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Ground Based Study:    iRATS14
Launch/Start Date:
Landing/End Date:
160 days

NASA scientists are working to find ways to keep astronauts healthier and safer after spending prolonged periods in space. Current flight exercise countermeasures are not fully protective of cardiovascular, muscle, and bone health, thus there is a need to refine and optimize the countermeasures. This feasibility study aims to determine whether two weeks of pre-bed rest training is enough to prepare subjects to perform the in-bed rest exercise program. The study will also measure the caloric cost to perform the exercises while using a horizontal bed position.

This study was conducted at the Flight Analogs Research Unit (FARU) at the University of Texas Medical Branch (UTMB) in Galveston, Texas during 14 days of bed rest with a maximum of ten subjects participating. The primary purpose was to study and evaluate the effectiveness of a new exercise program to maintain muscle size and strength, bone health, and cardiovascular function. The Integrated Resistance and Aerobic Training (iRAT) program included high intensity interval-type aerobic exercises on alternating days with continuous aerobic exercise. Resistance exercise was performed 3 days per week on the same day as the continuous aerobic exercise, but separated by 4-8 hours. Secondly, this study assessed and quantified the accuracy of leg muscle size measurements performed by ultrasound compared to magnetic resonance imaging (MRI).

The study consisted of pre testing of 14 days, called the ambulatory period, in which the subject underwent a series of tests to determine the normal muscle, heart, and circulatory systems state. Following the ambulatory period, the subject remained in a horizontal bed position for 14 days, confined to strict bed rest, except for limited times for specific tests. The final 7 days or the recovery period of the study was mainly for the subjects reconditioning period in which the subject slowly resumes normal physical activity.

Some of the tests that were conducted during this feasibility study included:

  • Screening tests: Isokinetic Fitness and the Cycle Ergometry Test were assessed as a subject screening measurement and were performed more than 30 days prior to the start of the study; likewise a simple blood test and ECG (heart rate and rhythm test) were measured.

  • Diet and Input/output Monitoring (CRF): The subject was fed a carefully controlled diet, and all urine will be collected for scientific analyses.

  • Biological Sample Collection: blood samples were collected and Vitamin D Supplementation was administered.

  • Clinical Laboratory Assessment (MR010G): This examination included a collection of blood and urine from subjects for analyses to enhance the physician’s medical evaluation of the subject’s health, medical fitness, and post-bed rest recovery.

  • Physical Fitness Assessment: Cycle Ergometry (MR080G): Exercise tests were conducted before bed rest and after bed rest. These tests are performed on a cycle ergometer with the subject in the upright (seated) position.

  • Physical Fitness Assessment: Isokinetic Testing (MR079G): Muscle performance before and after bed rest was assessed. The concentric strength of the knee, ankle, and trunk extensors and flexors was tested using an isokinetic dynamometer.

  • Leg Press Muscle Function (MR078G): was performed on a leg press machine as the subject’s feet are resting on a footplate.

  • Surveillance of Ocular Parameters and Visual Function in Bed Rest Subjects (Ocular_Test).
    (PI: Ronita Cromwell, Ph.D. USRA, NASA Johnson Space Center, Houston, Texas and PI: Gianmarco Vizzeri, M.D., University of Texas Medical Branch, Galveston, Texas)
    A battery of nine tests will be used to assess ocular health. The tests are designed to gather data on visual acuity, retinal health and structures, strabismus, ocular muscle function, peripheral vision, papillary reflex, intra-ocular pressure and eye refractive error.

  • MRI Scan: A magnetic resonance imaging (MRI) was used to look at the size of the leg muscles.

  • Ultrasound Scan: ultrasound (sound waves) to examine the size of the muscles.

  • Metabolic Cost of Exercise Sessions: The metabolic cost of each of the exercise protocols performed during bed rest was evaluated using a commercial metabolic gas analysis system.

  • Resting Metabolic Rate (RMR): RMR may increase throughout bed rest due to performance of exercise or may decrease due to reduced activity.

  • Integrated Resistance and Aerobic Training Study – Bedrest. (PI: Ploutz-Snyder, Lori, PhD, University Space Research Association (USRA), Houston, Texas)
    Exercise training was conducted during bed rest in the lying down position on specially designed exercise equipment called the stand-alone Zero Gravity Simulator (sZLS) vertical treadmill and resistance exercised using the Horizontal Exercise Fixture (HEF). The Resistance Exercise consisted of a series of squats, lifts, leg/knee extensions, heel raises, bench presses, shoulder presses, and elbow extensions.