Knee Brace Generates Electricity From Walking

Daily Science Journal (Feb. 9, 2008) — A new energy-capturing knee brace can generate enough electricity from walking to operate a portable GPS locator, a cell phone, a motorized prosthetic joint or an implanted neurotransmitter, research involving the University of Michigan shows.

The biomechanical energy harvester includes an aluminum chassis and generator mounted on a customized orthopaedic knee brace. The device weighs 3.5 lbs. (Credit: Greg Ehlers/Simon Fraser University)

The wearable mechanism works much like regenerative braking charges a battery in some hybrid vehicles, said Arthur Kuo, an associate professor of mechanical engineering at U-M and an author of the paper.*

Regenerative brakes collect the kinetic energy that would otherwise be dissipated as heat when a car slows down. This knee brace harvests the energy lost when a human brakes the knee after swinging the leg forward to take a step.

Kuo, who called the device "a cocktail-napkin idea," says knee joints are uniquely suited for this endeavor.

"There is power to be harvested from various places in the body, and you can use that to generate electricity. The knee is probably the best place," he said. "During walking, you dissipate energy in various places, when your foot hits the ground, for example. You have to make up for this by performing work with your muscles.

"The body is clever," Kuo said. "In a lot of places where it could be dissipating energy, it may actually be storing it and getting it back elastically. Your tendons act like springs. In many places, we're not sure whether the energy is really being dissipated or you're just storing it temporarily. We believe that when you're slowing down the knee at the end of swinging the leg, most of that energy normally is just wasted."

The scientists tested the knee brace on six men walking leisurely on a treadmill at 1.5 meters per second, or 2.2 miles per hour. They measured the subjects' respiration to determine how hard they were working. A control group wore the brace with the generator disengaged to measure how the weight of the 3.5-pound brace affected the wearer.

In the mode in which the brace is only activated while the knee is braking, the subjects required less than one watt of extra metabolic power for each watt of electricity they generated. A typical hand-crank generator, for comparison, takes an average of 6.4 watts of metabolic power to generate one watt of electricity because of inefficiencies of muscles and generators.

"We've demonstrated proof of concept," Kuo said. "The prototype device is bulky and heavy, and it does affect the wearer just to carry. But the energy generation part itself has very little effect on the wearer, whether it is turned on or not. We hope to improve the device so that it is easier to carry, and to retain the energy-harvesting capabilities."

A lighter version would be helpful to hikers or soldiers who don't have easy access to electricity. And the scientists say similar mechanisms could be built into prosthetic knees other implantable devices such as pacemakers or neurotransmitters that today require a battery, and periodic surgery to replace that battery.

"A future energy harvester might be implanted along with such a device and generate its own power from walking," Kuo said.

The paper "Biomechanical Energy Harvesting: Generating Electricity During Walking with Minimal User Effort" is published in the Feb. 8 issue of the journal Science. Authors include researchers from Simon Fraser University in Canada and the University of Pittsburgh, in addition to U-M.

Adapted from materials provided by University of Michigan.

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'Weight Training' Reduces Fat And Improve Metabolism In Mice

Daily Science Journal (Feb. 8, 2008) — Researchers from the Boston University School of Medicine (BUSM) have demonstrated that in mice, the use of barbells may be as important to losing weight and improving health as the use of running shoes. The discovery builds upon the fact that skeletal muscle consists of two types of fibers. Endurance training such as running increases the amount of type I muscle fibers, while resistance training such as weightlifting increases type II muscle fibers. Using a mouse genetic model, BUSM researchers demonstrated that an increase in type II muscle mass can reduce body fat which in turn reduces overall body mass and improves metabolic parameters such as insulin resistance. These studies indicate that weight bearing exercise, in addition to endurance training, may benefit overweight people.

