What is the difference between slow and fast twitch muscle fibers and how do you train each?


What is the difference between slow and fast twitch muscle fibers and how do you train each?

In: Biology

Slow twitch muscles are designed to handle long periods of steady-ish state activities, walking for example. They have a bunch of little power generators inside them called mitochondria which produce the energy needed to flex a muscle (ATP). These fuel contraction units (myofibrils) which is how you move. The key here is that they don’t require a huge amount of energy because they are contracting somewhat slow, plus there’s a large amount of energy production nearby, so you get muscles that can handle a lot of steady state movement.

Fast twitch handles the overload. Slow twitch muscles always contract first, and when they hit a wall strength wise, fast twitch activate to pick up the slack. They hit HARD and FAST and all at once (many of them will hit at once where a slow twitch muscle doesn’t), so they can overcome whatever is happening. Good if you need to carry something up a flight of stairs, BUT there’s a big trade off here – the energy/recovery efficiency of fast twitch muscles is atrocious compared to slow twitch (both head through glycolisis but slow twitch proceeds through the krebs cycle which can generate a huge amount of energy compared to glycolysis alone). They also have a lot more myofibrils but relatively few mitochondria, plus other structural things, which means they hit with a lot of fury and then they need some serious down time to recover the damage.

An additional point which will head into training – muscles aren’t 100% committed to a type. There is carryover – a type 1 muscle fiber will behave like a type 2a with sufficient weight training for example. You aren’t held strictly to a column, although genetically you are going to be dedicated to a general trend (try doing a standing vertical jump, in untrained individuals this is one of the more predictive measures of athletic performance).

Training is straight forward all muscle fibers will head in the direction you tell it to. Do a lot of cardio and all of your muscles will add in mitochondria, the slow twitch will just get even better at it. Do a bunch of weight training and everything will add myofibrils, with the fast twitch getting even stronger.