Subjects performed two testing sessions each using NORM and MARES (four total testing sessions) using a balanced, randomized, cross-over design. During each session, peak torque values were measured during two testing sets: 1) five maximal, discrete repetitions of isokinetic knee extension and knee flexion at 60 degrees, and 2) 21 maximal, continuous repetitions of knee extension and knee flexion at 180 degrees. The first repetition of the second testing set was discarded; repetitions two through 21 were analyzed. Total work was also determined for these 20 repetitions from the area under the torque versus displacement curve. All testing was performed over a 75 degree range of motion (95 degree flexion to 20 degree extension) that was determined from a 90 degree anatomical reference measured by a goniometer. Warm up consisted of four submaximal repetitions and two maximal repetitions at the prescribed testing velocity before performance of that velocity-specific testing set. Subjects rested two minutes between each warm up and test set.
All testing was conducted using the right leg with the exception of one subject who had a pre-existing right leg injury. For this subject, the left leg was used. Subjects were positioned uniformly on each device and the position settings recorded to enable a reproducible set up. Subjects completed both sessions within one device before proceeding to testing with the other. Each testing session was separated by at least two days. Subjects refrained from any exercise in the eight hours before testing and from strenuous exercise 24 hours prior to testing. NORM testing was conducted by two Exercise Physiology and Countermeasures Project (ExPC) personnel; MARES testing was similar but included the addition of a MARES engineer. MARES testing used the Science and Operations Evaluation Plan (SOEP). Data were obtained using the manufacturer-provided HUMAC software.
The results of this single, relatively small-n investigation demonstrates 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 is particularly relevant to future flight studies that will use MARES as an in flight testing device; to compare pre- and post-flight strength measurements to those obtained in flight, pre- and post-flight strength testing should be conducted using MARES.
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