There's boot camp brutal, and then there's this.  Tone House — the city's first extreme athletic-based group fitness gym — opened its doors only six weeks ago, touting its extreme hourlong workouts that focus on explosive exercise regiments, touted as one of the toughest workouts in the city.  With harness training, lateral jumps and group huddles, it makes sense then, that the gym's war cry is, "Unleash your inner athlete."  "This is a team environment," said the gym's founder, Alonzo Wilson, a former professional athlete and current Wilhelmina Fitness Model. "This is a place where everyone can make the varsity team."  The 2,000 square-foot studio, just north of Union Square, is decked out in black First Turf, a special kind of AstroTurf used by professional athletes, and the dim red lighting promises to get your blood pumping. Then there's the actual workout, which uses a rapid-fire string of high-impact warm-ups, including sprints, jumps, and turns.  Then it's onto resistance training courtesy of some very springy orange harnesses.  From there, there's a vicious routine of eggshells, burpees — vicious plank-to-push-up movements — and crunches, followed by even more resistance training targeting the core.  If that wasn't punishment enough, there's the part where you do lunges in harnesses for a minute, then some more push-ups for good measure.  Then, mercifully, there's a cool down. But, Wilson says, everything is on your own terms. "It's go at your own pace," he said ahead of our workout.  "This is going to be hard, but guess what? We are going to work out. It's not going to be a waste of time."  Hard bodies like the many professional fitness models that have come to haunt the Union Square spot have been known to burn 1,000 calories in a single workout. The record is 1,300 for the hourlong regime.  Without further ado, reporter Victoria Taylor and I decided to put their inner athletes to the test.  Let's get this out in the open — I am much more of a non-practicing yogi than I am a die-hard athlete.  I eked by on my middle school volleyball team and did moderately well at track and field. But a car accident and a bad leg injury put me on the sidelines.  So I was extremely nervous when Wilson started encouraging our 10-person class to jog around the dimly lit studio. "Fine," I thought. "That's easy enough. I can do it."  Then there was jumping over foam blocks. "Okay, that's still fine," I thought. "No pain no gain."  Next, it was onto the harnesses, something that delighted my inner-kid who always wanted to compete on "Global Guts." The harness slides on over the shoulders and has 80 pounds of resistance — meaning it's no cakewalk to simply move forward.  My muscles were crying out in agony, but there was Wilson, encouraging me and the rest of the Tone House athletes to keep pushing, fight through the pain.  When the nonstop burpees, crunches, and medicine ball squats become overwhelming, I quietly sneaked to a corner where, red-faced and heaving, I caught my breath.  The minutes crawled on, but with each new exercise, I allowed myself to think past the pain and think of how one sprint was probably canceling out the Shake Shack burger I had the day before.  Victoria and me were easily the least in shape of the bunch, but were always encouraged to push through and persevere.  By the cool down, I was shaking from head to toe and dripping in sweat (not an attractive look when our photographer was five inches from my face, snapping away). I felt lighter, exhausted and energized.  The next two days were agony, but on day three, I've started thinking — "I survived, and I feel stronger. If that was one workout, bring on the next."  Tone House reiterated something I already knew — I have neither the physical nor mental stamina for these kinds of workouts.  I was a competitive cheerleader in high school, so the kind of conditioning drills I used to do involved backflips and toe-touch jumps. Now, my exercise routine includes the elliptical, 20-minute yoga podcasts and Just Dance for Wii.  Still, I decided to try out the Tone House full-body class. I missed the black stretch pants memo and showed up in loose-fitting grey shorts and a sorority T-shirt from college.  Then, the actual workout started and I realized that I shouldn't have agreed to take the class in the first place.  My heart started racing and my face turned red before we had finished our first batch of sprints.  There, under the crimson glow of the lights, it was if I had been transported back to middle school gym class and was struggling to keep up with the pack.  Despite the encouraging words from the Tone House staffers, I was ready to quit after the foam hurdles. I was huffing and puffing like I was ready to blow a pig's house down. My chest hurt. I felt the toast with peanut butter I had for breakfast trying to repeat on me.  I stepped off to the side to catch my breath, joining in again for the harness, even though it made me feel like a human yo-yo.  That was about the point that I decided to take an extended time out. I was more or less down for the count, so I sat on the sidelines while Beth and the rest of the class powered through like champs.  I did jump back in for abs and stretching at the end of the session, but that was all my aching, exhausted, out-of-shape body could handle.  The small portion of the workout I did left me sore for two days.  No one made me feel ashamed for warming the bench. When I did participate, the instructors and other Tone Housers were supportive, saying things like, "You got this, Victoria."  Tone House wasn't right for me, but if you were, are or want to be a hard-core athlete, it could be a rewarding way to put your mental and physical strength to the test.  Tone House New York; 20 E. 17th Street, 2nd Floor, for classes and pricing please visit www.tonehousenewyork.com.  ON A MOBILE DEVICE? WATCH VIDEO HERE
The brutal workout at the Union Square studio, which combines harness training, lateral jumps, medicine balls and burpees, is not for the faint of heart. Daily Newsers Beth Stebner and Victoria Taylor put the extreme, athletic-based training to the test.