Project Zone 2: Day 18 🫀 First day adding intervals into the mix 🧪 Tried the Norwegian 4×4 VO₂ max method - four sets of 4 min at 85–95% of max HR. (My max is 206, tested). Definitely a shock to the system but felt good to push a different gear for the first time in a while. Back to Z2 next time. #zone2training #zone2 #runningtok #runner #projectzone2