The elliptical is definitely a joint-friendly machine, but it can get a bit monotonous. This workout is pretty straightforward, but it's full of quick speed changes to beat cardio boredom. Plus, intervals are great for burning extra calories and boosting metabolism.
*SPM = Strides Per Minute
If you have trouble slowing down in the recovery periods after sprinting, try going hands free. It will force you to slow down and challenge your core. Choose an incline and resistance that feels challenging but doable. Have fun!