I want to start off by saying I am writing this due to my frustration in my training. This led me to do some research and therefore I wanted to share my thoughts.
What is a Bike Trainer?
A bike trainer is a cycling tool that is designed to allow you to ride your bike while remaining stationary. There are a few different types, but I am not going to go into full detail on each one. Rather, the two most common trainers are one where you put your whole bike on the trainer (first picture above) or one where you remove the rear wheel and hook up the bike via the cassette.
For a base model trainer, you will be able to adjust resistance of trainer, in addition to shifting your gears for additional resistance adjustments. The higher models you go up, the more features you get. A typical benefit to cassette trainers is that if they are "smart" you will get power as one of the tracked metrics. Now, if you already have a power meter on your bike, this might be a moot point. Some trainers will even allow you to adjust for hills.
What is a Spin Bike?
A spin bike is a stationary upright bike that is designed to mimic the ergonomics of a road or triathlon bike. Similar to trainers, the higher end you go, the more metrics and hill abilities you get. As opposed to having wheels like a traditional bike, it basically has a front "friction-less" disc that connect back to the crankset. This whole system is designed to be as low friction as possible, with either a digital or manual resistance adjuster.
What is the Difference
From a pure cardiovascular workout standpoint, both types are great. You can get a wonderful burn and enjoy the benefits of biking while indoors. You can also do various strengthening drills on both, such as one-legged drills. However, this is mostly where their similarities end.
A spin bike is going to be very deceptive to the rider when comparing to real road conditions while on a real bike. Due to the mechanical design of a spin bike, it avoids a lot of the friction and mechanisms you get in a standard bike. Granted, there are road and triathlon bikes designed to reduce friction, but nothing to the level of a spin bike. Also, there is just no beating training on your own bike. There is a completely different feel and balance, even when stationary, to your bike on the trainer versus a spin bike. Your bike is, or should be, set perfectly to your dimensions. A spin bike can be adjusted of course, but most aspects are different. A spin bike also avoids a crucial aspect of road biking; shifting. Since you can't coast on a spin a bike and you adjust frictional resistance versus shifting, you don't get the same experience you would when out on the road. Granted, a trainer is not going to let you coast either, but you will be able to shift.
My Personal Experience
When I first got into road biking, it was already late fall and I started with a spin a bike. I worked up to some of the max resistance of the spin bike while maintaining a very high RPM. When spring came around and I bought my road bike, I expected to hop on and fly through any obstacle with ease and at lightning fast speeds. My first go on the bike I fell over from lack of balance. My first hard bend, I crashed. My first monster uphill, I couldn't even make it up. My first downhill I already wiped out. My first massive side gust, I got blown over. My first race, my time was double what I expected.
My point here is that despite doing all of the recommended drills and training like crazy on a spin bike did virtually nothing to help me with actual road biking. This is a very common theme for most cyclists. This is why most cyclists you will talk to have a trainer at home, or go to a gym where they can hook up their bike to a trainer.
Final Thoughts
I know this was a bit lengthy of an article, but I wanted to stress there is no substitute to training on a bike versus a spin bike. If you race, I can only recommend using a trainer, except for when you just want to get a good cardio workout in to work on endurance. Otherwise, stay away from the spin bikes. However, if you don't have the space for a trainer and spinning is your only option, definitely do it. Just make sure the second you can get back on your bike, you do it.
