Standing desks and exercise ball chairs are so last month. Here's the latest trend in law firm offices.

From taking a look at former Arent Fox litigation head Jay Hulme's desk, you'd never know what lies beneath: a treadmill. He had this wooden desk custom-designed by SPI Design in Alexandria to raise up to chest height with the touch of a button. From there, he works on everything from an amicus in the Supreme Court Riley case about warrantless cellphone searches (argued in April) to a high-profile antitrust dispute that tests DC courts' jurisdiction.

Jay demonstrated his desk in action (and let us try it out) in his corner office—he logs three to four miles a day. His speed is usually around 1.5 miles an hour, which lets him comfortably type and read his computer monitor. The treadmill is specially designed for office use, so it's made to minimize sound and go up to 4MPH. The same company also makes stationary bike desks.

Next door is litigation partner Jackson Toof, who picked up this treadmill desk a few months ago after long days representing the unsecured creditors' committee in the largest Chapter 11 bankruptcy filing in '13 had him sitting for six-hour stretches. (He also has to condition to keep up with four sons under seven years old.) It's from Gym Source in Falls Church. Now, he gets in more than 10,000 steps per day.