How Does an Anti-Gravity Treadmill Work?

iStock/nd3000
iStock/nd3000

The "anti-gravity treadmill" was originally invented by Robert Whalen, a biomechanics researcher at NASA Ames Research Center, in the 1990s.

Whalen knew that astronauts on the International Space Station have to exercise for hours each day to combat the loss of bone mass and muscle in microgravity. But the treadmill on the ISS has always left a lot to be desired. In lieu of gravity, it uses straps around the shoulders and hips to anchor the astronaut to the treadmill. The bungee system doesn't do a good job of replicating the magnitude or types of force that runners experience here on Earth. And to make matters worse, it's pretty uncomfortable to run in. Astronaut Sunita Williams, who was the first person to run the Boston Marathon in space, described her experience in a NASA press release: "During the marathon my foot sometimes went numb and tingly from the straps' pressure on my hip. Also, I had to use moleskin where the harness rubbed my neck raw."

Whalen designed a treadmill that would let astronauts run in a more natural way. The design, patented in 1992, encloses a treadmill and the astronaut's lower body in an airtight chamber. Lowering the air pressure inside the chamber pushes the astronaut down, simulating gravity. Whereas the ISS's old treadmill allowed Williams to run on about 60 percent of her Earth weight, Whalen's treadmill would have allowed her to exercise at her normal Earth weight. That's important for keeping the muscles and bones healthy for when astronauts get home.

But Whalen's idea never made it off the ground. In 2005, the technology was licensed to a company called AlterG, which appears to have coined the term "anti-gravity treadmill." Instead of adding weight to astronauts in space, AlterG uses the technology to take the weight off of rehab patients recovering from leg and foot injuries.

AlterG's product looks like a bounce house for your lower body. To use it, you put on a pair of tight neoprene shorts. The shorts have a sort of skirt attached, and the skirt is lined with zipper teeth. You step onto the treadmill, inside a hole in its plastic casing, and zipper yourself in so that, from the waist down, you're encased in an airtight plastic bag. As you stand there, the treadmill measures your weight, and you tell it how intense you want your workout to be. The the machine uses "unweighting technology" to make you feel up to 80 percent lighter—so if you weigh 100 pounds, you could feel as light as 20 pounds on the treadmill. The terms "anti-gravity" and "unweighting technology" are enthusiastic descriptions for what the machine actually does, which is inflate the plastic bag around your lower body to lift you off the surface of the treadmill.

Despite its perhaps overhyped name, the anti-gravity treadmill seems to be doing good things in physical rehab clinics, because it allows patients to exercise without exacerbating an injury. Here's NASA's glowing review of the anti-gravity treadmill:

Professional and college sports teams across the United States feature the AlterG treadmill in their training facilities. Injured soldiers walk and run with the technology’s assistance at military hospitals and rehabilitation centers. Seniors get essential exercise using the support the machine provides, as do people with bariatric weight issues who cannot normally support their own weight. The treadmill has been a proven option for neurological uses as well, including helping patients re-learn proper balance and gait and transition to independent movement after traumatic brain injury.

A variety of peer-reviewed studies also suggest it helps people get back on their feet again.

A true anti-gravity machine—one that is not acted on by gravity—would of course have even more exciting applications, particularly in spaceflight. Unfortunately, for now at least, those machines only work in science fiction.

Take a 40-Minute Virtual Tour of the Winchester Mystery House

BrookePierce, iStock via Getty Images
BrookePierce, iStock via Getty Images

Taking online yoga classes and watching soothing animal live-streams isn't the only way to cope with isolation. If taking a virtual tour of one of the most allegedly haunted places on Earth is more your style, now you can check out every baffling nook and cranny of the Winchester Mystery House on the landmark's website.

Along with many public businesses and institutions across the country, the Winchester Mystery House closed earlier in March in response to the novel coronavirus pandemic. A visit to the site in person normally costs up to $54, but until it reopens, anyone can take a virtual tour of the estate for free.

