Interim Resistive Exercise Device (iRED) - 01.16.19

Summary | Overview | Operations | Results | Publications | Imagery

ISS Science for Everyone

Science Objectives for Everyone
Long duration exposure to micro-gravity causes muscle atrophy, loss of strength and deterioration of bone mass.  A key element in the crew countermeasures will be to provide resistive exercise to prevent this kind of deterioration.  The Interim Resistive Exercise Device (IRED) is designed to prevent atrophy of the major muscle groups and to minimize bone loss in the zero gravity environment by maintaining strength, power, and endurance.
Science Results for Everyone
Information Pending

The following content was provided by Ray M. Eid, and is maintained in a database by the ISS Program Science Office.
Facility Details


Facility Manager(s)
Ray M. Eid, Johnson Space Center, Houston, TX, United States
Ryan Mitchell Lien, Johnson Space Center, Houston, TX, United States

Facility Representative(s)
Information Pending

NASA Johnson Space Center, Houston, TX, United States

Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)

Sponsoring Organization
Human Exploration and Operations Mission Directorate (HEOMD)

ISS Expedition Duration
March 2001 - December 2002; November 2002 - May 2003; April 2003 - September 2011

Expeditions Assigned

Previous Missions
Information Pending


  • Retired/Returned/Disposed
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    Facility Description

    Facility Overview

    • The interim Resistive Exercise Device (iRED) is used onboard ISS to aid in the maintenance of muscular strength. Crewmembers exercise daily on iRED to maintain their preflight muscle and bone strength and endurance.  iRED is retired as of October 2011, and its replacement is the Advanced Resistive Exercise Device, or ARED, which was taken to the International Space Station on space shuttle mission STS-126 in November 2008.


    • On ISS, the iRED can be configured to allow performance of at least 18 different exercises for both upper and lower body muscles.


    • The iRED provides a load of up to 300 pounds of resistive force for countermeasure exercise. Resistive exercise helps astronauts maintain strength and endurance.


    • The iRED accommodates all crewmembers, from the 5th percentile Japanese female to the 95th percentile American male.

    iRED consists of five distinct assemblies: 

    Flexpack Assembly - The iRED Canister contains 12 pairs and 2 single flex packs and numerous other parts.  Mechanical-Lifecycle testing of the can resulted in 149,000 cycles before failure of a flex pack occurred.

    Canister Cord Assembly - Life cycle testing of the various iRED canister-cord options was performed to determine the cord that would provide the longest life, and thus reduce the number of replacements required on-orbit.  The cord test rig utilized completely flight-like cord interface hardware (Spiral Pulley and Outlet Rollers) to arrive at the ideal cord candidate/design and certifiable cycle-life.

    Harness Cord Assembly - the Squat Harness includes cords constructed of the same material as the iRED Can cords.  The harness is used for only some exercises and at a wide range of loads and motions.

    Squat Harness Assembly - the iRED Squat harness contains a latch and latch-bolt held in place by a non-captive fastener.  The iRED Squat Harness contains a pair (right and left) of interchangeable pads for each Increment crew member.  It is possible for these items to become worn or soiled; therefore, spares are flown in the iRED Resupply kit with each crew rotation.

    Calibration Tool Kit Assembly - the iRED Calibration Tool Kit assembly contains a mechanical gauge calibration tool.  The calibration tool was originally serviced and calibrated by the vendor.   A ground unit mirrors on-orbit use by performing “mock” calibration with ground iRED canisters as required (approximately every two months).  Ground based testing is still in progress on the “fleet-leader” unit estimated to last 48 months.  

    The iRED will operate in the following modes:

    • Squat Harness is used to perform squats, straight-leg Deadlift, bent-leg Deadlift, and heal raises.
    • Short Bar Assembly is used to perform straight leg deadlifts, bent-leg deadlifts, bend-over rows, upright rows, bicep curls, shoulder presses, sit-ups, bench presses and wrist curls.
    • Hand cranks are used to adjust the resistance.
    • Hand grips used to perform hammer throws, shoulder raises, shoulder presses, bicep curls, tricep extensions, wrist curls, bent-over rows, and upright rows.
    • Ankle cuffs used to perform hip abductions / adductions, knee raises, and leg curls.
    • Resistance - Each IRED canister shall provide a maximum resistive load of at least 150 pounds at the highest load setting.  With two canisters the maximum resistive load will be 300 pounds. At the lowest load setting, each IRED canister shall provide a resistive load not to exceed 30 pounds.
    • Adjustability - For resistances of 100 pounds or less, adjustability shall be in increments of five pounds resistance at an accuracy of 1 pound or +5% of current reading, whichever is greater. For greater than 100 pounds, adjustability shall be in increments of 10 pounds resistance at an accuracy of 1 pound or +5% of current reading, whichever is greater.
    • iRED has been stowed and occasionally used in its current mode of operation as a contingency to ARED

    Inspections every 2 weeks will be performed to verify hardware has not sustained damage during use.  Four spare harness cords will be flown in the iRED Maintenance Kit and resupplied as necessary.

    Inspections to verify that all the fasteners remain secure, inspections are required once per month.  If tightening is required, it should be performed during these inspections.

