1. Figure 2 Muscle structure
Figure 2 | Muscle structure. Type I fibres (blue) have high mitochondrial density, high levels of myoglobin, and a high number of associated capillaries, and thus type I fibres have high oxidative capacity. Type I fibres are associated with an improved resistance to fatigue and increased exercise capacity. Type II fibres (red) have high levels of ATPase and creatine kinase activity, and high levels of anaerobic glycolysis (glycolytic capacity). Muscle fibre types can transform in response to external stimuli such as exercise. Low physical activity leads to slow-to-fast twitch transformation, and high physical activity promotes fast-to-slow twitch transformation. During ageing, type II fibres are more susceptible to atrophy than type I fibres.
von Haehling, S. et al. (2017) Muscle wasting and cachexia in heart failure: mechanisms and therapies
Nat. Rev. Cardiol. doi: /nrcardio