I've seen some wild contraptions in my day, but the University of Minnesota might have the cutest. It has a "Bod Pod," a giant egg in which you sit to get your body fat measured.

The $50,000 machine, one of only three in the state, uses something called Air Displacement Plethysmograph technology to quickly test a subject's body composition without the need to get wet, pinched or exhausted. With a whir and change in pressure, the white pod quickly measures percentages of fat and non-fat and issues computer readings on lung volume and the resting metabolic rate -- the number of calories needed each day to maintain a person's weight.

University researchers say the machine is up to 8 percent more accurate at measuring body fat than are pinching skin-fold calipers, and much more convenient than full-body water immersion (hydrostatic) tests that often require 10 dunks and lots of exhaling.

Luke Carlson, founder of the Discover Strength training firm in Plymouth and a U of M kinesiology graduate student, said Bod Pod testing is an easy tool that will benefit many people. He has since incorporated an entire fitness training and results-based program around the machine for his clients, saying too many people cling to the weight scale as their gold standard of fitness.

"A scale only tells us half the story, because it measures just weight loss, but not exactly what we lost," Carlson said. "Most people need to lose fat and to increase lean muscle. With the Body Comp program, each person will learn precisely what their bodies need, right down to the number of calories to consume."

The Bod Pod is housed within the U of M's Physiological Hygiene and Exercise Science Laboratory at the Rec Center. It's mostly used for research and by the school's kinesiology students. But it's been available to the public since last spring for a fee -- $25 for students and staff and $40 for non-Rec Center members. However, groups can come in for one hour and pay a flat $100 fee.

Discover Strength client Jenna Nelson, 21, was back last week for a second reading after two months of a strenuous workout program that involved running, leg presses, triceps work and chin-ups. Before her training, she couldn't do one pull-up. Now she can lift her 112-pound frame three times unassisted. She wanted to know if her hard work would show.

"I'm doing this because I want to achieve certain fitness goals and this is a good way to test that," said the Hamline University student, while slipping into a swim cap and bathing suit and sliding onto the pod seat. (Minimal spandex clothing and a skull cap are required for an optimal reading.)

Student lab coordinator and kinesiology student Sarah Mork closed the egg's windowed hatch door, sealing Nelson inside. The sensation is like being enclosed in a round sound-studio chamber. Large magnets seal the door shut, while the inner and external air chambers exchange gases, measure volumes and download data into an adjacent computer.

After three 50-second readings, Nelson sprang from the Bod Pod while Mork got to work printing out her results. "It's a very good result!" she told Nelson, marveling over the fact that Nelson lost nearly 4 pounds of fat and gained 4 pounds of muscle since September.

Carlson peeked over. "For her to have a 3.3 percent drop in body fat percentage is incredible. The average person working out like crazy may lose weight. But she didn't lose any weight," he said, noting that Nelson's body composition changed instead. "This tells you whatever she is doing is working. And she would never be able to assess that just on a scale."

Dee DePass • 612-673-7725