High-energy bike work that torches your legs and lungs.
Keep tension in the pedals on climbs and don't bounce in the saddle when you sprint.
Spinning alternates seated grinds against heavy resistance with fast, light-flywheel sprints, so your heart rate swings between zones instead of parking in one. That interval structure is what makes it such efficient conditioning, you get both the steady aerobic base and the hard anaerobic spikes in a single session. It is also joint-friendly, which is why it works as cardio for lifters who want their legs conditioned without pounding them.
An easy spin actually helps recovery by pushing blood through the legs. A sprint-heavy class the day after squats is a different story, so match the intensity to what your legs have left.
Saddle roughly at hip height when standing next to it, so your knee keeps a slight bend at the bottom of the stroke, and handlebars where your back stays comfortable. Two minutes of setup saves an hour of knee complaints.
Bouncing means the resistance is too light for the cadence. Add enough tension that your legs are driving the pedals, not being thrown by them, your power output goes up and the bouncing stops.
