This 5-Minute Ab Finisher Is the Reincarnation of P90X’s Ab Ripper—and It Builds a Stronger, Leaner Core

From flip phones to frosted tips, the 2000s are back. And now, it's the turn of the century’s most iconic workout program: P90X.

If you’re too young to remember, the original, 12-DVD set was a monster, and was said to have sold more than four million copies on the promise that wild-eyed trainer Tony Horton and corn-cob pullups could get you “totally ripped” in 90 days with a pullup bar, bench, and set of dumbbells.

In the reincarnated P90X, now called “Generation Next,” the magnetic...