    Periodic maintenance of the iRED restraint cords, attachment bolts and harness cords and complete replacement of the iRED Cans will be required to ensure safe operation of the device.  The periodic maintenance, inspection, and replacement of the indicated items provide the necessary controls to comply with associated hazards of a hardware failure. Based on accepted engineering practices for the iRED system, the iRED engineering team established a conservative schedule of  inspections every two weeks to verify the hardware has not sustained damage during its nominal use.

    Video documentation depicting on-orbit use of the IRED Hardware system is required for each crew member.  This data is used to evaluate their interaction with the hardware identifying any engineering, safety, or exercise form issues.  Video data ensures that all hardware constraints levied by the engineering team are being maintained; ensure that proper safety measures are being employed to control for any and all identified hazards; ensure that the proper exercise form and methods are utilized to prevent crew injury stemming from improper form. Video will be recorded within the first 30 days of the start of each increment to identify any of the above issues.  Necessary changes or issues will be addressed and the crew members will be informed of any necessary corrective actions.  A second video session will be performed between 60 and 90 days  of the increment to ensure the issues have been remedied and no new concerns have surfaced.

    With humans currently occupying the International Space Station (ISS) for six months and space exploration missions of one to three years on the horizon, preservation of crewmember health and fitness is a major objective of the international space community. Exercise has been the primary utility used by the space agencies in an effort to protect cardio-vascular, bone, and skeletal muscle health while in space for extended stays.

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    Facility Operations

    • The iRED contains a series of 16 flex packs stacked vertically inside cylindrical canisters and is designed to provide resistance training for crewmembers in microgravity. A flex pack consists of a ring disk aluminum outer rim, with rubber spokes protruding inward toward a center hub.


    • The flex packs revolve about a metal axle. When the metal axle is turned, the rubber spokes are stretched, increasing the resistance offered by the device.

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    Decadal Survey Recommendations

    Information Pending

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    Results/More Information

    In order to assess the effectiveness of the proposed countermeasure, ground reaction forces, muscle forces, and joint reaction forces must be compared to iRED and normal 1-G activity. If countermeasure exercise is capable of exceeding the loading environment created when the iRED is used in microgravity, then muscle and bone strength might be maintained to a greater extent than currently observed with astronauts on the ISS.  The maximum ground reaction force (GRF) per leg, which was produced from two-legged squats on iRED in parabolic flight, was 76 lbs, or nearly 0.5 body weight (BW). GRFs produced per leg during a one-legged squat were 144% higher than from a two-legged squat using iRED.  Similarly, GRFs from two-legged squats were 33% higher than from two-legged squat on iRED.  The largest GRF experienced by the subject in this study was 1.2 BW.  Peak GRF experienced when walking in 1-G is 1.5 BW. When accounting for the maximum 0.5 BW that is added to simulate a vibrating platform (peak GRF = 1.7 BW), the GRF of this study exceeds that of 1-G walking. In a recent study, average single leg forces for two-legged squat using iRED on the ISS was found to be 0.59 BW, and that for one-legged squat was found to be 0.64 BW. Simulated vibration exercise was confirmed to be a highly effective stimulant for both muscle and bone, as demonstrated by the considerable increase in muscle forces and joint reaction forces.  Vibration could offer the necessary stimulus to further attenuate muscle degradation as well as preserve bone density.

    Current countermeasures on the International Space Station (ISS), such as resistive exercise on the interim Resistive Exercise Device (iRED) or Advanced Resistive Exercise Device (ARED), treadmill running, and cycling, have only proven to be partially beneficial despite over four decades of optimization.  In particular, astronauts returning from six months aboard the ISS have shown that anti-gravity muscle volume and peak power still decrease significantly versus pre-flight (-13% and -32%, respectively). Bone mineral density (BMD) and strength losses also persist in the lower extremities with integral hip BMD being lost at an average of 1.5% per month.  Such losses must be blunted to ensure safety of astronauts for extended duration excursions beyond low-Earth orbit (Goel et al. 2012).

    Results Publications

      Goel , Kaderka , Newman DJ.  Modeling the benefits of an artificial gravity countermeasure coupled with exercise and vibration. Acta Astronautica. 2012; 70: 43-51. DOI: 10.1016/j.actaastro.2011.07.021.

      English KL, Lee SM, Loehr JA, Ploutz-Snyder RJ, Ploutz-Snyder LL.  Isokinetic strength changes following long-duration spaceflight on the ISS. Aerospace Medicine and Human Performance. 2015 December 1; 86(12): 68-77. DOI: 10.3357/AMHP.EC09.2015.

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    Ground Based Results Publications

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    ISS Patents

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    Related Publications

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    Related Websites

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    NASA Image: ISS010E05354 - Astronaut Leroy Chiao, Expedition 10 commander and NASA ISS science officer, uses the short bar for the Interim Resistive Exercise Device (IRED) to perform upper body strengthening pull-ups. The iRED hardware is located in the Unity node of the International Space Station (ISS). 

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    NASA Image: ISS017E006639 - NASA astronaut Garrett Reisman, Expedition 17 flight engineer, wearing squat harness pads, performs knee-bends using the Interim Resistive Exercise Device (IRED) equipment in the Unity node of the International Space Station.

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    NASA Image: S112E05165 -  Mission specialist Sandra Magnus and Expedition 5 Science Officer Peggy Whitson are photographed in the International Space Station (ISS) Node 1/Unity module working with the Interim Resistive Exercise Device (IRED) and Handcrank Assembly - Fore.

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