COMBINED EFFECTS OF NUTRITIONAL AND EXERCISE COUNTERMEASURES

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Background: This experiment will simulate many of the physical conditions experienced by astronauts during spaceflight by examining the effects of resistance exercise (weight training), nutrition and a stress hormone (cortisol) on muscle during 28 days of bedrest. Specific Aims and Procedures (summary): To determine if a combination of resistance exercise and amino acid supplementation can reduce muscle loss and maintain muscle function during 28 days of bedrest by mimicking the diet of astronauts during spaceflight by providing approximately 80% of the calories normally ingested during daily life. Experimental Design (summary): This study will include normal healthy subjects between the ages of 18-50. Subjects will undergo a comprehensive screening visit prior to participating and will be assessed by multiple members of the research team. The study involves a 36-day in-patient stay in the GCRC with two nine hour metabolic studies. The metabolic studies will take place on days 6 and 34 of bedrest. Cortisol will be administered throughout the 28 day bedrest portion of the study to increase blood cortisol levels to those experienced in spaceflight. Subjects will be randomly assigned to one of six experimental conditions (please refer to page 2 of the consent form). Subjects will be required to return to the GCRC for three additional 30 minute follow-up visits two weeks following the study. Significance (summary): Information derived from these studies will allow a better understanding of the mechanisms involved in the response of muscle protein metabolism to exercise, inactivity, and nutrition.