A ground-based comparison of the Muscle Atrophy Research and Exercise System (MARES) and a commercially available isokinetic dynamometer

Kirk L. English, Kyle J. Hackney, John K. De Witt, Robert J. Ploutz-Snyder, Elizabeth L. Goetchius, Lori L. Ploutz-Snyder

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Introduction: International Space Station (ISS) crewmembers perform muscle strength and endurance testing pre- and postflight to assess the physiologic adaptations associated with long-duration exposure to microgravity. However, a reliable and standardized method to document strength changes in-flight has not been established. To address this issue, a proprietary dynamometer, the Muscle Atrophy Research and Exercise System (MARES) has been developed and flown aboard the ISS. The aims of this ground-based investigation were to: (1) evaluate the test-retest reliability of MARES and (2) determine its agreement with a commercially available isokinetic dynamometer previously used for pre- and postflight medical testing. Methods: Six males (179.5 ± 4.7 cm; 82.0 ± 8.7 kg; 31.3 ± 4.0 yr) and four females (163.2 ± 7.3 cm; 63.2 ± 1.9 kg; 32.3 ± 6.8 yr) completed two testing sessions on a HUMAC NORM isokinetic dynamometer (NORM) and two sessions on MARES using a randomized, counterbalanced, cross-over design. Peak torque values at 60° and 180° s-1 were calculated from five maximal repetitions of knee extension (KE) and knee flexion (KF) for each session. Total work at 180° s-1 was determined from the area under the torque versus displacement curve during 20 maximal repetitions of KE and KF. Results: Intraclass correlation coefficients were relatively high for both devices (0.90-0.99). Only one dependent measure, KE peak torque at 60° s -1 exhibited good concordance between devices (p = 0.92) and a small average difference (0.9 ± 17.3 N m). Conclusion: MARES demonstrated acceptable test-retest reliability and thus should serve as a good tool to monitor in-flight strength changes. However, due to poor agreement with NORM, it is not advisable to compare absolute values obtained on these devices.

Original languageEnglish (US)
Pages (from-to)3-9
Number of pages7
JournalActa Astronautica
Issue number1
StatePublished - 2013
Externally publishedYes


  • ISS
  • Microgravity
  • Peak torque In-flight
  • Spaceflight
  • Strength test

ASJC Scopus subject areas

  • Aerospace Engineering

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