Not sure how accurate watch-based VO2 Max really is, but before getting the Hydrow, it said my VO2 Max was 38.5, giving me a "fitness age" of 42. I'm 40. After using
Suunto 9 - Features - Fitness level
Suunto 9 gets Firstbeat
Suunto 9 Peak smartwatch review: big on style, not so hot on substance | T3
Fitness level... I'm 32 : r/Suunto
Software update available for Suunto 9
Suunto 9 Series Gets New Sleep & Fitness Metrics from FirstBeat | DC Rainmaker