The Winchester Mystery House is one of the most notorious pieces of property in California's Bay Area. Constructed between 1886 and 1922, legend says Sarah Winchester built the unusual abode to ward off the vengeful spirits of people killed by Winchester rifles. (The founder of the Winchester Repeating Arms Company was her father-in-law.) The home's bizarre layout, which includes stairs that stop at the ceiling and doors that open to nothing, may reflect her fear-driven compulsion to keep building.

Today the Winchester Mystery House is an iconic California landmark. It's a bucket-list destination for ghost hunters, and it's even been immortalized as an elaborate LEGO sculpture. To see the inside of the structure, and to learn more about its history, you can take the 40-minute virtual tour here. If you're looking for more ways to support the attraction while it's closed to visitors, consider buying a discounted ticket voucher now to use when the house reopens.

Super Spreader: The Strange Story of Typhoid Mary

Mary Mallon, an unwitting typhoid carrier and unwilling hospital patient, in the early 1900s.
Mary Mallon, an unwitting typhoid carrier and unwilling hospital patient, in the early 1900s.
CBS Sunday Morning, YouTube

In the winter of 1906, Mrs. George Thompson called upon Dr. George Soper, known around New York as an “epidemic fighter,” to investigate the source of a typhoid outbreak that had occurred among renters in her Oyster Bay summer home several months prior.

After finding no issue with the well, the outhouse, the food supplies, or any other part of the property that might have generated germs, Soper considered the possibility that the carrier could have been a healthy person—an idea that wasn’t widely accepted at the time. By process of elimination, he landed on a likely culprit: the cook, a 37-year-old woman named Mary Mallon.

typhoid mary newspaper article from 1909
An article published in The New York American on June 20, 1909.
Lupo, Wikimedia Commons // Public Domain

Mallon, described by the other servants as “not particularly clean,” had arrived at the Thompson home on August 3, 1906. Just weeks later, between August 27 and September 3, six out of the house’s 11 occupants had contracted typhoid fever. Though most of her dishes were hot and prepared at temperatures that would have killed any bacteria, Mallon had served ice cream with fresh peaches one Sunday, which some of the house guests ate with gusto.

Before searching for Mallon herself, Soper followed her trail of employment all the way back to September 1900, unearthing a total of seven households in New York and Maine that had suffered typhoid outbreaks during Mallon’s tenure.

“In nearly every instance, a well-to-do and socially prominent family, soon after moving from the city to the country for the summer, experienced an outbreak of typhoid fever. In no instance had its cause been satisfactorily explained,” Soper recounted in the Bulletin of the New York Academy of Medicine. "The cook always left soon afterward. She had never been suspected."

Soper decided it was time to track Mallon down.

A Mean, Unclean Quarantine Queen

In early 1907, Soper paid Mallon a visit in Manhattan, in an old-fashioned house on Park Avenue and 60th Street where she was working, once again, as a cook.

“I was as diplomatic as possible, but I had to say I suspected her of making people sick and that I wanted specimens of her urine, feces, and blood,” Soper wrote.

Mallon seized a carving fork and chased Soper from the premises.

After another unsuccessful attempt to reason with Mallon, Soper asked New York City’s Department of Health to intervene. So Dr. Sara Josephine Baker came calling at the Park Avenue estate, and Mallon made a run for it, evading capture for three hours before police found her in a neighbor’s shed and deposited her into an ambulance.

“The ride down to the hospital was quite a wild one,” Dr. Baker recalled.

Mallon was taken to an isolation ward at Willard Parker Hospital, and doctors tested her feces three times a week between March 20 and November 16, 1907. Salmonella enterica enterica serovar Typhi, the bacterium that causes typhoid, was found in nearly every sample. Soper visited Mallon at the hospital to explain why she had been confined for so long (and also to determine the possibility of securing her release).

“When you go to the toilet, the germs which grow within your body get upon your fingers, and when you handle food in cooking they get on the food. People who eat this food swallow the germs and get sick,” he told her. “If you would wash your hands after leaving the toilet and before cooking, there might be no trouble. You don’t keep your hands clean enough.”

