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Nutrition Coupled with Traditional Resistance or Low-Load Blood Flow Restricted Exercise during Human Limb Suspension (EORS_TIMED)
Principal Investigator
Research Area:
Exercise physiology
Metabolism and nutrition
Muscle physiology
Species Studied
Scientific Name: Homo sapiens Species: Human

During periods of muscular inactivity such as with exposure to microgravity, bed rest, or unilateral lower limb suspension (ULLS), decrements in skeletal muscle size, strength, and endurance have been observed. During long-term space flight the aforementioned reductions in skeletal muscle function could negatively influence overall crew health and increase the risk of impaired performance on mission related tasks. Previous research has demonstrated that the most effective countermeasure to disuse induced muscle atrophy is traditional resistance exercise, which has been shown to maintain muscle size and strength during prolonged periods of bed rest. However, implementing traditional load resistance exercise during long-duration space flight is not without difficulty due to: a weightless environment, limited space for equipment, risk of crew injury, complexity and/or unreliability of exercise equipment to deliver high loads and a substantial risk to space craft’s structure. Therefore, if similar skeletal muscle benefits could be obtained with low load resistance training, this could be an attractive option, at least for circumstances in which high load exercise equipment is unavailable (confined space, severely limited upmass, equipment failure, etc).

Exercise is not the only factor that determines the adaptations observed in skeletal muscle during a period of disuse. Nutrient intake provides a potent metabolic stimulus independent of exercise and these factors can work synergistically. In this capacity, there is growing evidence to support nutrient timing (ingesting protein or amino acids and carbohydrate within approximately 30 minutes before or after a resistance training session) as an effective strategy to promote muscle growth. Previous studies in ambulatory subjects have shown that consuming a combination of amino acids and carbohydrates immediately before or after an exercise session stimulates muscle protein synthesis to a greater extent than when performing the same exercise when fasted. In studies focusing on disuse, timing essential amino acids with carbohydrate before (less than five minutes) or after (three hours) resistance training has recently shown to attenuate the loss of muscle mass and strength during 28 days of bed rest even when the body is in an overall energy deficit . Thus, there appears to be strong support for consuming a protein-carbohydrate source that is rich in essential amino acids before or after each resistance training session in order to optimize training adaptations and this strategy is effective even during energy restriction. Combining milk intake with resistance exercise training has also shown to increase muscle fiber size compared to fat-free soy milk and an isoenergetic carbohydrate supplement.

Specific Aims:

1. To determine the morphological and neurological alterations that occur in skeletal muscle following combined exercise and nutritional countermeasures during disuse (unloaded-left limb) and use (loaded-right limb).
2. To characterize local (calf and thigh) blood flow, tissue oxygen saturation, tissue pH, limb circumference, heart rate, systemic blood pressure, and stroke volume during low load, low load with low blood flow restriction (BFR), low load with moderate BFR, and high load resistance training.
3. To compare the effects of 30 days of traditional high load and low load with moderate BFR resistance training in the weight-bearing and non-weight-bearing limb on popliteal and femoral blood flow and diameter, and tissue oxygen saturation and pH at the calf and thigh.

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Hackney KJ, Everett M, Scott JM, and Ploutz-Snyder L. Blood flow-restricted exercise in space. Extreme Physiology and Medicine. 2012. Dec 1; 1(1):12. . []

Musculoskeletal physiology

Data Information
Data Availability
Archive is complete. Data sets are not publicly available but can be requested.
Data Sets+ Request data

Anabolic resistance
Artery diameter
Blood flow over time
Blood flow velocity
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Mission/Study Information
Mission Launch/Start Date Landing/End Date Duration
ECP 02/01/2005 12/31/2010 In Progress

Additional Information
Managing NASA Center
Johnson Space Center (JSC)
Responsible NASA Representative
Johnson Space Center LSDA Office
Project Manager: Jessica Keune
Institutional Support
National Aeronautics and Space Administration (NASA)