Muscle Atrophy Research and Exercise System (MARES) - 10.21.14
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The Muscle Atrophy Research and Exercise System (MARES) will be used for research on musculoskeletal, biomechanical, and neuromuscular human physiology to better understand the effects of microgravity on the muscular system.
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European Space Research and Technology Centre (ESTEC), Noordwijk, , Netherlands
Sponsoring Space Agency
European Space Agency (ESA)
ISS Expedition Duration
September 2010 - Ongoing
Previous ISS Missions
- MARES enables scientists to study the detailed effects of microgravity on the human muscle-skeletal system. It also provides a means to evaluate countermeasures designed to mitigate the negative effect, especially muscle atrophy.
- The MARES hardware is made up of an adjustable chair and human restraint system, a pantograph (an articulated arm supporting the chair, used to properly position the user), a direct drive motor, associated electronics and experiment programming software, a linear adapter that translates motor rotation into linear movements, and a vibration isolation frame.
- MARES is capable of supporting measurements and exercise on seven different human joints, encompassing nine different angular movements, as well as two additional linear movements (arms and legs). It is considerably more advanced than current ground-based medical dynamometers (devices used to measure force or torque) and a vast improvement over existing ISS muscle research facilities.
- MARES is integrated into a single International Standard Payload Rack (ISPR), called the Human Research Facility (HRF) MARES Rack, where it can also be stowed when not in use. It may be used together with an associated device called the Percutaneous Electrical Muscle Stimulator (PEMS II).
The main box contains the powerful MARES direct drive motor which provides the core mechanical stimulus of the facility. The motor is capable of producing torques in the range of 3 Nm to 900 Nm. To give some examples of common torque values from "everyday life", a Black and Decker Cordless drill has about 12 Nm of torque, a 20 cm wrench with 120 N of force applied (about 30 lbs) gives 24 Nm of torque and a 2002 Ford Focus ZTS running at 4500 RPM has 183 Nm of torque.
This MARES direct drive motor is capable of producing rotation at angular velocities between 5 degrees/sec and 515 degrees/s, or 343 degrees/s for eccentric motion. The main box also contains power, control, supervision, and servo drive electronics, cooling fans, and a connector panel used to connect the HRF workstation and other external devices to MARES, such as PEMS II.
The MARES motor may need up to 8 kW to accelerate but only for some tens of milliseconds. To minimize peak external power usage, MARES employs a battery, housed in the main box, which distributes these short power spikes over longer time periods. Using the battery as a buffer, MARES will consume an average of 150-200 W during a typical experimental session.
The human restraint system includes the fully adjustable chair that the crewmember sits on, as well as a set of adjustable levers, connectors, pads, restraints, and handgrips designed by biomechanics experts to support the nine joint configurations with subjects ranging from 5 to 95 percentile in size. The restraint system aims to isolate muscle groups under study and maintain the alignment of the joint and motor axes, while maintaining an acceptable subject comfort. The restraint system also includes a pantograph, which is capable of translating and rotating the chair into a wide range of positions relative to the main box.
The linear adapter is used to convert the motor rotation into linear movements. It can be used for exercising one or both arms or legs at any inclination and includes force and torque sensors at the handgrips.
The vibration isolation frame is used to keep facility forces internal to MARES by mechanically isolating MARES from the ISPR seat track and the ISS.
Finally, the laptop allows for the crewmember to control and monitor MARES operations, including set-up procedures, experiment steps, data display, data processing, results summaries, and programming of a desired experiment/exercise scenario.
The MARES software is designed to clearly guide the subject/operator through all steps with tailored instructions, including text, graphics, and interaction prompts. It is fully programmable, allowing the user to set up complex movements by selecting from a pre-defined set of basic control algorithms for the motor, known as basic motion units (BMUs), and building up a sequence of exercise steps or routines.
There is a BMU for each mode of muscle contraction, including: isometric (muscle contraction at a fixed length, i.e. no movement), isotonic concentric (muscle shortens as it contracts at a constant torque), isokinetic concentric (muscle shortens as it contracts but at a constant velocity), isotonic and isokinetic eccentric (muscle extended). In addition, there are eleven more BMUs used to support more sophisticated experimental setups, including: spring, friction, additional moment of inertia or mass, pseudo-gravitational, position control, velocity control, torque/force control, power control, physical elements, extended torque or force control and quick release.
BMUs can be combined into distinct MARES profiles to create complex motions and to simulate common exercise routines used on Earth. These profiles can be developed on the ground by collaborating scientists and medical operations officers and uplinked to the MARES.
In summary, MARES provides a flexible and accurate tool for studying the muscle-skeletal system in the microgravity environment. It will serve both the space research/human physiology communities, as well as the Medical Operations (MEDOPS) officers, who are responsible for maintaining crew health during long-duration space flight. MARES is capable of providing quantifiable stimuli to a wide range of space flight participants and accurately measuring these crewmembers' muscle performance. MARES will be launched inside a Multi-Purpose Logistics Module (MPLM). Once the MPLM is berthed to the ISS, MARES will be transferred to the Columbus Laboratory, where it will be deployed for operations.
