Your biceps turn your wrists, bend your elbows and flex your shoulders.
The standard version of the biceps curl covers the first two functions, but misses the last one, according to trainer BJ Gaddour.
To hit all three, you need to make a slight alteration to the exercise. Hold the flex at the top of the curl, then lift up your elbows 5-7 centimetres. (Watch Gaddour demo the variation in the video above.)
Make sure you stand along a wall while you do this. That’ll stop you from using momentum to cheat, and will put more emphasis on your biceps, says Gaddour.
For strength, do sets of 6-8 reps. For more endurance, do sets of 10-15-plus reps.