August 14, 2012 | 1
How sports like gymnastics might evolve in the low gravity environments of future space colonies is a topic that resurfaces every now and then, particularly during the Olympic Games. With space tourism on the horizon and companies, such as Bigelow Aerospace, discussing a lunar setting for an off-world hotel, the Moon beckons as a tempting locale for humanity’s first space Olympics. Advantages of the Moon include its surface material, craters and accessible caves, and an equatorial surface gravity of 1.622 meters/sec2 –about 1/6th that of Earth. Together, these features would enable the construction of pressurized, radiation-shielded habitats with ample floor space and high ceilings.
In such a shirtsleeve, 1/6th G environment, the biomechanical parameters on lunar visitors will be very different from those experienced by the twelve Apollo astronauts who bunny hopped about in pressure suits and portable life support systems (PLSS, pronounced “pliss”). While an astronaut felt much lighter and bouncier than on Earth, despite the suit and PLSS doubling his mass, flexibility was markedly reduced, making somersaults dangerous, if not impossible.
But what about an event with less flight, such as pommel horse? This too would be challenging in a Moon suit, but could be set up in a shirtsleeve structure, even an early, prefabricated one, since it does not require a large room. “Bring a pair of portable pommels, if NASA picks you to go the Moon some day,” a gymnastics coach joked to me when I was about eighteen. “You’ll probably do a Bailey.” An old name for one circle swung over a single pommel, a Bailey is not something you saw last week in the Olympics, because it is too easy for those guys and would not add to the starting value. But it requires more leaning than circling between the two pommels, and more strength, or better technique.
Or less gravity. Arriving on the Moon, lunar tourists would enjoy strength to body weight ratios roughly six times what they experience on Earth, assuming they have not deconditioned by spending several weeks in weightlessness prior to arrival. This would have a profound impact on those gymnastics apparatus that are dominated by pushing and pulling –pommel horse, parallel bars, high bar, and still rings for men, and uneven bars for women. On these events, people of average strength might perform skills that on Earth require super strength, like a Maltese on rings, in which the gymnast suspends himself horizontally with arms in the same plane as his torso. At the same time, today’s Olympic gymnasts would invent and perfect new feats that are impossible in the gravitational pull that we feel at the surface of Earth.
One possible new family of skills that seems plausible to me is release moves from rings. Gymnastics is evolving so quickly that, who knows, maybe we’ll see a gymnast on Earth release from rings and re-catch after a somersault, but I’m not sure that it’s physically possible. On high bar and uneven bars, a gymnast can generate enough upward acceleration against Earth’s 9.8 meters/sec2 so as to twist, fly over the bar, or complete one or two somersaults, then catch the bar before he or she is too low. In a giant swing on rings, however, most of the energy is expended just getting the gymnast back up to the handstand. Moreover, the forces imparted on the shoulder joint are much higher when swinging from handstand to handstand on rings compared with a bar. Thus, while there is talk (and even some Youtube video footage) of gymnasts training release moves on rings, it seems unlikely that anyone will ever throw such a move in competition on Earth. On the Moon, though, it is certainly on the agenda, along with all sorts of one-arm tricks that may be waiting to be named for kindergarteners bouncing around some gyms in some corner of our planet today.
As for dismounts from pushing and pulling apparatus, people will have more air time than on Earth, opening the possibility for more somersaults and more twists in the air before landing. This raises the issue of injury. Although landing will be softer on the Moon, if coming down from the same height as on Earth, dismounts from bars (high, parallel, and uneven) will send the gymnast upward first, much higher as compared with Earth. Even from still rings, dismounts will occur with significant upward acceleration. Osteoporosis (which increases the fracture risk) is not really an issue, since we are talking about healthy people arriving fresh from Earth without weightless deconditioning, but disruption of otolith and proprioceptive sensors may be an issue in lunar gravity. Factor in four somersaults, instead of two, which means less room for error, and landing is probably less safe than on Earth, not more.
This brings us to the tumbling events: floor exercise, vault, and balance beam. Once airborne, the issues for the gymnast are similar to those we’ve discussed with respect to dismounts from the hanging and pushing events. Leave the floor, or the springboard, or the beam with the same force that you do on Earth, you go higher, with more air time, enabling more flips and twists. But regardless of how high you go, you come down with the same force with which you went up, a basic law of Newtonian physics that belies common myth about falling on the Moon. Thus, as with dismounts from other apparatus, the potential for injury is there, if one expects a landing to be softer than it really will be.
Getting into the air is another matter, and may not translate easily from a 1 G to a 1/6th G environment. On floor exercise and vault, running plays an important role in generating both height and rotation, but trying to run at 1/6th your usual weight sends you bouncing in the air, like being suspended from the ceiling with bungee while running on a trampoline. Power for a back rotating tumbling move comes from a round-off back handspring, which translates the forward velocity of the run into rotation and upward acceleration. This would have to be adjusted significantly on the Moon and fine tuned. It might end up looking similar to power strip tumbling on Earth. In this sport, tumblers after a trick often are thrown too high for an immediate back handspring, so they do a whipback, then adjust the angle to get their hands down the next time, since blocking with hands and snapping down launches you better than simply bouncing with just your feet.
On vault, upward velocity from the springboard, then from the vaulting table depends largely on speed. Like skimming a rock on water, the gymnast must hit the board with high velocity rather than sailing up and coming straight down. Yurchenko style vaults, in which the gymnast hits the board backward after a round-off, have somewhat different mechanics, but the basic idea is the same in terms of the run and speed. As with floor exercise, bunny hop running, as we saw from Apollo astronauts, will not do the trick.
On the balance beam, running is not the issue, but as with floor and vault, momentum for handsprings and somersaults that one might expect will be delivered in a linear direction might send the gymnast a lot higher than she wants to go. But as with the other events, the change in gravitational environment that makes things more difficult potentially can lead to amazing innovations –both in skills and apparatus– that we cannot begin to imagine.
Images: Iordan Iovtchev at London 2012 Olympics
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