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Advanced Resistive Exercise Device

ISS-44 Kjell Lindgren exercises using the Advanced Resistive Exercise Device

The Advanced Resistive Exercise Device (aRED) is an exercise machine for crew members in extensive space flights. It is designed to provide users with the ability to maintain muscle mass and strength in addition to sustaining their bone density and regulating nutrient intake. It employs several piston-driven vacuum cylinders to simulate free-weight exercises under normal gravity with the help of a connected adjustable resistance flywheel system.

It was designed by NASA to replace a multitude of exercise equipment which were required to allow astronauts to maintain optimal muscle mass and bone density in near zero-gravity conditions. It holds a potential secondary function as a replacement exercise machine on Earth as well, since it was designed to replace and simulate multiple currently existing exercise machines. This allows it to be used in a typical gym environment, where it would allow more than one muscle group to be worked on from an individual device, creating room in the gym for more specialised, muscle-group focused equipment. It was designed to be a relatively simple albeit robust device, providing the user with three primary resistive training exercises and fifteen secondary muscle exercises to ensure tension on major muscle groups and maintenance of bone density.

Development

The Advanced Resistive Exercise Device was designed to solve the problem of muscle mass dissipation during lengthy excursions on the International Space Station (ISS). Prototypes went through a rigorous testing phase to ensure that the new machine would rectify all the recently discovered problems regarding the first iteration of the exercise device on the International Space Station.

Numerous exercise devices currently exist on the market, with a prodigious amount of the machines designed to work under normal gravity (Earth's gravitational field). This refers to the exercise devices which employ the aid of weights to provide resistance against the user's direction of motion due to exertion of muscular force. Such machines occupy a large amount of space, relatively cumbersome and are quite expensive. They do not "possess the fidelity of adjustability" and are inherently heavy due to the intrinsic use of weight-stacks to provide resistance. This was an especially important aspect as heavier devices require much more launch force in order to escape the Earth's gravitational pull; this would require more rocket fuel, more money and would result in more pollution as a result.

Accordingly, a device was designed to simulate the resistance provided by weights (on Earth) in a zero or micro-gravity environment which is "compact with relatively low mass, provides for numerous different exercises, is adjustable for different loads, is adjustable for different sized individuals and will operate for long periods with minimal maintenance."

Crew-members are prescribed a personalized exercise plan, which they can easily access through the use of the integrated touchscreen in the exercise device. A crew-member can select an exercise from their prescription, or choose any of the other exercises available to perform. The exercises are then performed through the use of a lift bar or cable assembly depending on the motion of muscular exertion required by the exercise. Resistive load can be adjusted between 0 and 600+ pounds for bar-related exercises and 150 pounds for cable-related exercises.

Research

The first-ever muscle-focused analyses of astronauts from the International Space Station revealed that a six-month period in near zero-gravity yielded a fifteen percent loss in muscle volume and twenty five percent loss in strength. The results concerned scientists since astronauts were already following a strict, previously defined workout to prevent the loss of bone and muscle, however, it was now apparent that this workout did not prevent the loss of muscle mass, but rather lessened the rate of diminishing muscle in space station astronauts.

Considering this new information, more research was conducted to gather additional data required to design a completely new machine which would minimize or potentially erase the diminution of muscle mass on lengthy space station flights.

Bone loss was predominantly considered to be an issue which affected female space travellers over long periods of time. This was due to the largely male dominated astronautical personnel, however, the number of female space explorers has now risen such that a "quantitative comparison of changes in bone and renal stone risk by sex" is now validated. Bone demineralization during space flight has been proven to catalyse the production kidney stones.

Prototype Subsystems

The Advanced Resistive Exercise Device consists of several distinct subsystems, including more intricate systems even further down the hierarchy of subsystem, however, there are a few major components which significantly contribute to the proper functioning of the device. Below are the major subsystems incorporated into the aRED:

• The frame-and-platform assembly creates the spine which supports all other subsystems and components.
• The vacuum cylinders provide the resistance required for the exercises. They consist of consumer grade, off-the-shelf pneumatic cylinders. They can be recharged from a vacuum source.
• The arm base assembly houses the load-adjustment mechanism and contributes to the overall load path.
• The wishbone arm (lift bar) gives the user the ability to perform squat, dead lift and other bar exercises. The wishbone arm is the other half of the direct load path from the arm base (above) to the user.
• The cable-and-pulley system is incorporated to primarily allow the user to perform long-stroke, low-load movements. This mechanism is attached to the arm-base assembly.
• The flywheel mechanism houses the components which simulate the inertial constituent of free-weight exercises under a gravitational force equivalent to the one on the Earth's surface. It is not dependent on gravity to function, therefore, it functions as intended under a gravitational force such as the one on Earth, as well as in zero gravity environments such as the International Space Station.

