According to Bommarito:
Most of the HIIT exercises advised by Bommarito may include the use of gym equipment. If these machines or tools are not accessible to you, you can always perform the exercises suggested by Richards.
HIIT – Stair Stepper Machine Interval Workout
This workout can be performed on a stair stepper machine by Cybex Arc, Versa-Climber or whatever stair climbing equipment you have wherein the foot is steady and firm on the pedal. You also have to adjust the resistance level of the machine. It must be a bit difficult that you have to “huff and puff” at the last few counts. The distance between the right and left leg when stepping up and down must also be adjusted after each set.
How to do it:
20 minutes of the exercise with max out at 30 minutes.
(30 seconds of stair stepping and 30 seconds of rest for a total 1 minute. It means that the entire workout will be composed of 20 to 30 sets.)