Our product picks are editor-tested, expert-approved. We may earn a commission through links on our site.

Add some long pauses into your next arm day workout for more gains.

If you believed 21s, the classic arm-building protocol, couldn’t get any more brutal, put that thought—and your biceps—on hold.

We bring you the latest in biceps innovation, the iso-hold 21s, to up the tension and increase the pump for your effort. The iso-hold the latest Eb and Swole workout, as Men’s Health fitness director Ebenezer Samuel, C.S.C.S. explains how you can extend the work even more than his previous adjustment to 21s.

Before we show the tweak, let’s refresh the basics of the 21s workout:

●Begin by curling a pair of dumbbells from the bottom position to midpoint for seven reps.

●From there, perform seven reps from midpoint to the top position.

●Finally, perform seven curl reps in the complete range of motion.

For Iso-Hold 21s, we change up the start slightly to ramp up the time under tension.

●Start right away with a seven-second iso hold, keeping your forearms parallel with the ground. When you're in this position, make sure to rotate the dumbbells so that your palms are fully facing the ceiling.

That sets the tone for what comes next.

●After seven seconds, go into the first wave of seven reps, starting from the bottom to midpoint. The seven seconds of holding should have you ready to focus on maintaining a good squeeze throughout the exercise.

●Once you hit the next seven reps, it’s back to seven seconds of an iso hold before going seven reps from parallel to the top.

●Now you know the drill: After the seventh rep, assume the iso-hold position for another seven seconds before hitting seven full range of motion reps.

One note: When you hit that parallel position during the iso-holds, make sure your palms are fully turned to the ceiling, focusing on getting that pump and perfect contraction. That happens when our forearms are parallel to the ground.