5 Hardest Gym Classes in America

Are you snoozing in step class? Can't motivate through mountain pose? "It's a signal that your regular routine needs a makeover. Take a more demanding class once a week to jump start your body and stimulate your senses," said exercise physiologist Linda Larue, who teaches a belly-burning 30-minute Core Transformer class at Equinox Fitness Club in West Hollywood, Calif. Try shaking up your stale routine with one of these tough-as-nails workouts held at fitness centers across the nation.

Warrior Workout at Pow! Mixed Martial Arts Training Center in Chicago
Why Take It? Super-sculpt your lower body and learn to fight like a pro.

During a 45-minute martial arts session, members wrap hands and wrists with protective tape for pounding the heavy bag, shadow boxing and jabbing while listening to deafening tunes from Van Halen and Black Crows. Class progresses from explosive combative choreography with knee strikes and blocks to kick combos and punching circuits. Class members warm-up by running up and down seven flights of stairs at the back of the gym!

Iron Yoga at studios around New York City
Why Take It? Amp up regular yoga practice by adding dumbbells to specific postures.

This intricate 60-minute class is so different from traditional flowing yoga sessions, said Iron Yoga creator Anthony Carillo, a triathlete who wanted to center his practice more on strength training versus flexibility. "As you hold weights with static poses, you deeply focus to stabilize your core and hone coordination," he said. Imagine holding an upright Tree Pose for one minute and then adding 30 biceps curls while hoisting 5-pound dumbbells.

Afterburner Race Day at Pinecrest Health & Fitness in Miami
Why Take It? To blitz 400 calories in under an hour and to boost pro cycling skills.

Spinning Master Instructor Scott Schlesinger teaches a 45-minute ride with rounds of heavy resistance so you're standing out of the saddle presumably pedaling up Mt. Everest, pumping out lightning-fast speed sprints and visualizing climbing your way up the side of a mountain range. After a thigh-pumping warm-up, the rider stays between a brutal 80 to 92 percent of maximum heart rate. Sprint intervals throughout Schlesinger's hard-hitting ride are triggered by the sound of jet plane engines roaring through the speakers.

The Amazing Workout at Lifestyle Family Fitness across the Midwest
Why Take It? Beat workout boredom by using every fitness tool in the health club.

The toughest -- and one of the most popular classes at all 34 LFF clubs -- is a two-hour challenge session that utilizes a combination of high-impact step aerobics, weight lifting with body bars and dumbbells, core work and circuits where you alternate heavy lifting with lightning-fast cardio (picture yourself doing knee repeaters off a step but also holding a barbell -- ouch!). Each teacher instructs class slightly differently, but guarantee you'll burn 1,000 calories per two-hour session.

Urban Rebounding at Bally Fitness Clubs across the United States
Why Take It? Ramp up cardiovascular endurance and bump aerobic workouts to the next level.

In this 60-minute class, you run two to three miles on a mini-trampoline -- with kicks, jabs, lunges and other moves thrown in. Creator J.B. Berns pioneered a high-energy workout to boost sports performance and kickstart your cardio by changing temp and moving your body aerodynamically. There's no jarring to your joints even during the high-impact exercises since the mini-tramp absorbs the shock without hurting knees or lower back. (The mini-tramp can hold 400 pounds.)

Prefer to hit the cardio machines instead of classes? Check out how to revamp your treadmill routine. Think your gym class is even harder than these ones? Let us know in the comments!

Fitness expert Nicole Dorsey Straff is a Los Angeles-based exercise physiologist and author, and frequently writes about diet, health and wellness.