The following cross training will really challenge your quads, hamstrings and glutes. Definitely don’t do this cross training workout if you’re sore and recovering from some other hard lower-body workout.
I would save a workout like this for base training, if you’re coming off an easy workout, or you’re not actively training for a goal race in general.
The Workout: Start the spin bike at the lowest intensity, level 1.
Every time the minute counter turns over (e.g. at 1:00, 5:00, etc), adjust the level to match the number in the minute column. So at 2:00 you’ll set the level to 2, and you’ll increase the level by 1 every minute thereafter.
If the lowest spin bike levels feel too light and easy for you (for example you normally do easy spin bike sessions at level 4), you don’t have to start at or go down to level 1. If you generally bike easy at level 4, then for any level 4 and below you can just go at level 4. In this example, you do the first 4:59 at level 4, then at 5:00 you switch to level 5.
Once you get to a level that’s too tough, take it back down to a low, comfortable level. Then once the timer reaches 10:00, repeat the process by adding the digits in the minute column to determine the level, e.g. 11 –> 1 + 1 = Level 2… or in the level 4 example above, that person can just stay at level 4 for now.
If you can get to level 10 or higher without needing to slow down, great! You don’t have to add the digits at 11:00 or higher just yet. Just keep climbing levels until you need a break, then add the digits of the next minute to see how far down you can take the spin bike’s level. For example, say you get tired after 16:00 at level 16. Then at 17:00 you take it down to level 8 (17 –> 1 + 7 = Level 8).
If you’re a super strong cyclist and plan to go longer than 25 minutes, you may be able to reach the bike’s maximum level 25 (most spin bikes only have 25 intensity levels). If you get to 26:00 in this case, just take the spin bike back down to level 8 (26 –> 2 + 6 = Level 8… you must be super strong if that’s too easy for you; if so you can set the level higher to whatever level you prefer to cruise at). Then from there build the levels back up each minute. Do note that this workout method after you max out the bike won’t get you higher again than level 14 once you do so, so if maxing out is your goal and you can max out the bike then you may want to stick to 30 minutes or less.
Regardless of your abilities, you can repeat this level-up process until your spin bike workout is finished, whether it takes 20 minutes, 40 minutes, 3 hours, etc.
You could also do this workout on an elliptical, rowing machine, or ARC Trainer. But it can be very demanding to do more than recovery-level training on these devices. To do a workout like this on a machine like those may defeat the purpose of cross training unless you’re in an offseason, or are a triathlete or similar and this sort of demanding training is in line with your key workout needs.