Training

HIIT: elite cardio for those with no time to lose

June 30, 20266 min read

My nights don't come with a lunch break. When the alarm sounds, either the conditioning is there or someone pays the price. HIIT — high-intensity interval training — is how I compress weeks of conditioning into 20-minute sessions. And science says it works for you too.

What it is, no fluff

Alternating near-maximal efforts (15 seconds to 4 minutes) with short recoveries. Meta-analyses show HIIT improves VO₂max — the single best predictor of cardiovascular health — in less total time than moderate steady-state cardio, with comparable benefits for body fat and insulin sensitivity.

The Lair's protocols

Level 1 — Recruit (2x/week): brisk walking or bike. 30 s hard / 90 s easy × 8. Total: ~20 min with warm-up. Level 2 — Patroller (2–3x/week): running, bike or rower. 1 min hard (8/10 effort) / 1 min easy × 10. Level 3 — Vigilante (max 2x/week): the Norwegian 4×4 — 4 min at 90% of max heart rate / 3 min active recovery × 4. Brutal and proven for VO₂max.

The rules

Warm up 5–10 minutes. Sprinting on cold muscle is an invitation to the repair bay.
HIIT is not an everyday tool. 2, at most 3 sessions a week. The rest: easy zone-2 cardio and strength. Intensity without recovery is self-destruction — I've tried it; I don't recommend it.
Real intensity. If you finish an interval able to hold a conversation, that was a stroll, not HIIT.
Impact counts. Knees complaining? Bike, rower or elliptical deliver the same cardiovascular stimulus without the hammering.

Who it's for (and who it isn't — yet)

Sedentary people, uncontrolled hypertensives and cardiac patients need medical clearance first — high intensity demands a heart that's been cleared for it. Just starting out? Build 4–6 weeks of easy aerobic base before your first sprint.

A word from the Lair: this content is informational. Get a medical evaluation before starting high-intensity exercise, especially with cardiovascular or metabolic conditions or after a long time away.

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