Type I (slow-twitch, slow oxidative) muscle fibers derive their energy primarily from aerobic energy pathways.

Quick Scoop

  • The muscle fibers that rely most on aerobic (oxygen-using) metabolism are Type I, also called slow-twitch or slow oxidative fibers.
  • These fibers are rich in mitochondria and myoglobin, which support long-duration, lower-intensity activities like distance running or maintaining posture.

Why Type I Is The Answer

  • Type I/slow oxidative fibers mainly use aerobic respiration to make ATP, so they can sustain contractions for long periods without fatiguing quickly.
  • In contrast, fast glycolytic (Type IIx/IIb) fibers rely mostly on anaerobic glycolysis, and fast oxidative (Type IIa) fibers mix aerobic and anaerobic pathways rather than depending primarily on aerobic ones.

So, for the question “which type of muscle fiber derives its energy primarily from aerobic energy pathways?”, the best answer is: Type I (slow-twitch, slow oxidative) fibers.

TL;DR: Type I slow-twitch (slow oxidative) fibers are the ones that get most of their energy from aerobic energy pathways.

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