Originally Posted by
caloso
There are things you can do at a gym that address fitness issues that a bike won't. Upper body strength, for example. And there are things you can do at a gym that will improve your bike fitness too, such as flexibility, core strength, and lower body explosive strength.
I find the local Trail Stewards is good for upper body work; shoveling wet gravel (or wheelbarrowing it up and down hill for that matter) for three hours is no joke. Pity it's only once a month.