The most secretive body parts are muscles, which hide behind layers of skin and appear only occasionally to help lift cars off trapped kittens. Flex your biceps in the absence of a cat emergency with today's Groupon: for $39, you get a four-week total fitness membership and two 60-minute personal-training sessions (a $129 value) at Total Fitness Clubs. This Groupon is valid at four locations in Rhode Island and Massachusetts: Bristol Total Fitness, Swansea Total Fitness, Seekonk Total Fitness, and Dartmouth Total Fitness.

All four Total Fitness locations house a panoply of muscle-building, heart-empowering fitness equipment, and more than 45 energetically instructed classes. From cardio kickboxing and kettlebell to Pilates and strength training, the fitness curriculum readies muscles and cardio systems to take on new challenges, such as running a marathon at the bottom of the ocean. Aspiring Zumbalinas can opt for Zumba classes to learn Latin dance moves; time-hindered humans can choose the power half-hour class, a core-strengthening and high-intensity cardio blast that burns calories like a flaming donut; and those in search of motivation can take boot camp, which comes complete with a military-esque instructor. More than 160 classes are scheduled each week; check each location's online class schedule for more information.

Total Fitness's certified muscle tutors help clients achieve a higher state of conditioning through the combination of one-on-one training and customized fitness programs. During a pair of personal-training sessions, Grouponers face an exercise routine based on an analysis of their fitness level and goals. Together with the trainer, you'll work to gain the tools and knowledge necessary to lose weight, tone muscles, and force poor health into a nearby friend who's in ridiculously good shape.