997cc047_ng_Zones___Guide___Wattbike_UK__Physiological_Adaptations
[Training Zone] Zone 2 [Purpose] Improve efficiency [Race fitness] Able to produce more power with the same level of effort, works on technique/skill [Physiological Adaptations] 
Improves the ability to use oxygen, produce power and increases efficiency
Heart Rate and Power Training Zones - Guide - Wattbike UK
Physiological Adaptations