Endure the exercises for the given amount of time, don't stop! You can lower the intensity of high knees (don't bring your knees as high) as you tire out but keep on moving. If you drop the plank, pick it back up as soon as you can and continue. Even if you pause or stop, start again as soon as possible keeping the break to the absolute minimum. Earn the extra credit for this challenge: no breaks, no pauses throughout.