Gym goers seeking to boost their workouts might do well to aim for the less-used equipment beyond the busy rows of treadmills and elliptical trainers that dominate the center of the cardio floor, fitness experts say.

What the rower and the moving stairs may lack in traffic, they can make up for in effectiveness and intensity for people willing to think outside the box.

“What’s the best piece of cardio equipment? My short answer is the one no one’s using,” said exercise physiologist Tom Holland, author of “Beat the Gym.”

People tend to do what they’re good at and what they see others doing, he said.

Holland's favorite under-appreciated machine is the moving stairs.

“It’s tougher than the traditional StairMaster, harder to cheat on, and usually hidden away in dark recesses of the gym,” he said.

The treadmill is the most used machine, according to the trade association IHRSA (International Health, Racquet & Sportsclub Association), followed by resistance machines and elliptical trainers.

Stair climbers and recumbent cycles are among the most ignored, it says.

Hayley Zawadzki, personal training manager at the New York Health and Racquet Club (NYHRC) fitness center chain in Manhattan, favors the rowing machine.

“It burns a high amount of calories in a short amount of time, activates large muscle groups and is also good for training cardio endurance for marathoners and triathletes,” she said.

Zawadzki believes the rower is not very popular because it takes some guidance to use properly.

“As a warm-up, it’s a great way to loosen up the body, break a quick sweat,” she said. “Our trainers use it in circuit training as a cardio burst between strength training intervals.”

Nasario Meija, vice president at Crunch Fitness, said just as the rower is not only for athletes, the recumbent bike, which puts riders in a laid-back position, is recommended mostly for beginners.

“It does not require as much dynamic movement as a rower or a treadmill,” Meija said. “It’s a good starting point into a progressive cardio routine, or for people with lower back or knee problems because it’s very soft on the joints.”

Holland said it’s a mistake to always do the same machines in the same order.

“We need mix it up,” he said. “Start every workout with an exercise you don’t like, or use one piece of equipment you’re not used to, and the body will respond.”