This 20-minute dumbbell workout uses "supersets" to build muscle, but how does it work?

Looking for a good dumbbell workout to target your back and biceps—those parts of your body a push-up can't reach?

This workout from online PT Caroline Girvan, using a set of the best adjustable dumbbells, takes just 20 minutes. You might not think you can get a satisfying, muscle-building workout into such a short space of time, but Girvan uses "supersets" to cram in as many muscle-building moves into this dumbbell workout as she can. 

Supersets, despite their intimidating name, are actually a very simple concept: once you finish one exercise, go straight into something different, and rest after you've finished both exercises. For example, you might do a set of 10 push-ups, a set of 10 dumbbell rows, and rest for 30 seconds before doing both all over again.

Girvan says: "This workout is going to be made up of primarily supersets: 45 seconds of work, 45 seconds of work, and 30 seconds of rest. Most of the supersets will be performed for two rounds."

Check out her full workout below:

Dumbbell workout: Why do supersets?

Supersets are efficient. Naturally, you're doing two moves one after the other, so combined with shorter rest times you're going to be able to squeeze in more work than you might do during a "conventional" workout. This makes them great for early morning and lunch-break dumbbell workouts. 

However, they're also backed by science. Research from the European Journal of Applied Physiology found that two-move supersets were likely to be much more efficient than single-set workouts, and likely to create an increased hormone response. That means more testosterone, helping you to build muscle, and a decreased production of cortisol, the human "stress hormone". 

Cortisol not only activates your "fight or flight" response under pressure, but it also encourages your body to store fat. Supersets are likely to lower unnecessary cortisol production, which means you'll be storing less fat overall. 

Girvan's workout works your rear delts and lats (like our other best back workout), your biceps, and core. Using moves like renegade rows, which require you to hold a plank while you lift a dumbbell, she creates instability, which means your abdominal muscles work harder to keep you upright. Want a strong core as well as a muscular back and less body fat, all in 20 minutes? This is the dumbbell workout for you. 

However, if you don't have a set of dumbbells, consider picking up a set of the best resistance bands, which are just as versatile and a little cheaper.