HIIT alternates intervals of near-maximal effort (80-100% max HR) with recovery periods. Tabata (20s work/10s rest × 8 rounds) is the most researched protocol, originally studied at 170% VO2 max. HIIT produces cardiovascular adaptations comparable to much longer steady-state training in significantly less time. Research shows 20-30 minutes of HIIT 2-3 times per week produces substantial aerobic improvements. Limitations: HIIT requires genuine high effort to be effective; most gym-goers perform 'pretend HIIT' at moderate effort that doesn’t match the research. Also: DOMS and CNS fatigue demand 48h recovery between sessions.
Key points
- Alternating maximal effort + recovery
- Tabata: 20s/10s × 8 = 4 minutes
- Matches longer steady-state training in less time
- Requires genuine near-maximal effort