Joints and muscles...they are pretty important when it comes to exercise and hopefully now you have a good grasp on what they do and the influence they have. Today we will take everything a step further and discuss a few common exercises and break them down from a joint and muscle perspective.
The main strength training exercise we will look at today will be….
I could spend far too long discussing the squat from a biomechanical, physiological, and neuromuscular perspective, but to spare you from all of that exciting info we will keep it simple. If you are interested I highly recommend this guide by Greg Nuckols. It’s goes VERY in depth. But today we are going to look at our joints and muscles and the influence they have specifically during the squat.
Let’s break down the squat’s motion or movement. We will analyze a bodyweight squat for simplicity:
We have the top position; straight legs and standing up tall
You begin to lower towards the ground until you hit the bottom position
You come back up to the top position (As seen below)
So, let’s look at the role of our joints and muscles! We already know muscles have one job, which is to contract. Joints are the connection of bones and create an axis, which is how we are able to fold during the squat. The joints we will look at are the ankle, knee, and hip (not that those are the only joints involved).
Here is what is happening during each position:
Specific muscles that influence the hip, knee, and ankle are co-contracting to maintain the top position. The contraction is ‘orchestrated’ by the brain and very precise to that position.
Once you start to lower, the muscle around each joint is now responding to the change in position (new external force or torque loading), and creating the necessary contraction (eccentric/concentric or lengthening/shortening) in response to that new torque loading and what your body is trying to do (go up/down).
That change in contraction occurs all the way through the range, from top to bottom.
Pretty fascinating that your body and brain is able to manage all of that in a short amount of time (the time it takes you to go down then back up).
Now that you have an idea of what’s going on during the different positions of a squat, let’s take a look at what is happening from a challenge or stimulus standpoint (or better yet the resistance) at each position. Let’s specifically look at the hip and knee:
We can see that the resistance (represented by the green line) goes straight through the joints (hip and knee) at the top position. This means that there is little to no challenge since there is no external torque loading at the hip or knee...remember torque is not just the amount (pounds on barbell or bodyweight), there is also a distance component (also known as a moment arm).
As you begin to lower or fold to the bottom position, that distance from the axis begins to change. This means that the muscles around the joints (hip and knee) must create an internal force or torque in response to the external force or torque. Also note that the distance is further from the hip than the knee, meaning the hip musculature must deal with more resistance. (Disclaimer: this is just one figure, each person is built very differently and has their own unique structure. This will determine the foldability of that individual….please watch this if you’d like to know more)
On the way back up, the external torque begins to decrease as you begin to straighten the legs.
So why does this matter? Because squats often are glorified as ‘the best’ or the all encompassing exercise, but as we can see that is not the case. Again, always ask yourself for who and what’s the goal, but if someone wants to strengthen the lower extremity (hips,knees, ankles), there are a few things the squat doesn’t do:
There is no challenge in a knee extended and hip extended position (the top). You could have a lot of weight on your back and hold it there with minimal effort. Those could potentially be important positions depending on the individual on their goals. This means that a 2nd or 3rd exercise would need to be added to challenge those specific positions.
The bottom position is where the challenge is the hardest/heaviest, meaning you’re limited to the amount of weight you can lift from that position. That could potentially limit the challenge through the rest of the range (middle and top). Try this: break up your squat into a bottom and top; using different weights for both...less for bottom, more for top. This should challenge each portion of the range appropriately.
This should bring some perspective into how the resistance may change throughout an exercise, how the weight you choose isn't the only factor, and how your joints/muscles respond to that resistance (specifically in a squat). Next week we will analyze the chest press.
Purvis, Tom. Resistance Training Specialist. Squats Part 1: Foldability and Proportions. Retrieved from YouTube.com.
Nuckols, Greg. How to Squat: The Definitive Guide. Retrieved from Strongerbyscience.com.