TriPeak

Aerobic base training

Build the engine first. Speed is what you do to it later.

How the week is distributed

A aerobic base week puts roughly 88% of training time easy, 10% moderate and 2% hard. The percentages are of time, not of sessions — which is why a week with two hard sessions in it can still be 88% easy.

Easy

88% of weekly training time

Moderate

10%

Hard

2%

How it plans

• Spend long blocks — months, not weeks — almost entirely aerobic, building duration before touching intensity.
• Cap easy sessions by heart rate or feel and hold the cap even when it feels absurdly slow.
• Add intensity only once volume has plateaued and the easy pace at a given heart rate has stopped improving.
• Prioritise consistency and frequency over any individual session.
• Strength and technique work belongs in this phase, where it costs nothing.

Why it is meant to work

The claim is that the slow adaptations are the ones that matter most and take longest: capillary density, mitochondrial content, the heart's stroke volume, the body's willingness to burn fat rather than glycogen. These respond to duration and frequency far more than to intensity, and they take months rather than weeks.

Intensity, on the other hand, is argued to be quick to gain and quick to lose — a sharpening applied to a base, not a substitute for one. Adding it early is held to interfere with the aerobic work by adding fatigue that shortens the easy sessions.

The enforcement mechanism is a cap: a heart rate or an effort that easy sessions must stay under, held even when it feels absurdly slow. The discipline of the cap is the method, and it is the part people abandon.

Who it suits, and how it fails

Suits

Athletes returning from a break, new to endurance sport, coming back from injury, or with a long runway to a late-season race.

Watch out for

Slow to show results and easy to abandon in week five. Held too long it leaves an athlete aerobically strong and unable to go fast — the base has to be built on eventually.

Strength of evidence

The oldest of these approaches and the least formally tested, since nobody runs a controlled trial over two years. Consistent with what is known about mitochondrial and capillary adaptation to prolonged low-intensity work.

The research behind it

Every citation below was checked rather than remembered, and each note says what the study found and what it does not establish.

1. Casado et al. (2022), Sports Medicine – Open 8:46Relevant for the volume finding rather than the periodisation: world-class distance runners accumulate substantially more total volume than slower highly trained runners. Consistent with the base argument without testing it.
2. Seiler & Kjerland (2006), Scandinavian Journal of Medicine & Science in Sports 16(1):49–56Cited here for the same observation read differently: the overwhelming majority of elite training time is easy. Whether that is a base being built or a distribution being maintained is exactly what the evidence cannot settle.
3. No long-run controlled trial existsThis is the honest state of it. Nobody has randomised athletes to two years of contrasting base policy, and nobody is going to. The approach rests on physiological plausibility and a century of coaching practice, which is weaker than it sounds and stronger than nothing.