Low magnitude high frequency vibrations applied to the foot through the pedal of a human powered artificial gravity (HPAG) cycle

Abstract

Astronauts are exposed to hazards unique to space travel. These hazards include radiation exposure and adaptation of the human body to the microgravity environment. For lunar and low earth orbital missions, the exposure period is typically less than six months and return to Earth is less than two weeks away. For travel beyond the Earth's moon, the microgravity exposure time will increase from months to years and return time will increase from weeks to months. Current countermeasures employ impact and high force loading to maintain bone health. An astronaut runs on a treadmill to impact load the weight bearing components of the musculoskeletal system. Elastic bands provide the "down" force for the astronaut while running. For high force loading, the astronaut performs a specified regimen of weight lifting exercises using resistive devices. The resistive devices provide a load in microgravity similar to that of free weights on Earth. These countermeasures have been beneficial in slowing bone adaptation, but have not stopped it. The imperceptible muscle contractions required for posture maintenance may be the absent load that the skeletal system requires to maintain bone health. Unlike the muscles that are required for impact and high force loading, the postural muscles work continuously to keep humans balanced and upright in a gravity environment.

(cont.) Jumping, running and even sitting require posture maintenance. Studies have shown that low magnitude loads applied at a high frequency to the weight bearing bones have not only maintained the bone mineral density, but also more importantly, maintained the structure of the bones. This thesis demonstrates the design of a vibrating pedal that delivers a perceptible, low magnitude load at a high frequency ([approx.]30 Hz) to the foot. This design required no external power and was implemented on a Human Powered Artificial Gravity (HPAG) cycle. A device similar to the vibrating pedal device created for this research could benefit society by providing an effective therapy against the disease of osteoporosis. A vibrating pedal could easily be mounted on a stationary cycle, possibly even standard bicycle, and provide a beneficial therapy to the user.