Ask Well: Is Rebounding Good Exercise?


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I’ve been reading a lot about rebounding as an excellent exercise for all ages. The benefits seem almost miraculous, but I don’t find any articles in Well about this form of exercise. Have you looked into it?


Many websites do tout almost miraculous benefits from jumping on a rebounder or, as it is also known, a minitrampoline, claiming that such workouts improve fitness, build bone, spur lymphatic drainage, fight depression, and goose the health of every cell in your body, since they supposedly experience beneficial G-force pressure during a workout.

These claims are unproven. Enthusiasts often cite a 1980 study by NASA scientists showing that rebounding required more effort than running while it was gentler on joints. More recent science disagrees. By most estimates, rebound exercise is, at best, aerobically mild, requiring less effort than bowling and about the same as playing croquet. Even competitive trampoline athletes get less of a workout per minute than most runners.

There also is little or no scientific evidence that rebounding benefits the lymph system, bones, mood or cellular health.

But rebounding does improve balance in older people. A study published in November in the Archives of Gerontology and Geriatrics found that older women were less wobbly after 12 weeks of gentle, supervised rebounding exercise, although women who completed standard balance training showed similar improvement.

Exercising on a trampoline, even a mini one, also has risks. Trampoline-related injuries send many people to emergency rooms or orthopedists every year,epidemiological studies show. Interestingly, in adults, trampoline injuries typically involve joint sprains, while small children tend to tumble off and require stitches.

The upshot: If you decide to use a rebounder, exercise caution, and if your primary goal is fitness, consider bowling, a safer activity that requires more physiological effort.

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Well: 4 Days, 11 Pounds


Credit Illustration by Ben Wiseman

This article appeared in the May 25, 2014 issue of The New York Times Magazine.

Losing weight is simple: Ingest fewer calories than your body burns. But how best to do that is unclear. Most experts advise small reductions in calories or increases in exercise to remove weight slowly and sensibly, but many people quit that type of program in the face of glacial progress. A new study, published in March in The Scandinavian Journal of Medicine & Science in Sports, suggests that minimal calories and maximal exercise can significantly reduce body fat in just four days — and the loss lasts for months. The catch, of course, is that those four days are pretty grueling.

Researchers in Spain and Sweden had 15 healthy but overweight Swedish men restrict their calories to about 360 a day, a reduction of approximately 1,800 calories. What calories they did ingest came in liquid form: Some men drank mostly sugary carbohydrates, others a high-protein drink. The men also exercised — a lot. Their days began with 45 minutes of cranking an arm-pedaling machine for an upper-body workout. Then, as a group, the men strolled for eight hours across the Swedish countryside, with only a 10-minute break every hour. They were allowed as much of a low-calorie, sports-type beverage as they wanted during their walks.

Most of the men “were surprised that it was easier than they thought it would be,” says José Calbet, a professor at the University of Las Palmas de Gran Canaria in Spain; he and his colleague Hans-Christer Holmberg, a professor at Mid Sweden University in Ostersund, led the study. Some of the subjects experienced “minor problems with pain in the joints” and blisters on their feet, according to Calbet, but none dropped out or complained of hunger.

After four days, the men had each lost almost 11 pounds, with nearly half of that coming from body fat; the rest of the loss came primarily from muscle mass. The researchers had anticipated that the high-protein drink would protect people against muscle-mass loss. In fact, the losses were the same, whether the men had been given sugar or protein.

More surprising, the men did not immediately put the weight back on after the study ended. “We thought they would overeat and regain the weight lost,” Dr. Calbet says. Instead, when the volunteers returned a month later, most had lost another two pounds of fat. And a year after the experiment, they were still down five pounds, mostly in lost body fat.

Dr. Calbet and his colleagues hope to study whether women respond similarly to men and whether repeated bouts of such a program might affect muscular health and appetite hormones.

