The set-up for turbo-training: fan, towels, water, HRM, and proper bike-mounting on the trainer. Notice my dropped wallet - thus, I could not order pizza on-the-move like Dean Karnazes.
You decide to amplify the intensity, which can be a premature move unless premeditated and committed to. Endless and mindless spinning leads to a fixed pattern that is hard to shrug off. You need to break the habit (of incessant spinning at a fixed speed/power unless you are doing an aerobic session) by doing something else. You insert a specific training set, be it a series of 30-seconds all-out sprints, or a more calculated 10-minute moderate pace with your highest gear. Of, you can elect to do a more challenging (and painful) 30-minute time trial on a high-gear. You can also create a hill, by raising the front wheel with a phone-book. You can create a ‘party mix’ of various permutations and combinations. Commit to these complementary sessions long enough, and you will experience new growth in your riding abilities. Come rain or shine, you will save time because your set-up is ever-ready for an aerobic session or spinning class!
However, there are repercussions. You will need to mop up a big puddle of sweat and other residue – evidence of a spent session. Such is the consequence of training in private. How to Ride Inside: Indoor Trainer Workouts for Cyclists.