How to find your real max HR: The formula 220 − age is a useful estimate, but individual max HR varies significantly. For a more accurate number, do a field test: after a thorough warm-up, run 3 × 1 km at increasing effort, then sprint the last 400m all-out. Your peak HR reading is close to your true max.

Why zones matter: Running in the right zone means the right training stimulus. Most runners run their easy days too hard, which accumulates fatigue without extra fitness benefit. Z2 is your aerobic engine — protect it.