If you're trying to come up with something different to add to your workouts, consider the bear crawl. It would be a perfect fit in your conditioning work immediately following a resistance training (weight) session or on your non-strength days. Just a word of warning that they are quite beastly!
Bear crawls require you to move your body through space, which is a good thing. That is one reason why you will hear that exercises like squats, pull-ups, deadlifts, and push-ups are king. Moving your body through space with power requires more work. Bear crawls demand some coordination, which also expends energy. Concentration will help you do the move well. You may be surprised at how fast it will crank your heart rate up or knock the wind out of you.
Find a large open space or a clear straight path. On hands and feet, you will move foward just like a bear would. Remember, this isn't downward-facing dog on the move. Your knees should be slightly bent in order to keep your butt low and even with or slightly higher than your head. Your back should be relatively flat, not necessarily arched, but definitely not rounded. Brace your abs. Keep your head up or slightly neutral (you need to see where you're going).
My 9 month old grandson does this well when he doesn't like a hard surface on his knees!
One option is to add bear crawls as part of your metabolic circuit. Another option is to add them as a relief move several times in between your other exercises. They would be great for interval work, or even in between specific core work. You can bear crawl for time, or bear crawl around the gym or other pre-determined large space in a circle, or bear crawl down and back a straight path. Keep moving. This requires some guts because you are going to look stupid.
If people laugh, invite them to join you. They may:
a. not join you out of fear of looking even worse
b. join you and immediately stop laughing
c. join you, hang with you out of pride and curse you the next day
d. Both b and c.
Chances are they will stare and marvel while they continue their hour-long-or-more cardio session while reading a book. Then you can laugh all the way to the car knowing that you actually left some fat at the gym.