This workout is a great way to build the aerobic engine. The fitness acquired from this sort of a workout will give you great staying power in difficult ride or race situations and this will also increase your lactate threshold. Your total ride time should be between 1.5 hours and 4 hours with your zone 3/Tempo effort/efforts being as short as 20 minutes and as long as 1.5 hours. If you are just doing this for the first time try a 1.5 hour ride with a 20-30 minute tempo effort mid ride. As your fitness improves you can increase the duration of the ride and the duration of your workout. As your fitness increases you can also get in 2 efforts with 20-30 minutes recovery in between efforts. Try to do these efforts on flat to lightly rolling terrain and keep the effort steady and consistent.