But given the doleful statistics on weight loss — most people regain everything they lose dieting and more — these results are startling. They also, at the moment, are inexplicable. “The only explanation we can offer” for the sustained loss, Dr. Calbet says, is that the men were inspired by their hypercompressed success to change their lifestyles. The men moved more and ate less than before.

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Well: Why High-Impact Exercise Is Good for Your Bones


Credit Illustration by Ben Wiseman

This article appeared in the March 9, 2014 issue of The New York Times Magazine.

Bones should be jarred, for their own good. Past experiments have definitively established that subjecting bones to abrupt stress prompts them to add mass or at least reduces their loss of mass as people age. What has been in dispute, however, is how much force is needed to stimulate bone — and how to apply that force in daily life.

Recently researchers at the University of Bristol gathered male and female adolescents — the body accumulates bone mass rapidly at this time of life — and had them go about their daily routines while they wore activity monitors. The bone density of the volunteers’ hips was also measured.

A week later, the scientists reclaimed the monitors to check each teenager’s exposure to G forces­, a measure of impact. Those who experienced impacts of 4.2 G’s or greater — though these were infrequent — had notably sturdier hipbones. Additional work done by the same researchers showed that running a 10-minute mile or jumping up onto and down from a box at least 15 inches high was needed to produce forces that great. The significance of these findings is that people should probably run pretty fast or jump high to generate forces great enough to help build bone.

Unfortunately, few older adults are likely to be doing so. In follow-up experiments, the same researchers equipped 20 women older than 60 with activity monitors and ran them through an aerobics class, several brief and increasingly brisk walks and a session of stepping onto and off a foot-high box. None of the women reached the 4-G threshold ­— none, in fact, generated more than 2.1 G’s of force at any point during the various exercises.

The implications are somewhat concerning. Dr. Jon Tobias, a professor of rheumatology at the University of Bristol who led the experiments, says that while impacts that produce fewer than 4 G’s of force may help adults maintain bone mass — a possibility that he and his colleagues are exploring in ongoing experiments — it’s unclear what level of force below 4 G’s is needed.

So, Dr. Tobias says, young people and healthy adults should probably pound the ground, at least sometimes. Sprint. Jump off a box 15 inches or higher at your gym and jump back up. Hop in place. A study by other researchers published in January found that women between 25 and 50 who hopped at least 10 times twice a day, with 30 seconds between each hop, significantly increased their hipbone density after four months. Another group of subjects, who hopped 20 times daily, showed even greater gains.

Alas, a kind of Catch-22 confronts older individuals who have not been engaging in high-impact exercise: Their bodies and bones may not be capable of handling the types of activity most likely to improve bone health. Dr. Tobias and his colleagues hope to better understand what level of impact will benefit these people. In the meantime, anyone uncertain about the state of his or her bones should consult a physician before undertaking high-impact exercise (a caveat that also applies to those with a history of joint problems, including arthritis). For his part, Dr. Tobias says, “I plan to keep running until my joints wear out.”

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Well: For a 7-Minute Workout, Try Our App



Got seven minutes? We’ve got the app.

Today The New York Times is offering a free mobile app for the popular Scientific 7-Minute Workout and the new Advanced 7-Minute Workout.

The workouts, reported by Gretchen Reynolds, our Phys Ed columnist, can now be installed on your smartphone or tablet, or used on your desktop computer.

The app offers a step-by-step guide to both 7-minute workouts, offering animated illustrations of the exercises, as well as a timer and audio cues to help you get the most out of your seven minutes.

In the coming months, we’ll offer additional Well fitness apps to give you a full library of workout options using your smartphone, tablet or computer as a personal fitness guide. If you have suggestions or feedback about the new apps, feel free to post a comment below. iPhone and iPad app users can leave comments here.

How To Install



On an iOS device, open this link. Tap the “Bookmark” button, then “Add to Home Screen.” The app is then usable even if you don’t have an Internet connection.



