I love a HIIT workout. It boosts my metabolism, increases my VO2 max so I can work harder for longer, and does that in a relatively small amount of time. Adding an element of resistance training to a HIIT session is even better, improving my muscular endurance too. I went on the hunt for a HIIT workout with a strength component—something that would work my whole body, but with slightly more emphasis on strengthening my legs— and came back with this routine from personal trainer Bradley Simmonds. I also didn’t have too long to spend in the gym, so the fact that it was 12 minutes long was ideal.All you’ll need for this workout is a pair of dumbbells. I could tell this routine would be intense, so I stuck to light weights throughout. I recommend getting your hands on an exercise mat as well since the final movement, the bicycle crunch, is performed lying on your back.Watch Bradley Simmonds’ WorkoutThe workout is structured so that you work for 30 seconds then rest for 10. Simmonds recommends repeating the circuit between three and five times in total.I completed three circuits, following it with a short arms and abs workout. Even when I did just three rounds, I found it a challenging workout, especially as there isn’t a longer rest period at the end of the round. I definitely noticed the emphasis on leg exercises, but my core was also set on fire by the routine—special shoutout to the lizard climbers, my new arch-nemesis.If you plan on using this workout as a standalone session, don’t forget to warm up thoroughly, and just as importantly make sure you keep moving to let your body warm down slowly.If you have a pair of dumbbells at home and are looking for more intense workouts to add to your repertoire, try this longer dumbbell HIIT workout. Or, for a similarly short routine, this dumbbell circuit works every muscle in just 15 minutes.