Most creatures react to danger with a "fight or flight" response, which means they either box their opponent or commandeer a nearby blimp. Hone your martial instinct with today's Groupon: for $35, you get an intro pack of five cardio kickboxing classes at Judy's Group Fitness Inc. (an $88.48 value).

At Judy's Group Fitness Inc., accomplished instructors lead gym-goers through original, high-intensity classes that combine dance and martial arts to K.O. calories and release stress. During tension-blasting sessions of cardio kickboxing, exercisers unleash pent-up energy on lifeless body opponent blockers, who fuel each punch, kick, and jab by whispering one’s embarrassing childhood nicknames. As groups summon sweat with synchronized blows, spirited tunes imbue the studio with an extra dose of inspiration. To keep hands protected from misaligned strikes and dummies with a penchant for biting, cardio kickboxing participants are required to wear gloves, which can be rented or purchased at the facility.