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t m c » p u l s e | n o v e m b e r 2 0 1 5 23 a bike ride and somewhere between the Mississippi and Lake Michigan, decided to join the U.S. Army. He simultaneously completed a two-year aerospace medicine residency and musculoskeletal ultrasound fellowship along the way. With three tours under his belt and an Army Reserves lanyard around his neck, Scheuring, along with McCulloch, provides a unique expertise to a small population of individuals who, as far as jobs go, work in a field about as specialized as you can get. "The competition is fierce," McCulloch said, when asked about the astronaut selection process. "Screening is based on physical fitness and health, but they also require special skills and abilities that are uncommon. A lot of our astronauts are active or former military, many of them played col- lege sports, and they understand the importance of teamwork and discipline. By the time they actually go into space, most of them are in their mid-40s, so we're working with what is akin to an aging athlete population that is prone to having some musculoskeletal inju- ries as a result of their age, the training requirements, and the fact that the job is just physically demanding." By providing an onsite clinic, the astronauts are able to focus on training and rehabilitation rather than traveling to and from the Texas Medical Center for specialized orthopedic care. "Before the clinic, astronauts would have to go see a doctor, get a referral, go see another doctor locally or in the medical center, get an MRI ordered, and then follow up again—that's a big interruption to their already packed schedules," McCulloch explained. "With Houston Methodist being at the Space Center weekly, we're not only picking up on issues earlier and therefore preventing more injuries, but should anyone need an orthopedic surgery, we've streamlined the process so time outside the Space Center is minimal. The stakes are just higher for astronauts—they don't have weeks or months to deal with an injury when they have a launch date set." McCulloch added that the program is beneficial to his fellows as well because it provides them exposure to practices unique to aerospace medi- cine, like the use of musculoskeletal ultrasound in place of X-rays, MRIs and CTs. Considered the stethoscope of orthopedics, it is currently the only imaging modality available in orbit and can be used for diagnostic purposes or to guide procedures or injections. Astronauts are trained to use the machines, and flight surgeons are proficient in reading and interpreting the images in real-time back on Earth— telemedicine at its finest. Of all the injuries common to the astronaut corps—between knee com- plaints, back pain and herniated discs, which may or may not be related to the two to six centimeters you grow in space—shoulder issues eclipse them all. This is partly explained by the fact that arms and shoulders replace the legs as the primary mode of mobility—in microgravity, one doesn't so much walk as pull or propel. Likewise, astronauts are forced to put pressure on their shoulders by strapping them down for routine activities such as sleep or exercise. "It's very difficult trying to come up with a training program for astronauts in space to help them maintain their bone density and muscle mass, which inevitably decreases in the absence of gravity," McCulloch said. "You can't lift weights because they don't weigh anything. Instead, we secure crewmem- bers to a treadmill with bungee cords that attach around their waist and a harness that goes over their shoulders, but having 40 percent of your body weight pulling through your shoulders while you're running is not exactly a natural phenomenon." Perhaps the biggest bearer of blame, however, is the spacesuit itself. Although weightless in microgravity and only worn for missions outside the shuttle, astronauts log hundreds of hours of training in the suit in prepa- ration for each trip. "We do a lot of training in NASA's Neutral Buoyancy Laboratory, which holds the world's largest swimming pool. The astronauts essentially go scuba diving in the spacesuit and practice their mission on a life-sized mock-up of the Space Station, which sits at the bottom," McCulloch said. "Unfortunately, it is not a perfect simu- lator for true weightlessness." Neutral buoyancy is more accu- rately described as "hovering." Because microgravity could not be replicated here on Earth at the scale necessary for NASA's rigorous extravehicular activity training requirements, the sensation of half-floating, half-sinking would have to do. The disadvantage, of course, is that the astronauts still feel their weight and the weight of the suit—all 300 lbs. of it. "They may be down there for hours working with tools and moving in awkward positions, and the spacesuit restricts some of their motion, so often they'll be sore in their shoulders after doing these repetitive tasks over long periods of time," McCulloch said. While the pesky issue of gravity on Earth can't exactly be resolved, McCulloch, Scheuring and a team at NASA have recommended several modifications to the training process to help astronauts reduce injuries while working within the constraints of the EMU. Moving forward, NASA has recruited the duo to advise its team of engineers and designers as they build the next generation of spacesuits. By evaluating the musculoskeletal physiology of suited-up astronauts engaged in activity, they hope to iden- tify key features that will help minimize risk and maximize performance. "We're looking at the factors that we believe cause injuries in some astro- nauts so that we can ensure we don't engineer those into the new spacesuit," Scheuring explained. "The problem is, the spacesuit is very complicated, so you don't want to fix a problem with the shoulder but then cause a different problem with the elbow or the wrist or the lower back. It's an intricate process." Although the new suits will almost certainly allow for improved range of motion in the shoulders and neck, NASA doesn't expect to unveil a sleek, ergonomically pleasing design anytime soon. Because the primary requirement of the spacesuit is to provide a pressur- ized volume compartment to protect the oxygen-loving, temperate-adapted crewmember while exploring non-Earth environments, the EMU's trusted bulky layers are here to stay. "You have to think of it as a per- sonalized spacecraft," Scheuring said. "Ultimately, a few consolations in design have to be made for overall crew safety." We have a real source of national pride here in Houston at the Johnson Space Center, and we have another one here in the Texas Medical Center, and the ability for us to contribute mutually in this regard is imperative for us as a leading health care institu- tion and important for us as Americans. — PATRICK McCULLOCH, M.D. Orthopedic Surgeon at Houston Methodist Hospital Rick Scheuring, D.O., flight surgeon for NASA and the Johnson Space Center, and Patrick McCulloch, M.D., orthopedic surgeon at Houston Methodist Hospital, walk the halls at NASA after a recent Wednesday clinic.