Heya!
One great suggestion that we got from our recent survey was to use this newsletter to keep teaching the tangible basics of joint health.
So today I, Coach Will, want to talk about muscle contraction. Let's start with a definition...
To contract in the muscular sense simply means "to shorten or tighten".
This action is signaled by the brain and is delivered to individual muscle fibers extremely rapidly via our nervous system.
Depending on how the muscle contracts, the brain and/or body is "learning" how to do specific things, and over time and through repetition gets better at doing those things (adaption).
First, we have concentric contraction. This is when muscle fibers slide past each other and the muscle belly effectively shortens (and tightens). This action causes bones to move toward each other, and (often) to counteract gravity. When you bend your elbow, the flow of tissue from your palm to your shoulder is contracting concentrically and the result is your hand comes toward your shoulder (and your bicep bulges). Some other examples include:
the UP of a pull up
the UP of a push up
the UP motion of a squat.
Next, we have isometric contractions. These actions sufficiently tighten or stiffen ("brace") a flow tissue such that it doesn't move often against the resistance of a force (gravity, a heavy, non-moveable weight, etc.).
Isometric contractions predominate in your core, but don't be fooled; they are not just responsible for involuntary postural muscles. We can also use them to great effect to build strength, especially at ranges that are weak or unpracticed.
By removing the complexity of movement, the brain can send more signal to one specific flow of tissue and learn how to "be active" there. We take one area and "power-wash" it with a spot-light, literally driving neural activity to the area.
Finally, we have eccentric contractions. As their name suggests, these muscle actions are a little weird :). As those same muscle fibers begin to slide apart, they resist this slide and effectively slow down the lengthening motion.
Imagine an icepick, dragging thru ice as you slide downhill, or the heat from a rugburn as your butt slips down the stairs. That "heat" very often results in micro-tears to your contractile tissue, aka soreness (which is why eccentric training can often make you the most sore).
This "heat" in the muscle is caused by the active resistance from your tissue-brain team. This happens as you come DOWN from a pullup, push up or squat, or any time bones move apart under active control, or against a load.
In our classes we specifically focus on each of these contractions for specific reasons:
Concentric actions are most complex and demanding, and generally we are weakest at them. That weakness also means a big payoff when we can improve our ability to concentrically contract. Concentric contractions, especially coordinated with other contractions, require lots of "brain practice" to improve; after all, they are responsible for moving us thru the world.
Isometric contractions are tough, but are our best fool for improving the connection of our bodies and brains at specific tissues (especially the weak and/or untrained ones). We can become immensely strong with them, even as we use them to improve our weakest link areas, and we can do it all extremely safely (after all, no bones are moving).
Eccentric contractions essentially are our bodies brakes, our way of slowing ourselves down and controlling our dynamic motion through the world. In the case of a pull up, imagine yourself lowering slowly. This demand has a particular signature (in brain waves) and leaves a distinct mark (sore!!) on our tissue. It's often a final stage of training tissue, in which we can work on and improve our actual resiliency (ability to withstand stressors).
So, as you move around today, I encourage you to occasionally check-in and determine which of your tissues seem to be working, and how.
What kind of contractions are you using as you drink from a bottle? Or open a door? How about when you navigate stairs.
We all deserve to know ourselves, especially the parts that work every day.
As always, we'd love to help answer any questions that come up for you about this--just hit reply and an actual human will get back to you!
Go find your gold, Coach Will