I have just started training for my first Sprint, and the only bike I own is 12+ years old and no longer fits (my knees hit hit the handlebars!!). Money is tight for the next 4 months, until my better half is done with school and back to work. There is not a bike that I can borrow, as all my biker friends are significantly smaller than I am. Could I do all my bike training until April/May through spinning classes or an indoor trainer at the gym? I haven't been on a bike in at least 10 years and know I need a lot of ride time to get into Tri shape. Please help with any ideas you might have, thanks.