997cc047_ng_Zones___Guide___Wattbike_UK__Physiological_Adaptations
[Training Zone] Zone 3 [Purpose] Improve sustainable power [Race fitness] Improved sustainable power, good for all cycling events [Physiological Adaptations] 
Improves carbohydrate metabolism, changes some fast twitch muscle to slow-twitch
Heart Rate and Power Training Zones - Guide - Wattbike UK
Physiological Adaptations