MADabolic Inc.'s name doesn't just refer to the crazy intensity of its interval training. In fact, "MAD" is an acronym for the three types of interval work its trainers most recommend: momentum, anaerobic, and durability.

• Momentum work hinges on fast-paced moves that build on each other, leading to what the trainers term "athletic chaos," and a good sweat.
• Anaerobic work consists of explosive, dynamic movements, such as jumping.
• Durability work features ungainly movements and awkward equipment that, over time, help stabilize your posture.

By combining these types of carefully structured intervals, using scalable work-to-rest ratios to provide an intense environment for each individual client, and switching up the specific moves every time—sometimes incorporating kettle bells, other times elements of boxing—the trainers keep client's bodies in a constant state of discomfort. That means no fitness ruts, and constant progress towards a fitter and more active lifestyle.