The rocket scientists at NASA have devised some high-tech “weights” for space workouts:
In the first-ever analysis of muscles from International Space Station astronauts, Trappe’s team found that six months in near zero-gravity had produced a 15 percent loss in muscle volume and 25 percent loss in strength.
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However, the exercise of space station astronauts is limited to the machines they’re given. Though a treadmill and stationary bicycle work fine, they’re intended primarily for aerobic conditioning. Muscle strength is the responsibility of the Interim Resistance Exercise Device, or iRED — and, with a maximum resistance of just 300 pounds, it can’t do the job.“Astronauts are working out hard, but the loading characteristics aren’t there,” said Trappe. “They’re losing more muscle mass than they should be.”
Simply maintaining muscle mass in space, said Trappe, requires a high-weight, low-repetition workout. The aRED is the first piece of NASA exercise equipment to meet this need. Providing resistance in each exercise are two piston-driven vacuum cylinders that are a bit like oversize bicycle pumps. Resistance increases as a piston is pulled in or out, so weights are set by adjusting the length of a mechanical arm that attaches pistons to lift bar.
Attached to the pistons is a flywheel, explained NASA astronaut strength conditioning and rehabilitation specialist Jim Loehr. Pushing the pistons out sets the flywheels spinning. That rotation, combined with vacuum pressure, provides a counter force against direction reversal so that a leg press in space requires effort as the weight is returned to its starting position, just as it does on Earth.
“ARED was designed to provide a constant force throughout the range of motion,” said Loehr, mimicking the physiological gold standard of free weight resistance. In contrast, the iRED was a 21st century version of a Bowflex machine, with unidirectional resistance provided by an ingenious arrangement of rubber bands that provide an “ascending force curve that doesn’t match traditional free weights,” and can lose strength over time.
For some exercises, like squats, a person needs to lift twice as much weight in space to get the same result as on Earth. So iRED’s maximum weight of 300 pounds translates to just 150 pounds squatted on Earth. Maintaining leg strength becomes extremely difficult with that amount of weight. And it’s the legs, accustomed to constantly supporting our bulks against Earth gravity, that weaken first in space. ARED’s maximum load of 600 pounds means astronauts can squat the equivalent of 300 pounds on Earth, which should be enough to keep their legs in shape.
Another problem with a Bowflex-style apparatus, said Trappe, is safety. “They have all these rubber cords and things attached to it that could snap,” he said, explaining that people fail to appreciate the extraordinary demands placed upon exercise machines in space.
Relying on pistons and fly wheels sounds less like a requirement and more like an interesting problem for the techies to solve.
I find it particularly amusing that the iRED is considered flawed because its ascending force curve doesn’t match free weights’ flat force curve, when earth-bound powerlifters now rely on elastic bands and metal chains attached to their barbells in order to attain just such an ascending force curve. The human body can handle more weight at the top of a squat or bench press than at the bottom. (And the specialized lifting suits allowed in powerlifting help more at the bottom than at the top.)
Anyway, with “just” 300 pounds of resistance and no body weight, a decent trainer would recommend some variation on split squats or true one-legged squats. But I don’t suppose they have a whole lot of trainers there at NASA.