Engine Builder · Block 1
The base your engine's been missing.
What it's for
- You have decent strength but get gassed 15 min into a metcon.
- 5 km feels harder than it should — HR runs away at moderate pace.
- You want a plan that builds the base, not just chases intervals.
- You'll swap rowing / cycling / ski-erg / running as your machine.
The arc
Eight weeks of Zone 1/2 base with a single weekly hard session added in week 4. Norwegian 4×4 intervals appear once you can hold Z2 for 45 minutes without HR drift. Retest week 8 measures submax-HR at your intake pace — the aerobic gain is real and readable.
What gets retested
Week 8: submax HR at your intake pace should be 3-8 bpm lower. Resting HR drops 3-10 bpm.
Honest outcome ranges
Ranges are honest, not guarantees. Response varies — HERITAGE non-response distributions apply to any structured training program.
What it cites
Hickson 1980 · concurrent training
The load-bearing concurrent-training result — interference is proportional to endurance volume.
Helgerud 2007 · Norwegian 4×4
The single most efficient protocol for raising VO2max in trained-not-elite athletes.
Seiler 2010 · polarised training
80/20 easy/hard is the honest volume distribution — this program follows it.
Not for you if
- Unmanaged high blood pressure (resting > 160/100).
- Exertional syncope or unexplained dizziness — stop and see a clinician.
- Recent post-COVID: return-to-exercise gate, not this program.
- Any flaring joint or tendon condition — resolve first.
Sign up on the app, complete the intake, and your first session is on Today within two minutes. Free during beta.