ORLANDO, Fla. – Human spaceflight to Mars could become a reality within the next 25 years, but not until some physiological problems are resolved, including an alarming loss of bone mass, fitness and muscle strength. Former astronaut James A. Pawelczyk, Ph.D. illuminated the issues in a keynote address today at the American College of Sports Medicine (ACSM) 10th-annual Health & Fitness Summit & Exposition in Orlando. Pawelczyk, a kinesiologist, served as payload specialist in 1998 for the last flight of the Spacelab science module. The mission, known as Neurolab, focused on how the nervous system responds to the challenges of spaceflight.

In his remarks, Pawelczyk reviewed the environments of deep space and the Martian surface, noting in particular the impacts they may have on humans. For example, gravity at Mars' surface is about 38 percent of that on Earth.  "With lower gravitational forces," he said, "bones decrease in mass and density." Also affected are muscles, the cardiovascular system, and immune functions. A recent NASA-funded study has found the human body's ability to fight off disease may be decreased by spaceflight.

"The rate at which we lose bone in space is 10-15 times greater than that of a post-menopausal woman," said Pawelczyk. "There's no evidence that bone loss ever slows (in space.) Further, it's not clear that space travelers will regain that bone on returning to gravity. Recent data suggests that not all people are recovering."

During a trip to Mars—lasting between 13 and 30 months—unchecked bone loss could make an astronaut's skeleton "the equivalent of a 100-year-old person," Pawelczyk warned. Bones weakened to such an extent would be highly susceptible to fractures, putting space travelers' health and the mission itself at risk.

In addition to bone loss, those planning for extended spaceflight are concerned about exercise capacity (cardiorespiratory fitness) and muscle strength. According to Pawelczyk, "With a trip to Mars, a third of exercise capacity will be lost, and about the same amount of muscle strength—that is, barring an intervention."

Such interventions are likely to include exercise, which astronauts long have practiced in spaceflight as well as in training and experiments. While Earth-based exercise is well known to build muscle, cardiorespiratory fitness and bone strength, scientists have not identified equivalent benefits in space. "Exercise alone has not been sufficient to prevent loss of bone, muscle strength and fitness capacity. More research is needed," said Pawelczyk.

One promising strategy involves combinations of exercise and drug therapy. "These haven't been tried in space," said Pawelczyk, "but have had some level of success in preserving bone in Earth-based research programs." Future experiments may team exercise with drugs commonly used to fight osteoporosis.

ACSM's Health & Fitness Summit & Exposition is going on now at The Buena Vista Palace at Walt Disney World. For more information on the event, or to speak with staff in the on-site media office, please call 407-938-6156 (through Friday, April 14, 2006).

The American College of Sports Medicine is the largest sports medicine and exercise science organization in the world. More than 20,000 International, National and Regional members are dedicated to promoting and integrating scientific research, education and practical applications of sports medicine and exercise science to maintain and enhance physical performance, fitness, health and quality of life.

ACSM would like to thank the following supporters of the 2006 Health & Fitness Summit & Expo: Amino Vital, Gatorade, The Centers for Disease Control and Prevention, Mars, New Lifestyles, PowerBar, Sport Beans, Lippincott Williams & Wilkins, 6th Dimension Devices, exel, NSF International, Suunto, Thera-Band, Viasys Healthcare, and Yamax.