G-Trainer: Low-gravity training machine reduces joint and muscle discomfort

A University of Colorado at Boulder study of a space-age, low-gravity training machine used by several 2008 Olympic runners showed it reduced impacts on muscles and joints by nearly half when subjects ran at the equivalent of 50 percent of their body weight.

The new study has implications for both competitive runners rehabilitating from injuries and for ordinary people returning from knee and hip surgeries, according to Associate Professor Rodger Kram of CU-Boulder’s integrative physiology department.

Known as the “G-Trainer,” the machine consists of a treadmill surrounded by an inflatable plastic chamber that encases the lower body of the runner, said Kram. Air pumped into the chamber increases the pressure and effectively reduces the weight of runners, who are sealed in the machine at the waist in a donut-shaped device with a special zipper and “literally lifted up by their padded neoprene shorts,” he said.

Published in the August issue of the Journal of Applied Biomechanics, the study is the first to quantify the effects of running in the G-Trainer, built by Alter-G Inc. of Menlo Park, Calif., using technology developed at NASA’s Ames Research Center in California. The paper was authored by Kram and former CU-Boulder doctoral student Alena Grabowski, now a postdoctoral researcher at the Massachusetts Institute of Technology.

Although G-Trainers have been used in some sports clinics and college and professional sports training rooms since 2006, the new study is the first scientific analysis of the device as a training tool for running, said Grabowski.

“The idea was to measure which levels of weight support and speeds give us the best combination of aerobic workout while reducing the impact on joints,” said Kram. “We showed that a person can run faster in the G-Trainer at a lower weight and still get substantial aerobic benefits while maintaining good neuromuscular coordination.”

The results indicated a subject running at the equivalent of half their weight in the G-Trainer at about 10 feet per second, for example — the equivalent of a seven-minute mile — decreased the “peak” force resulting from heel impact by 44 percent, said Grabowski. That is important, she said, because each foot impact at high speed can jar the body with a force equal to twice a runner’s weight.

Several former CU track athletes participating in the 2008 Olympics in Beijing have used the machine, said Kram. Alumna Kara Goucher, who will be running the 5,000- and 10,000-meter races in Beijing, has used the one in Kram’s CU-Boulder lab and one in Eugene, Ore., for rehabilitation, and former CU All-American and Olympic marathoner Dathan Ritzenhein also uses a G-Trainer in his home in Oregon. Other current CU track athletes who have been injured have tried the machine in Kram’s lab and found it helpful to maintain their fitness as they recovered, Kram said.

For the study, the researchers retrofitted the G-Trainer with a force-measuring treadmill invented by Kram’s team that charts vertical and horizontal stress load on each foot during locomotion, measuring the variation of biomechanical forces on the legs during running. Ten subjects each ran at three different speeds at various reduced weights, with each run lasting seven minutes. The researchers also measured oxygen consumption during each test, Kram said.

Grabowski likened the effect of the G-Trainer on a runner to pressurized air pushing on the cork of a bottle. “If you can decrease the intensity of these peak forces during running, then you probably will decrease the risk of injury to the runner.”

The G-Trainer is a spinoff of technology originally developed by Rob Whalen, who conceived the idea while working at NASA Ames as a National Research Council fellow to help astronauts maintain fitness during prolonged space flight. While the NASA technology was designed to effectively increase the weight of the astronauts to stem muscle atrophy and bone loss in low-gravity conditions, the G-Trainer reverses the process, said Grabowski.

In the past, sports trainers and researchers have used climbing harnesses over treadmills or flotation devices in deep-water swimming pools to help support the weight of subjects, said Kram. Harnesses are cumbersome, while pool exercises don’t provide sufficient aerobic stimulation and biomechanical loading on the legs, he said.

Marathon world-record holder Paula Radcliffe of Great Britain is currently using a G-Trainer in her high-altitude training base in Font-Remeu, France. Radcliffe is trying to stay in top running shape while recovering from a stress fracture in her femur in time for the 2008 Olympic women’s marathon on Aug. 17, according to the London Telegraph.

Kram and Grabowski have begun a follow-up study of walking using the G-Trainer. By studying subjects walking at various weights and speeds in the machine, the researchers should be able to quantify its effectiveness as a rehabilitation device for people recovering from surgeries, stress fractures and other lower body injuries, Kram said.

