I've been spinning regularly for the last several weeks so that when the weather turns I'll be ready to ride outside.

Now that it's starting to get warm and more importantly the time changes in two weeks, I'm looking forward to my evening rides after work (usually 25 miles on gravel).

The YMCA does offer an early morning HIIT class two days a week and I'm considering doing these along with my outdoor riding. I was wondering what the advantages and disadvantages of doing two HIIT classes a week along with riding 3 to 4 days during the week (25 miles each) and as many as 100 miles on the weekends.