Aquajock
Cathlete
Thanks A jock, that's amazing! I haven't got access to a track... or anywhere I can run outside really... what do you suggest as a substitute? Just jogging on the spot?
Hmmmmmmmmm . . . do you have a stationary bike, elliptical or treadmill in your home workout environment? If so, you could jump on any of these and do about a minute's work at a comfortable (not zzzzzzzzzz and not nosebleed) pace, then jump off and do your intervals. OR, you could set up your step, and do basics, alternating knees, A-Steps, repeaters keeping the standing leg grounded on the step, elbow-to-knee steps, step-up and leg abduction, step-up and rear-leg extension, etc. Make the step as low or high as you want, depending on your fitness level and how moderate you need to make the intervals BETWEEN The Interval.
If any of these suggestions don't suit, develop a separate list of comfortable drills you can do in place (soft jogging on the spot as you noted, high-knee marches {as opposed to high-knee runs}, boxer's shuffle, heel jacks, etc.), and intersperse these with the higher-intensity drills from The List.
HTH!
A-Jock