SIXSTAR Certified™ frameDerived from extensive biomechanics research, SIXstar Certification™ is a unique combination of the six key elements needed to deliver the most natural elliptical feel available. It focuses on all areas that impact the feel and comfort of an elliptical, including body positioning, handlebar spacing, elliptical foot path, pedal placement, elliptical access and the trainer's drive mechanism. Heavy-duty flywheel for a smoother, more confident rideIn addition to the SIXstar certified frame, the 4.1AE features a commercial-grade, 30-lb. flywheel for the smoothest ride possible. A heavier flywheel helps you stay concentrated on reaching your fitness goals by providing a consistent, effortless motion for every stride. Unique MAXtone™ pedal for a more intuitive workoutThe arched design of the MAXtone™ pedal utilizes the science of balance training to uniquely recreate a walking or running motion, while slimming and shaping leg muscles and glutes with ease. Your foot flows through the motion just as it does when walking on sand -- your heel contacts first, then rolls up to the toes for push off. This eliminates the "tingling foot" sensation found on other ellipticals, initiates core activation, and provides additional traction. Nike + iPod workout trackingJoin one of the world’s biggest workout groups with Nike + iPod, which automatically saves all your workout data directly to your iPod® so you can track your progress on nikerunning.com. Simply connect your iPod device to the Made for iPod connector and begin your workout while your pace, distance, time and calories burned are saved to your device. Once you’ve finished, connect the iPod to your computer, where iTunes syncs your workout data directly to nikerunning.com. Every workout is there, ready for you to review. More workouts, less routineEnjoy endless workout options with a variety of programming to match any fitness level and keep you challenged. Fro