Each year 40,000 - 70,000 individuals in the US are hospitalized for burn-related injuries, with 16% (6,400 to 11,200) having severe burns covering at least 20% of their total body surface area (BSA). Twenty years ago burns covering 50% BSA were fatal, while presently patients with 90% BSA burned are surviving. The outcome of these improvements in medical care is that hundreds of thousands of individuals endure the long- term consequences of burn injuries. For example, years following the burn injury fatigue is an almost universal complaint as a major barrier preventing such individuals from returning to work and performing activities of daily living 60, 65. We identified that ~76% of well-healed burned subjects (many years post-injury) have an aerobic fitness/capacity, measured by maximal oxygen uptake (V O2max), in the lowest 20th percentile relative to age and sex matched normative values 47. Based upon numerous studies relating aerobic capacity with mortality, cardiovascular risk, and quality of life, ~76% of severely burned individuals will have 3 to 5 fold greater mortality risk, have poorer general health, and will be more likely to require dependent care as they age 2, 15, 16, 86, 100, 116. Given these findings, the proposed work will address the following questions, the answers to which are vital to the health and full rehabilitation of the recovered burned patient: 1) What are the mechanisms resulting in low aerobic fitness in severely burned individuals years after the injury? 2) Can individuals who previously suffered significant burn injuries improve their aerobic capacity and if so by what mechanisms? To address these questions and related hypotheses, subjects who experienced severe burn injuries covering 20- 35%, 40-55%, and >60% of their BSA a minimum of 2 years prior to assessment will participate in a 6 month exercise training protocol. Prior to and followin the training protocol, subjects will be evaluated for aerobic capacity (V O2max), central and peripheral cardiovascular variables that influence VO2max (i.e., steady-state and maximum cardiac output, stroke volume, heart rate, and arteriovenous oxygen differences), and muscle biochemical and histological markers of improved oxidative capacity. Subjects will also be evaluated for left ventricular systolic/diastolic function, quality of life, body composition, and quantification of activities of daily living. These procedures will address the overall hypothesis that increases in VO2max (and related mechanisms) with exercise training in well-healed burned individuals are influenced by the extent of the burn injury. The obtained information will identify burn survivors' potential and limitations in realizing the benefits of physical activity tat are important for cardiovascular health, reduced dependency with aging, and improvements in quality of life 2, 15, 16, 100, while serving as the foundation by which exercise-based rehabilitation programs can be implemented to improve the health of severely burned individuals years following the injury.
As a group, severely burned individuals are relatively 'unfit', which likely is a major barrier that prevents them from returning to work and participating in activities of daily living. This project will identify whether a 6 month exercise training program s effective in improving aerobic fitness in severely burned individuals and whether the extent of that improvement is influenced by the amount of burned skin. The obtained information will be extremely valuable to clinicians and burn survivors in identifying burn survivors' potential and limitations in realizing cardiovascular benefits, and associated disease prevention, of physical activity.
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