Which bike - a fixed gear/single speed bike, or a road bike with multiple gears - is the best for a good workout?
I'll explain my situation a little more and my thoughts and then I'd appreciate some feedback. Right now I have a single speed bike which I got cheap off of Craigslist. It works well but needs a few upgrades to get in good shape - the tires are worn out, the seatpost is too short, etc. I'm debating whether I should sink the money into this old bike or get a new bike, and my wife said I can go ahead and look at a new entry-level bike
Anyways where I live is relatively flat, with a few gentle hills. I've been bike commuting to work for nearly a month on the single speed and it goes fine (9 miles round trip 5 days a week). I bike 20-40 miles on the weekends, 10-20 miles at a time. At the end of 10-20 miles I feel completely spent. Total of 65-85 miles a week.
Now my goals are twofold:
1. Commute to work
2. Stay fit and lose a few pounds (6'0", 177lb and dropping) both by my commute and biking recreationally on the weekends
Now I love the single speed bike for the sheer simplicity of it. But my concern is this: is it limiting me from going long distances, or do I just need to build up leg strength? It seems to me from reading that most fixed/ss bikers never really attempt long distances, and I'd like to be able to put on 40, 50 or more miles over a weekend. I know typically fixed/ss bikers are city dwellers but even reading about those who ride recreationally, they tend to be in shorter rides.
Secondly, which bike will give me a better workout? I guess ultimately if you kept a geared bike in one gear, it's like a single speed... but is there some inherent advantage to the single speed, ie, forcing yourself to power up those hills instead of shifting down to a lower gear?
Thanks for the input.