Stationary bikes are an option for anyone who doesn’t own an outdoor bike, or for someone who might not want to brave rainy days or cold winters. Stationary bikes provide the same exercise and benefits as outdoor bikes, and some would argue even more because you can work hard continuously on a stationary bike whereas on an outdoor bike you can coast and use the gears for maximum efficiency. Another advantage to stationary bikes is that you can do speed or interval work on them with precision (you can easily monitor heart rate, the degree of tension, and the pedal cadence).
At the gym, you can try spin classes. I don’t know of any gym workout that people are more addicted to than spinning. People who spin regularly absolutely love it. Spinning classes are conducted on special stationary spin cycles where you can pedal very fast and hard and stand up comfortably and safely. Classes are led by boot-camp-like instructors who bark out when to speed up and when to slow down. It’s an awesome workout.
Recumbent bikes are an option for people with low back pain or for those who are otherwise uncomfortable on an upright stationary bike. The seats are very wide and comfortable (like an automobile bucket seat), and you sit in a reclining position with your legs in front of you to reach the pedals. The early recumbent bikes were very close to the floor and difficult for some people to get down to, but that was remedied with semi-recumbent bikes which are not quite as low. Check local sporting goods and exercise equipment shops in your area if you think a recumbent stationary bike might be for you.
Another option for indoor biking if you already have an outdoor bike is a wind trainer. A wind trainer is a flywheel device that temporarily converts your bike into a stationary bike. The way it works is that you attach your outdoor bike to it by resting the rear wheel on top of the flywheel, the front wheel in a cradle to keep it stable, and then pedal away just like a stationary bike. Resistance is provided by magnetic, fluid, or wind devices. Wind trainers are the least expensive, but they are noisy and have decreased in popularity. Magnetic trainers are very quiet and durable and change resistance as you pedal harder, but they do not do it progressively like you experience when riding outdoors. Fluid trainers are also quiet, but importantly, they do match the progressive resistance that you experience outdoors. There are also new magneto trainers that have the durability of magnetic trainers with the progressive resistance of fluid devices. Bike trainers are a great way to get you through the winter or when you feel like popping on your bike for an indoor workout, maybe in front of the TV to watch your favourite movie when you train.