Fastoxidative

Fastoxidative is a term used in biology and exercise physiology to describe a specific type of muscle fiber. These fibers, also known as Type IIa or intermediate fast-twitch fibers, possess characteristics that fall between slow-oxidative (Type I) and fast-glycolytic (Type IIb or IIx) fibers. Fastoxidative fibers have a relatively high capacity for aerobic respiration, meaning they can produce ATP efficiently using oxygen. This oxidative capacity contributes to their resistance to fatigue, though not to the same extent as slow-oxidative fibers.

Despite their oxidative capabilities, fastoxidative fibers also have a significant capacity for anaerobic glycolysis, allowing them to generate ATP rapidly for short bursts of intense activity. This dual capability makes them versatile. They are recruited for activities that require a combination of strength and endurance, such as middle-distance running or swimming. Their contraction speed is faster than slow-oxidative fibers but slower than fast-glycolytic fibers. The presence and proportion of fastoxidative fibers in an individual's muscles can be influenced by genetics and training. Endurance training, in particular, can enhance the oxidative capacity of fast-twitch fibers, potentially shifting them towards a more oxidative phenotype.