On an Android device, use the Chrome browser to open this link. Then tap the “Menu” button, then “Add to Home Screen.” The app is then usable even if you don’t have an Internet connection.

To use on a desktop or other device, click here.

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Daylight Saving Time: Why Does It Exist? (It’s Not for Farming)

“Americans really do leave their homes when there is more sunlight at the end of the day,” said Michael Downing, a lecturer at Tufts University and the author of “Spring Forward: The Annual Madness of Daylight Saving Time.”

“We go to the parks, and we go to the mall, but we don’t walk there,” he said. “Daylight saving increases gasoline consumption.”

No one is more aware of that than gas stations, which is why the Association for Convenience and Fuel Retailing, a lobbying group for convenience stores, has pushed to start daylight saving time earlier in the year. In 2010, Jeff Miller, the group’s chairman at the time, said the industry had added an estimated $1 billion in annual sales since the organization lobbied to add a month to daylight saving in 1986.

“That’s tens of billions of dollars in sales since then,” he said in a news release.

Those in the leisure industry have also benefited, Mr. Downing said. For example, he said, the Chamber of Commerce has lobbied on behalf of retailers that sell gardening, home repair or sports equipment. Lobbyists from the golf industry estimated in 1986 that an extra month of daylight saving would be worth $200 million to $400 million.

Before lights were installed in professional stadiums, Major League Baseball had to end some games in ties because of darkness, and fans often felt robbed by such dissatisfying endings. In the two seasons after daylight saving began, the number of ties decreased to five from 22.

Who’s Opposed?

It might be surprising to find farmers in this category considering the common belief that they are the reason for daylight saving time.

“I don’t know how that ever became a myth, but it is the exact opposite,” Mr. Prerau said. He said daylight saving time actually disrupts farmers’ schedules.

Initially, farmers were the strongest lobby against the change. But since then, opposition has fragmented into much smaller interest groups, Mr. Downing said, including religious groups that schedule prayers around sunrise. Parents have also complained about having their children walk to school in the dark.

Some have argued it leads to an increase in traffic accidents. Mayor Bill de Blasio of New York warned drivers to be vigilant, calling the morning commute that will now be darker “a serious danger.”

And some anti-federalists are opposed to what they consider unnecessary government intervention. (Arizona and Hawaii are the only two states that have held out.)

Energy Savings

The idea was originally rooted in saving candle wax, not electricity.

Historians have traced the notion back to Benjamin Franklin, who realized he was sleeping through some daylight hours while visiting Paris in the 18th century. He suggested French officials shoot cannons at sunrise to jolt people out of bed, optimizing the amount of hours they spent awake when it’s light out. That way, they could cut down on using candles to light their homes while awake, Mr. Prerau said.

But the first idea to move the clock hands came from William Willett, who unsuccessfully proposed it to the British Parliament in 1908. Germany, however, seeking cost savings during World War I, heard the idea and enacted it in 1915. Three weeks later, the British followed, and other world powers were close behind, including the United States in 1918.

Reducing energy consumption is still often cited as a chief driver of daylight saving time, but experts can’t agree on whether that is actually a result. There have been many conflicting studies.

A Department of Energy report from 2008 found that the extended daylight saving time put in place in 2005 saved about 0.5 percent in total electricity use per day.

But Matthew Kotchen, a Yale economist, found a 1 percent increase in electricity use after Indiana introduced daylight saving statewide in 2006, estimating a cost of $9 million per year for consumers.

“The consequence for Indiana has been higher electricity bills and more pollution from power plants,” Mr. Kotchen wrote in Room for Debate.

Mr. Downing said the idea was originally based on having “an eight-hour economy,” but electricity demand is no longer based on sunrises and sunsets — not when there’s air conditioning.

“It has long been a cynical substitute for real energy policy,” he said. “It’s the ideal energy policy because it has no apparent direct cost to consumers, and it asks no one to consume less.”

Continue reading the main story

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