Three minutes fast, three minutes slow - repeat for 30 minutes.
Searches jumped almost 3,000% as people looked for low-impact cardio that works.
Studies link it to lower blood pressure and better leg strength than steady walks.
Beginners, returning athletes, and anyone bored of step counts.
Five intervals on day one - that's it. Build slowly.
Two days of bodyweight work plus this routine and you cover the basics.