In martial arts, the feet are used to defend the body against gangs of attacking math teachers, as well as scratch the head thoughtfully while the brain deflects their hurled calculus equations. Sharpen your limb skills with today’s Groupon: for $15, you get a five-punch pass for kickboxing classes, to be used over a 12-month period, to Bad Boy Gym in Royal Oak (a $50 value). Bad Boy schedules more than 25 classes per week.

Named after a real-life boxing prodigy whose talent first burst from its egg when he was 4, Bad Boy recently renovated its old-school boxing gym with a newborn boxing ring and forests of brand-new heavy bags. Kickboxing Beginners teaches fledgling feet to combat bags, bodies, and haughty stuffed animals before graduating to the regular course. A variety of hybrid classes torques muscles even tighter by mingling kickboxing with cross-training, Pilates, and extreme hopscotch.

Bad Boy also keeps its guests in fighting shape post-class by inviting them into a just-unwrapped gym full of free weights, weight machines, and cardio equipment. For a grittier workout, exercisers can hoist kettlebells and juggle sledgehammers in the new military-style training room.