Firm Up That Under-Arm Trouble Spot With One Move

Amy Rushlow

To tighten and tone the back of your arms, most trainers will tell you to work your triceps (the muscles opposite your biceps). But your triceps, as the name implies, are actually three muscles. And toning one of them — specifically, the long head of the tricep — is the key to shaping that trouble spot and giving it a firm, toned look, says celebrity trainer Brett Hoebel, author of the 20-Minute Body.

Watch as Hoebel and Los Angeles-based personal trainer Ashley Somers demonstrate a fun exercise that zeroes in on the long head of the triceps while working your glutes (butt muscles), shoulders, and upper back.

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