If you're looking for a great all over workout, look no further. Tap into multiple muscle groups and get that heart rate pumping with the rise and grind, no equipment needed, full body workout.
If 5 rounds is too much, simply cut it down to 4, but don't sell yourself short! The built in rest gives you just enough time to give it all you've got each round.
Walking Lunges - If your knees aren't the best, get on all fours and do 20 leg lifts (completing 10 on one side before the next)
Push-Ups - If you're not quite getting the full range of motion from plank position (chest almost completely to the floor), drop to your knees. Then, make sure you go all the way down! Even if that means releasing tension at the bottom and lying down for a moment, then peeling yourself back up. Completing the full range of motion is the only way to truly build the strength needed to complete push ups from the plank.