Like others I'm an office working sitting at a computer most of the day. Riding my mountain bike is my main source of activity during the work week. I work from home and I can escape during lunch for an hour, or alternatively after work for an hour. On average I ride 4 times a week for about 5-6 hours of activity. I haven't really ridden with any sort of plan I normally just go out and ride. 1-2 of those rides will be with my 12yo son so on those rides I barely push into zone 3. I don't really want to leave him in the dust so riding hard on those rides isn't an option. The other rides by myself are mainly for fitness. The question is, how to I make the most out of my limited riding time. As I said 1-2 of my 4 rides a week that are slow zone 2-3 for about 60-90 minutes. Should I be looking for higher intensity in my other rides? My "Hard" rides according to my watch I will be in Zone 4 bout 50% of the time (141-157bpm), zone 5 about 10-20% (158-175bpm), and the rest Zone 1-2-3. Should I be looking at getting more time in Zone 5? Adding an extra 30 minutes per ride for longer durations in Zone 4? Or even longer Zone 2 rides? If I had an ultimate goal it would be to be able to give hard effort for longer periods of time. On a 2 hour ride with really strong riders who routinely race I can mostly keep up for about 45-60 minutes then I start losing my legs and start falling back especially on any big pedally parts.