eli5 why do muscles get tired after holding the same position for an extended period of time?
In: 169
Some don’t! You have two types of muscles in your body:
– Smooth muscle
– Skeletal Muscle
Smooth muscles are all the muscles you don’t control and these ones don’t really get tired! These include the bowls, stomach, anus, heart and a few others. Think: your anus muscle stays clenched 24×7 and it never gets tired! (Thank god! Could you imagine how messy that would get). Likewise your heart very rarely gets tired unless you have an underlying condition, or you’re doing extreme endurance training.
Skeletal muscles are the ones you’re thinking of and the muscles you can consciously control. They do get tired and usually via two main mechanisms: neural fatigue and metabolic fatigue. The system that sends signals (neurons) get tired from signalling the muscles to contract and the muscles, consuming energy, get tired from contracting (metabolic fatigue).
Both forms of fatigue are underpined by the same basic problem: not enough energy to fuel the work OR too much waste which is interfering with using incoming energy (ATP).
It’s a lot like a car. A car uses fuel + air (aka ATP for muscles) and produces exhaust gas (lactic acid and other byproducts for muscles) to make power. If the exhaust gets blocked or restricted and the exhaust gas can’t clear the engine, power is lost because exhaust gas interferes with the fuel + air mixture. You do this long enough the car will stop. Likewise if you don’t have enough fuel in your tank because you’ve been driving for a long time (aka using your muscles for a long time) your car will also stop.
Latest Answers