High intensity training is a staple in my weekly workouts. Essentially, any routine that gets me in and out in 30 minutes or less (thinking Kayla, Plyos from P90X and 21DayFix, and more) are done at least twice a week. Friends who live in the NYC-area have told me, more than once, that I "have to try FHITTING Room." That it was in my fitness wheel house. So we rallied a few troops from work and went during my last week long trip. I didn't really know what to expect but I was ready to sweat.
The room holds 24 participants and class is run by two instructors. I loved the added instructor. It means you can't get caught slacking at all, and the energy remains high throughout the workout. Ben and Farouk taught our class, and they were just really fun to be around. I don't remember looking at the timer once because they were keeping our spirits up.
The workout itself was challenging in the sense that it got my heart rate up and I was sweating VERY quickly. It was broken up into a "warm up" (term used loosely), strength, circuit, and then finally a partner workout.
The Warm Up: we did 30 seconds of jumping jacks, jump rope, air squats, hip openers, mountain climbers and then more jumping jacks. I was certainly warm up the jump rope and sweating buckets by the second set of jumping jacks.
Strength: I didn't go extremely heavy here, probably used just about a 12-15lbs depending on exercise, but really started to feel it when we were doing the bent over rows with kettlebells. Each move was a minute long, and we did it with the entire group. This was done twice through.
Circuit: Then they broke us into four groups and we went through four different exercises twice. Each station lasting a minute. This included rowing, KB presses, KB step ups and KB swings.
Partner: Finally, if my arms weren't tired enough at this point we did 4 rounds for each person and you had one minute to finish nine dumbell thrusters to a medicine ball and nine burpees. And at the FHITTING room, you go all the way to the floor for the burpees. 
This workout was no joke. I was honestly sore for two days following, and couldn't believe it. The workouts change daily, so you can be sure you never fall into a rut.