissues and the coordination of force application. - Short hill sprints (running-specific)
An example format is short, hard hill sprints of roughly 8–12 seconds, with full walk-back recovery. The goal is power and posture, not exhaustion.
If you want to explore hill session options and how they fit into broader training, Hill Training for Runners is a useful companion resource.
A note on cadence and the “magic number” trap
Some runners fixate on a single cadence target. While cadence can relate to efficiency, there is meaningful individual variability. Rather than forcing a number, focus on training that improves your mechanics, strength, and efficiency over time. Economy is a result, not a hack.
Putting it together: a simple “purpose-first” framework
The goal is not to cram every training type into every week. The goal is to layer the right stress, at the right time, at the right dose, so you can adapt and stay healthy.
Workout Purpose Cheat Sheet
| Run type | What it should feel like | Primary purpose | Example session |
| Easy run | Conversational, relaxed | Aerobic base, recovery support | 30–60 minutes easy |
| Long run | Steady, controlled | Endurance, durability | 75–150 minutes easy-steady |
| Tempo run | “Comfortably hard” | Raise sustainable pace | 20 minutes steady tempo |
| Progression run | Controlled, slightly faster late | Pacing skill + threshold support | 10 min steady, 10 min slightly quicker |
| VO2max intervals | Hard but repeatable | Improve maximal aerobic capacity | 6–10 × 400–800m (development dependent) |
| Short hill sprints | Powerful, crisp | Running economy support | 6–10 × 8–12 sec hills, walk back |
A weekly “minimum effective” structure
Here is a simple way to think about balance:
- Most mileage stays easy enough to recover from
- 1 day targets threshold (tempo or progression)
- 1 day targets VO2max or controlled speed, depending on the phase
- Long run anchors the week
- Small doses of hills or strides can support economy without dominating the program
General guidance: Your best week is the one you can repeat, not the one that looks heroic on paper. Consistency and musculoskeletal health are performance multipliers.
Common mistakes
- Turning easy runs into steady runs because the pace “feels too slow.”
- Treating tempo runs like races, then needing extra recovery that derails the week.
- Chasing precise paces while ignoring terrain, heat, wind, or accumulated fatigue.
- Doing anaerobic work without full recovery, turning “speed” into sloppy grinding.
- Progressing too aggressively, instead of making small (often 1%) changes that compound.
- Trying to “fix” cadence with constant monitoring instead of improving economy through training.
Safety and when to get help
Training should challenge you, but it should not routinely break you down.
Consider dialing back and getting qualified help if you notice:
- sharp or worsening pain that changes your stride
- repeated swelling, numbness, or instability
- fatigue that keeps escalating for multiple weeks
- persistent inability to hit reasonable effort targets despite normal sleep and nutrition
- signs you are not recovering between sessions (resting heart rate, mood, soreness, performance all trending the wrong way)
If you are returning from time off or uncertainty, prioritize conservative progressions and sustainable consistency over intensity.
Closing
Exercise physiology does not have to be intimidating. You do not need a lab test to train intelligently. When you understand the purpose of aerobic work, threshold training, VO2max sessions, anaerobic touches, and economy-focused drills, you stop guessing and start building.
If you would like to compare coaching styles and find the right fit for your goals, you can browse RunDoyen coaches.
FAQ
1) What is the most important adaptation from aerobic training?
Expanded oxygen delivery and utilization capacity, including changes like increased plasma volume, capillary support, and more mitochondrial content in working muscles.
2) Do distance runners really need anaerobic training?
It can help, especially for late-race pace changes and short finishes. Small doses placed well can complement endurance development.
3) What is a tempo run supposed to feel like?
“Comfortably hard,” steady, and controlled. You should finish feeling worked, not wrecked.
4) How do I estimate VO2max pace without lab testing?
Many coaches approximate it near mile race pace for advanced runners and closer to 3K/2-mile effort for developing runners. Use repeatability and form as guardrails.
5) What improves running economy the most?
Training that improves efficient force application, such as short hill sprints and appropriate plyometric work. Consistent aerobic training supports it too.
6) Is 180 steps per minute the “perfect” cadence?
Not necessarily. Cadence varies by height, speed, and mechanics. Focus on becoming more efficient through training rather than forcing a single number.
7) How can an online running coach help with these concepts?
An online running coach can place the right workouts in the right order, progress them cautiously, and adjust based on recovery, durability, and real-world constraints so you adapt without accumulating chronic fatigue.
