Aerobic vs Anaerobic Training Effect Explained

You finish a run and your watch says "Aerobic 3.2, Anaerobic 1.4". It looks scientific, but what does it actually mean, and should you care? In short: these two numbers tell you what kind of fitness the run built, and how much.

What training effect means

Training effect is a score from 0 to 5 that shows how much a run improved your fitness, compared with what your body is used to. Most sports watches use this scale. A run that matches one normal day of your training keeps your fitness where it is; a bigger dose pushes it up.

There are two scores because running builds two different systems:

Aerobic training effectHow much the run built your endurance: your heart, lungs and the muscles' ability to use oxygen. Easy, long and steady runs raise it.

Anaerobic training effectHow much the run built your ability to run very fast for short bursts, above the pace you can hold for long. Intervals and sprints raise it.

The 0 to 5 scale

Score	Label	What it means
0 to 0.9	No benefit	Too easy or too short to change fitness.
1 to 1.9	Minor	Good for recovery.
2 to 2.9	Maintaining	Keeps your current fitness.
3 to 3.9	Improving	Makes you fitter.
4 to 4.9	Building fast	Big boost; needs good recovery.
5	Maxed out	Very hard; take extra rest.

A useful rule: a run equal to one normal day of your training scores about 2.0. Each time the dose doubles, the score goes up by about 1. That is why the same 10 km can score 3 for a beginner and 2 for an experienced runner.

How each score is worked out

Aerobic: from your heart rate

Aerobic training effect looks at your heart rate over the whole run. The longer you spend and the higher your heart rate, the bigger the dose. Windlace uses Banister's TRIMP method, the same idea behind training load, and compares it with your usual daily training on the day you ran.

Anaerobic: from running above your critical speed

Anaerobic training effect looks at how far you ran faster than your critical speed, roughly the pace you can hold for about an hour (your threshold pace). Easy runs and steady tempo runs spend almost none of their time there, so they score close to 0. Short, fast reps score high.

An old run keeps its scoreBoth scores compare the run with what your body was used to on the day you ran it. As you get fitter, new runs need more to score the same, but past runs keep the score they earned.

Which runs raise which score

Typical results. Your own scores depend on your fitness and the exact session.
Run	Aerobic	Anaerobic	Focus
Recovery jog, 30 min	1 to 2	0	Recovery
Easy run, 45 to 60 min	2 to 3	0 to 0.5	Base
Long run, 90+ min	3 to 4	0 to 1	Base
Tempo run, 20 to 30 min hard	3 to 4	0 to 1	Tempo or Threshold
Intervals, e.g. 6 × 800 m	3 to 4	2 to 4	VO2max
Sprints, e.g. 10 × 100 m	1 to 2	2 to 4	Anaerobic

Training focus

Many apps also give each run a focus: the kind of training it mostly was. In Windlace:

RecoveryVery easy running, mostly Zone 1. Helps you recover.

BaseEasy Zone 2 running. Builds your aerobic engine.

TempoComfortably hard, mostly Zone 3.

ThresholdHard but steady, mostly Zone 4. Raises your threshold pace.

VO2maxVery hard efforts, mostly Zone 5. Raises your top aerobic speed.

AnaerobicLots of fast running above threshold pace, like sprints or short fast reps.

How to balance your week

Most runs: aerobic 2 to 3, anaerobic near 0. Easy running is the base of all running fitness. Around 80% of your running should be easy.
One or two key sessions: aerobic 3 to 4. A tempo run or intervals, and a long run.
Anaerobic 2+ once a week at most, unless you are training for short races. It is hard on the body.
After a 4 or 5, plan an easy day or two. Big scores need recovery to turn into fitness.

Common mistakeChasing a 3+ on every run. Easy runs that score 2 are doing their job: they keep your base strong and let you recover for the sessions that matter.

How to see training effect in Windlace

Add your runs with heart rate, from your phone, your COROS watch or a file.
Open any run. See its aerobic and anaerobic training effect on the 0 to 5 scale, with its label.
Check its focus: Recovery, Base, Tempo, Threshold, VO2max or Anaerobic.
Look at your week. Mostly Base, with one or two harder focuses, is a balanced week.

A run's training effect (left) and its splits and zones (right).

Key takeaways

Training effect scores from 0 to 5 how much a run improved your fitness, compared with what you are used to.
Aerobic training effect = endurance, from heart rate over the whole run.
Anaerobic training effect = short, very fast running above your critical speed.
A normal day of training scores about 2; each doubling of the dose adds about 1.
Keep most runs easy (aerobic 2 to 3), with one or two harder sessions a week.

Frequently asked questions

What is a good aerobic training effect?

2 to 3 for easy runs is perfect. 3 to 4 for key sessions makes you fitter. Scores of 4 and above are big efforts that need extra recovery.

Why is my anaerobic training effect 0?

Because you did not run faster than your critical speed for long. That is normal and correct for easy runs, long runs and steady tempo runs.

Why did the same run score lower than last month?

You got fitter. The score compares the run with what your body is used to, so the same run is now a smaller dose for you.

Is a training effect of 5 bad?

Not bad, but very hard. It usually means a race or an extreme session. Take a few easy days after it.

Do I need a heart-rate monitor?

For aerobic training effect, yes, heart rate is needed. Anaerobic training effect in Windlace uses your pace against your critical speed.

See what each run didAdd your runs and Windlace scores the aerobic and anaerobic training effect and focus of every run.

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Windlace Editorial TeamGuides on training, fitness and racing from the team behind Windlace, Your AI Running App. We write in plain words and check our facts against published research.

Aerobic vs anaerobic training effect: what your run did for you