The classification of muscles is dependent on their pathway and the speed of that pathway to creating ATP (adenosine triphosphate), which is the fuel for muscle contraction.

Your muscle is made up of smaller muscle fibers that can be broken down into three types:

SLOW OXIDATIVE (SO)

(Slow Twitch) – Slow contractions & require more oxygen & glucose (aerobic respiration) to produce ATP (adenosine triphosphate) for long periods of time.

Example: Endurance muscles: maintain posture, produce isometric contractions, stabilize bones & joints

FAST OXIDATIVE (FO)

(Fast twitch Type 2A) – Fast contractions & primarily use aerobic respiration (oxygen & glucose) but can also use anaerobic (glycolysis) which means they can fatigue faster than SO fibers.

Example: Everyday/Light movement: walking, laundry, life.

FAST GLYCOLYTIC (FG)

(Fast twitch Type 2B)- Fast contractions mainly use anaerobic glycolysis leading them to produce more power but fatigue faster.

Example: Power movements: Sprints, jumps, Olympic lifts

Designing an optimal plan should include development of all of these muscle types regardless of your goal. The reality of it is that there is no ONE muscle fiber type in what we call a “muscle”. They are all a combination of fibers, with a large majority of them being one type. So to truly develop any muscle, all of these energy systems need to be applied.