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Article adapted by MD Sports from original press release.
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Contact: Rodger Kram
University of Colorado at Boulder

10 Steps To Combat Low Back Pain

To celebrate Allied Health Professions Week, the National Athletic Trainers’ Association has prepared a 10-step guide that people of all ages can use to reduce body stress, prevent back pain and thereby improve quality of life – especially with holiday plans and travel just around the corner. Along with the season comes the lifting of heavy suitcases and holiday gifts that can put additional pressure on the back. NATA represents certified athletic trainers who are among the more than 80 professions being honored during Allied Health Professions Week (Nov. 4-10, 2007).

“The human body is an incredible machine that adapts to the stresses we give it every day,” said certified athletic trainer Darrell Barnes, LAT, ATC, CSCS, performance center coordinator, St. Vincent Sports Performance Center in Indianapolis, Ind. “Stresses such as poor posture, unusual movement or activities or even a sedentary lifestyle can lead to poor mechanics and pain. Disability from back pain is second only to the common cold as a cause of lost work time.”

According to the Arthritis Foundation, back pain affects 80 percent of the adult population at some point in their lives. In fact, back pain, limited mobility and stiffness end up costing American consumers $24 billion in treatment costs annually.

Following are recommendations to prevent and reduce back pain now and year-round:

1. Identify negative stresses that may be exacerbated by the holidays – Everybody has physical limitations that can lead to body imbalances, so it’s important to identify problematic areas and correct these imbalances. Look at your sitting/standing posture. Do you complain that your muscles “feel tight” or weak? Do you use poor mechanics when lifting heavy items? Are you putting unusual stress on the back with certain activities and lifting during the holiday season? Learning correct lifting techniques and strengthening your back can help to alleviate pain. Use a luggage cart or lighten your load when lifting heavy packages or luggage.

2. Make yourself mobile – Poor posture and muscle stiffness decrease the body’s ability to move freely, which can lead to injury or pain. There are many ways to increase mobility including daily stretches or activities that increase flexibility and get the body moving in different directions. Try yoga, tai chi, swimming or pilates to keep you limber.

3. Increase strength – It’s important to get strong to improve overall balance and flexibility to reduce stress on the back. Exercises should involve the whole body, especially the core muscles of the stomach, back, hips and pelvis. At the same time, strengthening of the legs and shoulders can help you more easily squat, lift and carry even heavy items without overworking or injuring your back.

4. Add aerobic exercise – Physical activities like walking, swimming and running for at least 20 minutes three times a week increases muscular endurance and cardiovascular fitness. Aerobic activities also improve blood flow to the spine and help decrease daily stress.

5. Pay attention to posture – Try not to sit or drive for long periods of time. Get up every 15 to 30 minutes and move around or stretch to increase your mobility. When seated always remember to keep your hips and knees at right angles to one another and find a chair with adequate lumbar (lower back) support.

6. Stand up straight – When engaged in activities while standing, be sure to stand with your head up, shoulders straight, chest forward and stomach tight. Avoid standing in the same position for too long, though, and use your legs – rather than your back – when pushing or pulling heavy doors and other items.

7. Use proper lifting mechanics – When lifting objects from a position below your waist, stand with a wide stance and a slight bend at your hips and knees. Tighten your stomach as you lift and keep your back as flat as possible – do not arch or bend. When carrying heavy objects, keep them as close to your body as you can. Avoid carrying objects on only one side of your body.

8. Get a good night’s sleep – Select a firm mattress and box spring that does not sag. Try to sleep in a position that allows you to maintain the natural curve in your back.

9. Warm-up before physical activity – Engage in a low impact activity prior to playing sports or exercising. Increasing muscle temperature and mobility will decrease the chance of injury.

10. Improve your healthy lifestyle – Obesity and smoking have been found to increase the incidence of back pain. Taking steps to improve your health will decrease the chance of back pain and improve your overall quality of life.

Barnes also urges people to always listen to their bodies: “If you are participating in any fitness routines or general activity and feel any twinges of back pain, you should stop immediately and consult your physician. Identifying the cause of the pain and treating it safely and appropriately will help you gain back mobility and range of motion and feel your physical best.”

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Article adapted by MD Only Weblog from original press release.
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Contact: Robin Waxenberg 
National Athletic Trainers’ Association

About the National Athletic Trainers’ Association (NATA)

Athletic trainers are unique health care providers who specialize in the prevention, assessment, treatment and rehabilitation of injuries and illnesses. The National Athletic Trainers’ Association represents and supports 30,000 members of the athletic training profession through education and research. Only 42 percent of high schools have access to athletic trainers. NATA advocates for equal access to athletic trainers for athletes and patients of all ages, and supports H.R. 1846.