changes number in muscle, and we will discuss those in detail in the next few pages. However, a portion of these adaptations is related to factors external to the muscle. This in Fib needs to be stated at the beginning of this section because, while we focus on the link between changes It is w shift in skeletal muscle and performance, there is evidence that some improvements in performance occur rap Chap. idly and might precede structural or biochemical fiber t changes in skeletal muscle (36). This suggests that initial metabolic adaptations to endurance train might consist of changes in the nervous system or isoform neural-hormonal adaptations, which are followed by able t biochemical adaptations in muscle fibers. In the introduction to this chapter, we mentioned for that the increase in submaximal performance follow- crease an endurance training program was due more to biochemical and structural changes in the trained skeletal muscle than to an increase in VO2 max. The shift typical changes include increases in the percentage of slow muscle fibers (i.e., fast-to-slow fiber type shift), number of mitochondria in fibers, added ability for slow muscle to metabolize fat, improved muscle antioxidant capacity, and increased capillary density (39)
Indeed, these training induced changes in muscle primarily determine the overall physiological responses and to a given submaximal exercise bout. Let's discussion with an overview of endurance training dap induced changes in muscle fiber types and capillary number in skeletal muscle the