Low-gravity training machine

A new CU-Boulder study of a space-age, low-gravity training machine led by Associate Professor Rodger Kram, shows the machine significantly reduced impacts on muscles and joints of study subjects.
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,â€� 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.â€� 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 â€" the equivalent of a seven-minute mile â€" decreased the “peakâ€� 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.                           - SD