31 Relationship of Mitochondrial Phenotype to Muscle Function and Performance

Skeletal muscle mitochondria are vital for producing sufficient energy to fuel muscle contractions during exercise. Embedded within the inner mitochondrial membrane are 4 separate protein complexes that are responsible for transferring electrons from specific substrates to the final electron acceptor, oxygen. The proton gradient that is formed from the movement of electrons then drives complex V, synthesizing ATP to fuel cellular work. Recent technological advancements enable exploration beyond simple measures of mitochondria, such as density and overall function, to identify how the organelles produce energy. Specifically, high-resolution respirometry allows investigation into the capacity of each of these mitochondrial protein complexes to determine if they are differentially utilized during specific types of exercise. Further, unique profiles of utilization of these complexes may be hallmarks of success within a certain performance discipline (e.g., racing, dressage, western work, or jumping). In recent years, our laboratory has substantially contributed to progress in this area of research. Under 3 specific scenarios we: 1) defined in horses as young as 6-months-old differential utilization of complexes among breeds destined for certain racing distances; 2) demonstrated differential impacts on specific mitochondrial complexes between submaximal and high-intensity exercise training; and 3) identified a signature of mitochondrial energy production in Thoroughbred racehorses as weanlings that correlates with their race performance later in life. Complex-specific skeletal muscle mitochondrial research in horses is its infancy but has substantial promise to be used as a tool to optimize performance and prevent fatigue-induced injury in performance horses. Further, greater understanding of the inter-relationships of mitochondrial energy production, exercise training, management, and feeding protocols will be crucial to ensure horses realize their peak performance potential and to maintain animal welfare during intense training and competition schedules.