Why do muscles ‘shudder’ when lifting weights?
In: Biology
Muscle fiber recruitment (activation) is not equally precise throughout a muscle’s range of force output. When we perform fine manipulation, the motor units recruited fall within a range of high resolution but low force. These motor units each have relatively few muscle fibers. When we lift near our max force output, the motor units recruited are larger and less precise. These have relatively many muscle fibers per unit. Look up Henneman’s size principle for more info.
Shaking near max force output is due to the on-off switching of big motor units as your body tries to do things related to load balancing and fatigue management.
Each muscle cell is one really long cell that runs the entire length of the muscle. And anyone muscle cell can be either relaxed or flexing, but not any combination of the two.
So in order to modulate how much Force a muscle is generating, we have to change the number of muscle cells that are firing.
But while we are lifting heavy things, inevitably some of our muscle fibers get tired and wear out, so they stopped firing and then we have to have another one jump in and replace it. This means that our brain has to do a lot of work to constantly be compensating for changes in the muscle and which fibers are firing, and that work takes a little bit of time, which makes our muscles wobbly when we are using them near their limits.
My muscles don’t shudder when lifting weights. Am i doing something wrong?
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