Short workouts can be highly effective and produce huge results if they’re done with intensity —
done with a no-nonsense approach. This also means there should always be a few
warm up rounds before going full speeds ahead, to properly prepare the mind and
body, and prevent injuries!
Here’s one of my
many “Furious Fives” metabolic workouts that hits every major muscle
of the body to the maximum, in no more than 20 minutes (or less time for the
more advance).
I call it Furious Fives because I designed each exercise within a circuit to be performed at a 5
rep max, each done back-to-back with little to no rest between exercise. This
means you would have to choose a load, or weight, which you can truly perform
only 5 repetitions in perfect form. 
Then, repeat the
entire circuit five rounds with minimal rest time in between rounds. So doing a
warm-up round to determine your ideal load or volume would be a good idea! ;)
If you’re a
beginner or intermediate, learning to modify the moves would be just as
effective for where you need to be. For example, instead of doing full jump squats forward, just do little hops forward. Instead of doing the close-grip
chin-ups, just use a machine to do close-grip lat pulldown at 10 rep max in
perfect form. (If you don’t have a machine, just do bent-over dumbbell
Instead of doing push-ups on your toes, just do them on your knees or place your body on the
floor and push off from there. 5 rounds too difficult? Do 3 rounds for now.
Weights are getting too heavy? No problem, just lower them as you need to. 

There are so many
ways to modify so you can slowly gain the strength and stamina that will take
you to the next level. And don’t worry, it’s still going to produce results for
you in every way, even with modification and all! :)