While feeling the burn during a workout is generally a good sign, feeling the burn while sitting on the sofa means your sofa is in the fireplace. Engage in controlled, constructive body burning with today's Groupon: for $45, you get a one-month membership, including fees, and unlimited exercise classes at the Human Performance Center (a $101 value).

Human performers can take advantage of the center's indoor track, three pools, an array of exercise equipment, and a full schedule of fitness classes. Rows of Life Fitness machines magnify gravity's weighty influence over the entire pyramid of muscle groups, and more than 80 pieces of cardio equipment remind members that hearts are muscles, too. Lonely lifters can convene in a calendar of collectively powered classes, including yoga, aerobics, cycling, and mat Pilates. The aerobic Sweat! class tones the whole body with a combination of bosu, step, and weights, and Vinyasa yoga bends bodies from rigid breadsticks into limber pretzels. Heat-seeking muscles land their sights on the club's sauna, jacuzzi, or 90-degree therapy pool. Tai Chi and Reformer Pilates classes are not included.

A long list of Human Performance Center amenities includes locker rooms teeming with gratis grooming supplies, such as shampoo, conditioner, mouthwash, and fluffy towels. Bellies forced to share nutrients with needy appendages can replenish at the refreshment bar, stocked with water bottles ($1) and a selection of snacks for purchase. An Internet café allows nonstop stock monitoring, and on-site childcare for children 6 weeks to 12 years old keeps a watchful eye on your investments for you.