The Advanced Resistive Exercise Device was designed to last 15 years, with a total life of over 11.2 million cycles. This ensures maximum efficiency due to the minimal time and money exhausted on the maintenance and replacement of the exercise machine over consecutive missions on the International Space Station.

Purposes

Reviewing the concerning results from the first-ever muscle analysis from the International Space Station, researchers realized that the relatively large percentage of muscle mass and strength lost during extensive flights could prove detrimental to crew members due to the high probability of the lost muscle mass being permanently dissipated. However, crew members were already following a “strict workout routine designed to prevent the loss of bone and muscle”. Therefore, a new device was designed to address the limitations of the previously utilized exercise machine, the Interim Exercise Device (iRED) and “serve as the next generation of in-flight resistance exercise hardware on the International Space Station.”

The Advanced Resistive Exercise Device was introduced on spaceflight missions after the 14th of November, 2008, and replaced the previously utilised iRED. It was implemented as a countermeasure to provide efficient protection against the loss of body mass, muscle strength, bone mass and aerobic capacity within the environmental constraints on the International Space Station.

Effects

Due to the nature of the research which highlighted the problem which the Advanced Resistive Exercise Device was designed to solve, there is no substantial research conducted into the long term effects of the aRED. However, sufficient research was conducted into the direct effects of the aRED to draw out conclusions on its long term results; an experiment was designed to compare the results of the aRED regarding muscle mass and strength with the results produced by similar free weight exercises in the same time frame.

Muscle Volume and Strength

An experiment was conducted to compare the effectiveness of the aRED and free weight training in promoting muscle growth and strength gains in selected subjects prior to the installation of the aRED on the ISS; In determining these aspects, it was important to comprehend subjects that were untrained as well as experienced subjects that have undergone pre-workout that was implemented specially for the aRED.

"Twenty untrained subjects were assigned to either the ARED (8 males, 3 females) or free weight (6 males, 3 females) training group and participated in a periodized training protocol" (16 weeks) consisting of squats, heel raises and deadlifts 3 times per week. An MRI was used to measure muscle volume both pre- and post-training. The resulting images were then analysed and summed.

It was determined from the experiment that the increase in muscle hypertrophy and strength following aRED training "is not different than" free weight training. This indicates that the Advanced Resistive Exercise Device is highly probable to protect crew members against lengthy-spaceflight-induced muscle mass atrophy and strength loss.

Bone Mineral Density Adaptations

Another experiment was conducted in a similar time-frame but focused on comparing the effects of training on the aRED to free weights in regard to bone mineral density (BMD) which is vital to make sure that the participants and users would generally have a beneficial output after working out on the aRED.

Nineteen male and female volunteers were assigned to either the aRED (11) or free weight (8) training groups and performed squats, heel raises and deadlifts 3 times per week for 16 weeks. "Dual energy X-ray absorptiometry was used to assess BMD of the lumbar spine and femoral neck before and after training."

Exercising on the aRED provides almost equivalent results compared to free weight exercises with regard to stimulating increased BMD in the lumbar spine and femoral neck. This indicates that the Advanced Resistive Exercise Device will likely prevent spaceflight-induced BMD loss in crew members.

Kidney Stones

A separate experiment was conducted, focusing specifically on the effects of the aRED on the previously highlighted risks of amassing renal stones over the course of lengthy space flights.

Data was taken from 42 astronauts ranging from ISS expeditions 1-32 and compiled, analysed and separated into two distinct data sets depending on the exercise equipment which was available on their space expeditions; voyages launched before 14th November, 2008 were performed with the Interim Resistive Exercise Device (iRED) while expeditions launched after 14th November, 2008 utilised the Advanced Resistive Exercise Device.

The results determined that there was an increase regarding the risk of formation of renal stones during and after spaceflight. However, dissimilar to previous experiments, this experiment was able to provide a statistical analysis referring to which sex held the largest risk of forming kidney stones during lengthy space flight expeditions. According to the conducted experiment, it was highlighted that the male astronauts experienced a greater risk before and after flight in reference to the formation of kidney stones. However, it should be noted that the results during the spaceflight were not significantly different between the two sexes.Therefore, there is insufficient evidence to conclude that there is a statistically significant difference between males and females in the risks associated with the formation of kidney stones during lengthy space flights.