Weight-lifting. "We've shown that type II muscle does more than allow you to pick up heavy objects," said Kenneth Walsh of Boston University School of Medicine. "It is also important in controlling whole-body metabolism." (Credit: iStockphoto/Sean Locke)

Researchers used a genetic trick in obese mice that caused the mice's muscles to bulk up as though they had been lifting weights. The researchers found that the "genetically reprogrammed" mice lost fat and showed other signs of metabolic improvement throughout the body. What's more, those benefits were seen even though the mice continued eating a diet high in both fat and sugar and didn't increase their physical activity at all.

The researchers genetically engineered a mouse, called the MyoMouse, to grow type II fibers by activating a muscle growth-regulating gene. The gene, called Akt1, was engineered in such a way that it could be turned on and off at will by researchers. Even without exercise, activating the gene made the MyoMouse physically stronger. When the gene was de-activated, the mouse returned to its original strength. While stronger and faster than a regular mouse, the MyoMouse did not run with as much endurance on a treadmill, a finding that is consistent with the growth of type II rather than type I muscle. These findings demonstrate that the mouse was genetically programmed to have the characteristics of a lean and powerful sprinter rather than those of a gaunt marathon runner.

"We've shown that type II muscle does more than allow you to pick up heavy objects," said Kenneth Walsh of Boston University School of Medicine. "It is also important in controlling whole-body metabolism."

In the study, the Akt1 gene was turned off and the MyoMice were fed a high fat/high sugar diet with a similar caloric composition as a meal from a fast food restaurant. Over an eight-week period, the mice became obese and insulin resistant and developed fatty acid deposits in their liver, a condition referred to as hepatic steatosis or fatty liver disease.

The researchers then activated the Akt1 gene in the animals which led to the growth of type II muscle fibers. "Remarkably, type II muscle growth was associated with an overall reduction in body mass, due to a large decrease in fat mass. In addition, blood tests showed that these mice became metabolically normal and their fatty liver disease rapidly resolved," said senior author Kenneth Walsh, PhD, a professor of medicine and head of Molecular Cardiology at the Whitaker Cardiovascular Institute at BUSM.

The beneficial changes occurred despite the fact that the mice continued to eat the same high-calorie diet and did not display any increase in physical activity. "This work shows that type II muscle just doesn't allow you to pick up heavy objects, it is also important in controlling whole body metabolism," added Walsh.

Further analysis found that the mice burned fat because of changes in the physiology and gene expression of their fat and liver cells. "Thus, it appears that the increase in type II muscle fiber orchestrates changes in the body through its ability to communicate with these other tissues," he said.

These findings indicate that type II muscle has a previously unappreciated role in regulating whole body metabolism through its ability to alter the metabolic properties of remote tissues. These data also suggest that strength training, in addition to the widely-prescribed therapy of endurance training, may be of particular benefit to overweight individuals

Finally, these findings may be relevant for understanding aspects of the aging process. "Beyond the age of thirty, humans lose approximately 6 lbs of muscle mass per decade. Surprisingly, aging individuals predominantly lose type II muscle. Thus a 50 year old may be relatively good at playing tennis or jogging because type I muscle is preserved, but a measurement of grip strength or core body strength could show appreciable declines," explained Walsh. Therefore, this new study suggests that the loss of type II muscle contributes to the development of obesity and diabetes as we age.

The BUSM researchers suspect that the beneficial effects of muscle growth seen in the MyoMouse are mediated through the production and secretion of a variety of signaling factors. Walsh and his colleagues are currently identifying the novel proteins in muscle that communicate with other tissues. These new proteins, referred to as "myokines" from the Greek words "muscle" and "motion," may represent new targets for therapies that mimic the benefits of weight training for the treatment of obesity and diabetes as well as muscle wasting disorders.

"The work of [Walsh and his colleagues] reveals the intricate interplay between diet, energy balance, and the function/morphology of diverse tissue systems such as skeletal muscle and liver," said Brooke Harrison and Leslie Leinwand of the University of Colorado at Boulder in a commentary in the journal Cell Metabolism. "These findings indicate that interventions designed to increase skeletal muscle mass in at-risk human populations may prove to be critical weapons in the fight against obesity and obesity-related comorbidities including diabetes, heart disease, stroke, hypertension, and cancer."

