I go for rides 3 times a week, twice with the club and once alone. Distance a week now app. 125 miles going up to 185 miles in summer. I have recently done a max test from the results it seems I need to work on my VT1. I have been told that riding around VT1 and VT2 will improve fat burn. Adding intervals will help raise V02max slightly. At what stage should I add in VT1 rides and when should I add in the intervals? Also how long should my rides at VT1 be, should they replace all my rides or should I just do one or two rides a week and for how long?