Mallon, frustrated and lonely, wasn’t very receptive to his advice, and refused to give doctors permission to remove her gallbladder, which they suspected was the source of the germs. There’s a good chance that this was true, since recent scientific studies have shown that many asymptomatic typhoid carriers store typhoid bacteria in their gallbladders. When their gallbladders empty bile into their small intestines, some of the bacteria goes with it, and then gets excreted in their stool.

“No knife will be put upon me,” Mallon told the doctors who requested to remove it. “I’ve nothing the matter with my gallbladder.”

typhoid mary cartoon
An illustration of unknown origin showing how Typhoid Mary spread bacteria through food.
National Museum of Health and Medicine, Flickr // CC BY 2.0

Soon after that meeting, Mallon was relocated to a bungalow near Riverside Hospital on New York's North Brother Island. Her quarters, originally built for the superintendent of nurses, were more spacious and more comfortable, but Mallon was still treated like a dangerous outcast, isolated from the rest of the island’s inhabitants.

Two years after her arrest on Park Avenue, Mallon sued the Department of Health, claiming that she had been imprisoned without due process of law—in fact, she hadn’t even been accused of a crime. Dr. William H. Park, the bacteriologist who had tested Mallon’s feces, took the stand to explain how Mallon—though seemingly healthy herself—was an asymptomatic typhoid carrier. Both sides presented compelling arguments, but the court simply didn’t want the responsibility of determining whether Mallon was fit to rejoin society.

They dismissed the case altogether, and a defeated Mallon returned to North Brother Island.

Life As a Culinary Renegade

In February 1910, Riverside Hospital finally decided to release Mallon on the condition that she promise not to work as a cook and “take such hygienic precautions as will protect those with whom she comes in contact, from infection.” She agreed to the terms and left the island.

What she didn’t do was keep her word. For the next five years, Mallon flitted from kitchen to kitchen in the area, introducing herself as “Marie Breshof” or “Mrs. Brown.” She cooked in a restaurant on Broadway, a hotel in Southampton, an inn in Huntington, and a sanatorium in New Jersey. Typhoid followed Mallon wherever she went, but she never stayed in one place long enough to rouse suspicion.

That is, until 1915, when Dr. Edward B. Cragin solicited Soper’s help in detecting the cause of a typhoid outbreak at New York’s Sloane Hospital for Women. More than 20 people had fallen ill, and the other servants had taken to calling the cook “Typhoid Mary”—a sobriquet that newspapers had used for Mallon during her solitary confinement.

After Soper positively identified the woman he knew to be Mary Mallon, the hospital alerted the Department of Health, and Mallon was whisked right back to North Brother Island. This time, she didn’t resist.

The Lonely Legacy of America’s Most Famous Asymptomatic Carrier

Mallon lived out her remaining 23 years in the lonely riverbank bungalow, processing tests in the hospital laboratory and making occasional sojourns to Queens to visit a family she was friendly with. According to Soper, “they were not particularly glad to see her.” She suffered a stroke in 1932, and passed away at age 69 on November 11, 1938. Only nine people attended her funeral at St. Luke’s Catholic Church in the Bronx.

In total, Mallon was officially responsible for infecting 53 people with typhoid—three of whom died—though there were likely many more that went unreported. While her commitment to good hygiene may have been lacking, the fact that she was so often treated like a pariah no doubt exacerbated her unwillingness to cooperate with doctors and other health officials. For many, including Mallon herself, it was simply difficult to believe that a perfectly healthy person who had never even been afflicted with a terrifying disease could somehow pass it on to dozens of others.

“It was to be Mary Mallon’s fate to clear away much of the mystery which surrounded the transmission of typhoid fever and to call attention to the fact that it was often persons rather than things who offered the proper explanation when the disease occurred in endemic, sporadic and epidemic form,” Soper wrote.

Mallon, however begrudgingly, charted a new path for scientists studying communicable diseases—and taught the rest of us just how important it is to wash our hands.

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