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Active and passive insufficiency and why it matters

Make a fist and squeeze your hand as hard as you can. Good! Now flex your wrist towards the palm side of your hand and try again. Now you probably failed to apply nearly as much force as in your first try. Why is that?
In this article we'll explore the definition of passive and active insufficiencies of muscles. We're going to find out how muscles contract optimally, why regular incline bench press barely works the upper chest, how to target the individual heads of the bicep and how this all ties in to further optimise your exercise selection. Hope you enjoy!

How do muscle's contract?
To create an understanding of how muscle contractions become insufficient we need to know how they become sufficient first. A sufficient muscle contraction is a contraction where the myosin and actin filaments can comfortably slide over each other. This means that there is an optimal amount of distance the actin filaments can travel to facilitate an optimal contraction. On the opposite end of this spectrum muscles become insufficient. This can happen in two ways:
  • A muscle filament is lengthened and the actin and myosin filaments are too far apart to facilitate a contraction. This is called passive insufficiency.
  • A muscle filament is shortened and the actin and myosin filaments ar too close to each other to facilitate a contraction. This is called active insufficiency. 
And in between the optimal and insufficient is a whole lot of grey area you can use to your advantage.  

For instance:
Let's take the bicep muscle as an example. 
When a preacher curl is performed, the long head of the bicep is made actively insufficient. The function of the long head is anteflexion (and elbow flexion of course). When the upper arm is passively anteflexed (as in a preacher curl) it causes the actin and myosin filaments to move towards each other, leading to a suboptimal contraction. Now when you flex the elbow, the short head of the bicep -which is in a more optimal position- will have to work harder to flex the elbow. Thus leading to higher activity of the short head of the bicep. 
When the upper arm is retroflexed (elbow behind the body) as in a lying incline dumbbell curl, the short head becomes passively insufficient and the long head of the bicep can contract more optimally.

So how does this work in the chest area?

When looking at the chest, you can roughly divide the chest in to three area's. The Clavicular (upper), The Sternal (middle) and Abdominal (lower) chest. These three parts can be identified not just by where they originate but also by the direction of their fibres.
Try to answer this question before reading on:
Which fibers will become actively insufficient (myosin/actin filaments too close to contract) when the you internally rotate the upper arm (thumbs facing inward)?

Yes, the upper chest. So by doing an incline barbell bench press you are internally rotating the upper arm and not allowing an optimal contraction for the upper chest.
Now how to solve this:
You can do neutral grip bench presses with either dumbbells or a Swiss bar.  If you want to go more extreme do bench presses with a reverse grip (thumbs facing outward), this will ensure a full range of motion for your upper chest. 

Now these concepts can be applied to every exercise. If you stand in a very wide squat, your adductors will have to work harder and your glutes wont be able to contract as optimally.
Luckily though, for most exercises there's a happy middle where all muscles can fire more or less optimally. However if you want to focus on using a certain muscle group more specifically the active/passive insufficiency concepts can be a very effective tool.

I hope you enjoyed this, any feedback or questions are most welcome!:)

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