For people who do 2x20' builds, if I break that up into say 5x8' does it give similar work? Is it just about time in that zone overall from that workout to get a benefit? I ask this because I live in a very limited area for riding during the week. I can usually get two 8 minute hits in a loop with a couple two minute relaxations between due to the route. Is this ok or should I be looking at something else?