Review of Building the CrossFit Engine: Energy Systems Without Guesswork

Coach’s Brief
If every session feels like a race, you’re under-developed aerobically. If every session is easy pootling, you’ve no top gear. The CrossFit engine needs all gears—Zone 2 economy, threshold grit, VO₂ pop—layered across mixed modalities.

Know Your Gears (Plain English)

Zone 2 (endurance): Conversational effort; builds mitochondrial density and recovery capacity.

Threshold (lactate turnpoint): “Comfortably awful”; sustainable for ~30–60 minutes.

VO₂ (high power): Hard 1–4 minute repeats; improves max aerobic power.

Alactic (power): <15-second bursts; sharpens start/finish kick and barbell speed.

Why CrossFitters Need Zone 2
It’s the base that lets you recover between sets, rounds and training days. It also improves fat utilisation and caps the heart-rate drift that ruins long chippers. Two Zone-2 sessions a week (30–45 minutes, bike/row/run, nose breathing if possible) go a long way.

Sample Week (Everyday Athlete)

Mon – Threshold mixed: 3 × 8 minutes: 12/10 cal row, 12 wall balls, 12 toes-to-bar. Rest 2 minutes. Aim even pacing.

Wed – Zone 2: 40 minutes easy bike/row, nasal breathing, HR in Zone 2 (talk test: full sentences).

Fri – VO₂ on machines: 6 × 2 minutes hard / 2 minutes easy (alternate ski/bike). Keep all hard intervals within 5% wattage.

Sat – Long mixed aerobic: 30–40 minutes continuous: 400 m run, 20 KB swings (light), 15 box step-ups, 12 push-ups.

Pacing Anchors

Row: Track 10-minute sustainable split. VO₂ sets at ~5–10 seconds faster; threshold at ~2–5 faster.

Bike: Know your 10-minute calories/hour or watts; cap VO₂ at +10–15%.

Run: Use RPE and talk test; or your 10 km pace for threshold anchors.

Common Engine Errors

Grey-zone addiction: Everything at medium-hard, nothing truly easy or truly hard.

Monostructural only: Great on the bike, dies when toes-to-bar appear. Build mixed-modal endurance.

No repeatability: First interval is a PB; the sixth is a collapse.

Ignoring breathing mechanics: Mouth-only gasping = lost cadence and sloppier movement.

Coach’s Fixes

Keep easy easy. If you can’t speak in phrases, you’ve wandered out of Zone 2.

Use repeatability as KPI. Intervals should stay within 3–5% across the set.

Include cyclical + gymnastics combos at threshold to harden grip/midline under breathing load.

Practise nasal or cadence-timed breathing on easier pieces to tidy mechanics.

Verdict
A serious engine is built, not wished into existence. Layer Zone 2 for economy, threshold for grit, VO₂ for top-end, and fold it into mixed pieces. Pace by metrics, not hope, and you’ll stop dying on minute six.

-Luke