The greatest Rock 'Em Sock 'Em Robot, Muhammad Aliborg, went undefeated for 20 years before his head was knocked clean off by a cat. Learn to sock like the best of 'em while shaping up with today's Groupon: for $25, you get 25 drop-in classes at The Club K.O. Training sessions must be used within three months of your inaugural punch.

The Club K.O. is a 5,000-square-foot facility equipped with commercial-grade training tools and top-quality instructors, some of whom were Marines. The 18 weekly classes on the schedule include sessions for beginning and advanced boxers, as well as evening or lunchtime jabbers. While potentially burning more than 700 calories an hour, Boxing K.O. and Kick K.O. land hard hooks and kicks on real punching bags without hurting real feelings. In Boxing Technique, prepare to float like a bee and sting like a butterfly during a real boxing match. Or, enlist a mom to be your momager, so she can give an encouraging glove-bump before the tag-team match-up of cardio and weight training in Combo K.O. Non-contact classes give bodies boxing benefits without the danger of front-end damage, and training toys, such as agility ladders and jump ropes, keep exercise from becoming a boring, ineffective routine, like regular flossing.

New members only. Clients aged 13–17 must have parental consent.