MARES will be aisle-mounted to the seat tracks in the Columbus Laboratory and can be retracted and stowed by the crew in the HRF MARES rack when not in use.
When in use, the crewmember taking part an investigation will occupy the MARES seat and operate the facility using the MARES laptop. Crewmembers will also be responsible for setting up any desired external devices, such as the PEMS II or an electromyogram device (EMG; device used to measure electrical impulses of muscles).
Operations of MARES follow a set of computer-based instructions known as the MARES Experiment Procedures. These Experiment Procedures are made up of a sequence of prompts, MARES Profiles (which are in turn made up of a combination of BMUs; see above), commanding of external devices, displays of data, real-time processing of data, and steps to select data for storage and/or downlink. Experiment Procedures can be stored on the MARES prior to launch, or uploaded from the ground as new experiments or exercise routines are developed.
Finally, flight operations of MARES will be monitored and managed on the ground by a Tele-Science Center at NASA's Johnson Space Center and the Payload Operations and Integration Center at NASA's Marshall Space Flight Center.
- MARES will be aisle-mounted to the seat tracks in the Columbus Laboratory and can be retracted and stowed by the crew in the HRF MARES rack when not in use.
- When in use, the crewmember taking part in the investigation will occupy the MARES seat and operate the facility using the MARES laptop.
- Crewmembers will also be responsible for setting up any desired external devices, such as the PEMS II or an electromyogram device (EMG; device used to measure electrical impulses of muscles).
A Muscle Atrophy Research and Exercise System (MARES) unit was delivered to the International Space Station (ISS) in early 2010 which enables scientists to study strength changes in crewmembers during and not just after space flights. It is unknown whether space flight-induced strength losses occur in a linear fashion or whether they mirror those of aerobic capacity that occur mostly in the first few weeks of space flight. A strength change timeline featuring greater losses during the first days of flight would likely have significant operational implications. In flight strength testing capabilities will enhance countermeasures evaluation and facilitate improved prescription of crewmembers' in flight exercise programs over the duration of their flight.
In advance of its deployment on the ISS, a ground-based study was performed to evaluate the test-retest reliability of MARES, and determine its agreement with a standard, commercially available isokinetic dynamometer (the "HUMAC NORM" Testing and Rehabilitation System) often used for pre- and postflight medical assessment testing. Ten subjects participated in this project and completed 2 testing sessions each using NORM and MARES (4 total testing sessions). During each session, peak torque values were measured during 2 isokinetic testing sets: 5 maximal, discrete repetitions of knee extension and knee flexion at 60°/sec and 21 maximal, continuous repetitions of knee extension and knee flexion at 180°/sec.
Both devices show good similarity and acceptable test-retest reliability. However, within device standard deviations were 1.3 to 4.3 times larger for MARES than NORM indicating somewhat lower reliability for MARES. Only one dependent measure, knee extension peak torque at 60°/sec, exhibited good agreement between the two machines. Overall, agreement between NORM and MARES was poor. The results of this relatively small "n" (n = number of subjects) investigation demonstrate that MARES is a reasonably reliable device that renders consistent measurements between two sessions. However, MARES does not produce values that are in consistent agreement with NORM. Thus, until further research suggests otherwise, it is not advisable to compare values obtained on one device to those obtained on the other. This may necessitate testing crewmembers on both MARES and the commercially available dynamometer already in use for pre- and postflight medical assessment testing (English 2010).
Ground Based Results Publications
English KL, Hackney KJ, De Witt JK, De Witt JK, Ploutz-Snyder RJ, Goetchius EL, Ploutz-Snyder LL. A ground-based comparison of the Muscle Atrophy Research and Exercise System (MARES) and a commercially available isokinetic dynamometer. Acta Astronautica. 2012 Jul; epub. DOI: 10.1016/j.actaastro.2012.06.015.
Barattini P, Schneider SM, Edgerton R, Castellsaguer J. MARES: A New Tool for Muscular, Neuromuscular and Exercise Research in the International Space Station. Journal of Gravitational Physiology. 2005; 12: 61-68.
Test subject seated in the MARES human restraint system and using the linear adapter to exercise his arms.
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Collage of MARES hardware being tested on the ground with the test subject in various configurations.
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NASA Image: ISS024E014956 - NASA astronaut Shannon Walker, Expedition 24 flight engineer, works with Muscle Atrophy Resistive Exercise System (MARES) hardware during installation of MARES payload in the Columbus laboratory of the International Space Station.
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NASA Image: ISS025E005122: View of the final configuration of the Muscle Atrophy Resistive Exercise System (MARES) in the Columbus module as seen by the Expedition 25 crew.
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