The E4000 Dual Action Bike combines upper and lower body exercise in one machine to give you one of the best aerobic workouts possible. Because you're spreading the workload over your major muscle groups, you can workout at higher intensities. For 20 years, air resistance has been the standard for dual action bikes. But with the latest magnetic technology offered in the E4000, you'll find that it's the quietest dual action bike in the market.