I want to burn fat and improve my conditioning, how should i train? how many minutes, how many watts?
Vary your workouts. How many days a week are you planning on riding? I like to do an hour at a time with a lot of intervals mixed in. Begin with a moderate warm up and then go for two or three minutes at a time of either hills or sprints (or both) give yourself a 30 second recovery and then repeat. You can work in all kinds of stuff to break it up and make it less boring. Long gradual hills to build strength and endurance, fast sprints to get your heart rate up. I don't know if you have them over there, but I would suggest attending a spinning class at the gym to get an idea of how they structure their workouts. If you do a strenuous workout one day, do a long, moderate ride the next. Also, I've been doing a ten minute jog before and after riding and it's good to test that transition. It gives your body a challenge to move differently and adjust.
thanks for your detailed answer. of course we have spinning classes, maybe i'll check one out some time. so you think 40 minutes a day at the same rate won't bring that much results? because i like to step on the bike and get in a meditational state where i just switch off and don't have to mess with the knobs every few seconds.
You can do that, but your body will adjust to it and you won't be getting as much benefit. If you like to zone out try doing two, 20 minute intervals. Start with a long climb, every 5 minutes up your resistance and then in the last 5 minutes add a lot (to the point that you can't stay seated for more than 30 seconds) and finish with a hard climb in and out of the seat. Take the resistance down for two minutes to rest your legs and get some water and then repeat. Just pedaling along will burn calories but you need to challenge yourself to really see some results.