Estimate maximal oxygen uptake (VO2 max) — the gold standard of cardiorespiratory fitness.
VO2 max measures the maximum amount of oxygen your body can use during intense exercise, expressed as mL O₂ per kg body weight per minute. It is the single best predictor of all-cause mortality — better than smoking, hypertension, or diabetes. Each 1 MET (3.5 mL/kg/min) improvement reduces mortality risk by ~12%.
| Age | Men Excellent | Women Excellent |
|---|---|---|
| 20-29 | >52 | >42 |
| 30-39 | >49 | >38 |
| 40-49 | >45 | >35 |
| 50-59 | >41 | >32 |
| 60+ | >37 | >29 |
Norwegian 4×4 HIIT (4 min hard, 3 min easy, repeated 4×) consistently produces the largest gains, typically 10–25% improvement in 8 weeks. Long zone-2 endurance work also raises VO2 max while building aerobic base.