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IN WHAT ORDER DO WE RECRUIT OUR MOTOR UNITS?
Discussion in 'Training' started by Zillagreybeard, Jul 08, 2021.You must be logged in to reply to this topic.
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IN WHAT ORDER DO WE RECRUIT OUR MOTOR UNITS? ⭕️
“The central nervous system is responsible for the orderly recruitment of motor neurons, beginning with the smallest motor units.” [1]
Henneman’s size principle indicates that motor units are recruited from smallest to largest based on the size of the load but also contraction speed.
Slow twitch, low-force, fatigue-resistant muscle fibers are activated prior to the recruitment of the fast twitch, high-force, less fatigue-resistant muscle fibers.
Larger motor units are typically composed of faster muscle fibers that generate higher forces.[2]
Secondly, the number of muscle fibers controlled by a motor unit increases exponentially with recruitment order: while there are hundreds of thousands of fibers inside a muscle, the number of fibers controlled by each motor unit varies widely, from a handful (low-threshold ones) up to a couple of thousand (high-threshold ones).
Therefore, the amount of force that a low-threshold motor unit can produce is far smaller than the amount of force exerted by a high-threshold motor unit.
What happens when we move light weights to failure?
Just like mentioned above, light loads will recruit low-threshold muscle fiber that exert less force. However, since we’re taking the contraction to task failure, things become a little different:
Quite in fact, due to an increase in effort perception because of fatigue mechanisms happening within the muscle, the central nervous system will recruit high-threshold motor units.
Should I make more posts on muscle fibers, their differences & more..? Let me know in the comment section if you’re enjoying this type of informative content. It truly helps me out. 🤘🏻