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RESEARCH INTERESTS
- 1. SPACE BIOLOGY. The National Aeronautics and Space Adminsitration (NASA) has plans to conduct manned missions to Mars in the beginning of the 21st century. One of the major problems currently preventing such an expedition is the loss of bone and muscle mass in the micro-gravity environment. A primary interest of the Fitts' laboratory is to understand the effects of prolonged space flight on skeletal muscle stucture and function, and develop effective exercise countermeasures that prevent or greatly reduce muscle atrophy. We have completed two short duration space flights. The first which flew in June of 1996 was a human mission aboard the space shuttle
Columbia called Life and Microgravity Space Lab (STS-78). In this flight, we studied the affects of 17 days of micro-gravity on the crew's physical work capacity, calf muscle function, and the biochemical and physiological properties of individual slow and fast twitch fibers isolated via needle biopsies of the soleus and gastrocnemius muscles. Results from this mission were published in a series of papers (J Physiol 516(3): 915-930, 1999; J Appl Physiol 88: 567-572, 2000; J Appl Physiol 90: 2203-2211, 2001; J Appl Physiol 91: 57-64, 2001). The second flight flew in December 1997on the Russian BION space capsule, and studied the effects of micro-gravity on single fiber function in rhesus monkeys. The results from this project were published in three papers (J Appl Physiol 84: 1776-1787, 1998; J Appl Physiol 86: 335-340, 1999; Am. J. Physiol. 279: R1546-R1557, 2000). From these flights, we identified the major muscle proteins and substrates that are affected by space flight, and made considerable progress towards understanding the causes of space flight induced muscle weakness and reduced work capacity. Currently, we are studying the crews aboard the International Space Station to determine the effects of prolonged microgravity on skeletal muscle structure and function. Following these studies, we will be able to model the muscle changes that would occur in a very long duration mission, such as, a trip to Mars. Additionally, we are working with land models of micro-gravity ( bed rest in humans) to elucidate the cellular and molecular causes of the selected protein loss, and develop effective countermeasures (exercise and diet) to prevent the muscle wasting. A summary of the effects of microgravity and skeletal muscle can be found in a recent reviews by Dr. Fitts and colleagues (J Appl Physiol 89:823-839,2000; and J Exp Biol 204: 3201-3208, 2001).
- 2. MUSCLE FATIGUE. The Fitts' lab has a long standing interest in elucidating the cellular causes of limb muscle fatigue. Dr. Fitts has published a number of review articles on the topic (Physiol. Rev.74:49-94, 1994; Handbook of Physiology, Section 12, Exercise: Regulation and Integration of Multiple Systems, Chapter 26, pages 1151-1183, 1996; and Principles of Exercise Biochemistry 3rd Edit. In: Med Sports Sci 46:279-300, 2004). Currently, the lab is working to understand the role of a reduced intracellular pH and an elevated inorganic phosphate in the fatigue process. These studies are evaluating the effects of these ions on both excitation-contraction coupling and the cross-bridge cycle.
