2024.04.01 – Are You Training All of Your Muscles?

I suspect that the first thing that popped into your head was trying to make a list of all of your muscles, and figuring out if you do exercises that strengthen all of them:

• Bicecps – curls
• Triceps – skull crushers
• Gluts – deadlifts
• Quadriceps – lunges
• Abdominals – planks
• and so on

If that is what you did, then sorry to say I tricked you 😉

What I was referring to was all of the parts within a muscle.

One example is that your muscles have several different types of fibers within them – very much like a rope has lots of different individual fibers that combine to make up one larger rope.

So, within a muscle like your biceps, you have a ton of individual fibers that combine to make up the muscle.

Now, unlike a rope, not all of these fibers are the same.  They exist on a continuum, but for simplicity sake we’ll call some of them “slow twitch” and others “fast twitch” fibers (you can break them down into many more categories than that – this is overly simplified).

Different muscles contain different proportions of fast twitch vs. slow twitch fibers.  Some muscles might be about a 50/50 split, some might be have proportionally more slow twitch, and others might have proportionally more fast twitch.  Also, for a given muscle (let’s say your quadriceps) one person might have a certain percentage of slow twitch fibers, and a different person will have a different percentage – there can be a lot of individual variance.

The good news is that in spite of this individual variance the way you train to improve them does not change.

Your body likes to preserve its resources – basically it is lazy 😂 So, when you start to do any activity it always starts by using the slow twitch fibers first because they cost your body less energy.

In fact, a related term (although not interchangeable) to “fast twitch” fibers is “high threshold motor units.”  The specifics there are not super important for now, but essentially it means that a high threshold must be met in order to recruit and activate your fast twitch fibers.

This threshold is met one of two ways: 1) heavy weights or 2) fast movements (like jumping or sprinting).

So, if you want to work all of your muscles then you cannot only do cardio, nor can you only do light weights for high reps.  You must also train your fast twitch fibers, which means you need to lift heavy weights and/or do high speed movements.  

More info to come on this later this week.  Between now and then, go lift something heavy 💪

-Tony