The study appears in the February 6th issue of Cell Metabolism. The researchers include Yasuhiro Izumiya, Teresa Hopkins, Carl Morris, Kaori Sato, Ling Zeng, Jason Viereck, James A. Hamilton, Noriyuki Ouchi, Nathan K. LeBrasseur, and Kenneth Walsh, of Boston University School of Medicine, Boston, MA.

Adapted from materials provided by Boston University, via EurekAlert!, a service of AAAS.

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Plastic Bottles Release Potentially Harmful Chemicals (Bisphenol A) After Contact With Hot Liquids

Daily Science Journal (Feb. 5, 2008) — When it comes to Bisphenol A (BPA) exposure from polycarbonate plastic bottles, it's not whether the container is new or old but the liquid's temperature that has the most impact on how much BPA is released, according to University of Cincinnati (UC) scientists.

Scott Belcher, PhD, tested polycarbonate plastic bottles like these for Bisphenol A. (Credit: Image courtesy of University of Cincinnati)

Scott Belcher, PhD, and his team found when the same new and used polycarbonate drinking bottles were exposed to boiling hot water, BPA, an environmental estrogen, was released 55 times more rapidly than before exposure to hot water.

"Previous studies have shown that if you repeatedly scrub, dish-wash and boil polycarbonate baby bottles, they release BPA. That tells us that BPA can migrate from various polycarbonate plastics," explains Belcher, UC associate professor of pharmacology and cell biophysics and corresponding study author. "But we wanted to know if 'normal' use caused increased release from something that we all use, and to identify what was the most important factor that impacts release."

"Inspired by questions from the climbing community, we went directly to tests based on how consumers use these plastic water bottles and showed that the only big difference in exposure levels revolved around liquid temperature: Bottles used for up to nine years released the same amount of BPA as new bottles."

BPA is one of many man-made chemicals classified as endocrine disruptors, which alter the function of the endocrine system by mimicking the role of the body's natural hormones. Hormones are secreted through endocrine glands and serve different functions throughout the body.

The chemical--which is widely used in products such as reusable water bottles, food can linings, water pipes and dental sealants--has been shown to affect reproduction and brain development in animal studies.

"There is a large body of scientific evidence demonstrating the harmful effects of very small amounts of BPA in laboratory and animal studies, but little clinical evidence related to humans," explains Belcher. "There is a very strong suspicion in the scientific community, however, that this chemical has harmful effects on humans."

Belcher's team analyzed used polycarbonate water bottles from a local climbing gym and purchased new bottles of the same brand from an outdoor retail supplier.

All bottles were subjected to seven days of testing designed to simulate normal usage during backpacking, mountaineering and other outdoor adventure activities.

The UC researchers found that the amount of BPA released from new and used polycarbonate drinking bottles was the same -- both in quantity and speed of release -- into cool or temperate water.

However, drastically higher levels of BPA were released once the bottles were briefly exposed to boiling water.

"Compared to the rate of release from the same bottle, the speed of release was 15 to 55 times faster," explains Belcher.

Prior to boiling water exposure, the rate of release from individual bottles ranged from 0.2 to 0.8 nanograms per hour. After exposure, rates increased to 8 to 32 nanograms per hour.

Belcher stresses that it is still unclear what level of BPA is harmful to humans. He urges consumers to think about how cumulative environmental exposures might harm their health.

"BPA is just one of many estrogen-like chemicals people are exposed to, and scientists are still trying to figure out how these endocrine disruptors--including natural phyto-estrogens from soy which are often considered healthy--collectively impact human health," he says. "But a growing body of scientific evidence suggests it might be at the cost of your health."

The UC team reports its findings in the Jan. 30, 2008 issue of the journal Toxicology Letters. UC graduate student Hoa Le and summer undergraduate research fellows Emily Carlson and Jason Chua also participated in this study, which was funded by a National Institute of Environmental Health Sciences grant.

Adapted from materials provided by University of Cincinnati.

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