Adding Velocity: The Rotational Connection

*Cue dramatic music* 

*Pan to random symbol in the sky*

*Zoom in on Cal’s drawing from a week ago showing that exact same random sign*

*Pan back to Cal staring ominously into the night*

Cal: “It’s all connected…” 

The writers of the show “Manifest” are not so subtly hinting at the interrelatedness of seemingly isolated events, but my wife and I find the over-dramaticized slogan to be hilarious. We’ll find ways to work it into our days sometimes and it always gives us a good laugh. However, the accuracy of that statement for the implications of producing rotational power is, well, powerful… “It’s all connected.”

Movement starts in one joint segment and finishes somewhere else. Every “connection” in the chain serves a purpose. One of the most important, and most problematic, connectors is the thoracic spine. Your thoracic spine sits in between your neck (cervical spine) and your low back (lumbar spine). It’s the part of your spine that your rib cage attaches to and it covers a lot of important internal organs (like your heart and lungs). It’s role in protecting these vital organs means that it’s built more for stability than mobility, but having enough mobility here and not getting completely locked down is important for being a powerful rotational athlete.

Thoracic spine rotation is important for all rotational athletes (baseball, softball, lacrosse, volleyball, golf, quarterbacks, etc.). We’re going to use a baseball pitcher as the example today, but this same exact principle applies to all rotational athletes, whether it’s a volleyball player spiking or serving, a lacrosse player shooting or passing, a golfer swinging, a softball catcher gunning down second, or a quarterback throwing a fade, it all applies.

Being able to rotate both ways is massively important. For a right handed pitcher, being able to rotate to the left allows you to follow through without a lot of side bending. Having too much side bending raises your arm slot, which results in missing high. Being able to rotate right allows for appropriate hip-shoulder separation. Hip-shoulder separation refers to having your hips rotated forward, while your shoulders stay facing the side. From a power production standpoint, this helps out in two separate, but very important ways.

Rubber band man

First, it allows for our elastic forces to get involved. We have two main force generators in the human body: muscular contractions and elastic recoils. When your pelvis rotates forward while your shoulders stay back, you create a stretch in the elastic structures that run diagonally across the front of your body (anterior oblique sling). By placing them under a rapid stretch, you get a subsequent rapid recoil, just like shooting a rubber band. This recoil is incredibly helpful for generating more force, which creates more velocity up the chain. Hooke’s Law tells us that the force produced from an ideal spring is directly proportional to the stiffness of the object (k) and the amount of deformation (stretch) of the object (F = k * Δx). So, if you have no thoracic spine rotation, then you have no hip-shoulder separation, no stretch, and no subsequent recoil. No recoil means no gas is being thrown.

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Link-up

The second way that hip-shoulder separation helps with power production is a bit nerdier: kinetic linking using the summation of speed principle. This segment is a bit dense, so if you want a simpler explanation you can skip to the last paragraph of this section. 

Kinetic linking refers to the process of transferring and amplifying kinetic energy from one body segment to another. It operates under the premise of the law of conservation of momentum: the total momentum within a system is constant. Momentum is just transferred from one place to another, it isn’t destroyed. Momentum is equal to mass multiplied by velocity (p = m*v). So, the two components of momentum are mass and velocity. If you increase either one of those variables, then momentum increases. Importantly, because of the law of conservation of momentum, if one of these variables decreases, the other will increase to compensate (assuming no forces outside the system are interfering).

Our powerful movements, like throwing, typically originate with the larger, proximal segments (like your hips and core) and are transferred to the smaller, distal segments (shoulder → elbow → wrist → fingers). Because we are going from larger segments with high mass to smaller segments with low mass, in order to conserve momentum, velocity has to increase from one segment to the next. Furthermore, the summation of speed principle tells us that this transfer of energy is optimized if the distal segment begins rotating at the moment the proximal segment has reached maximal angular velocity. This allows us to amplify the speed from start to finish by initiating the right segments at exactly the right time- which is why thoracic spine rotation is important. 

If you can’t separate the hips and shoulders, then you’re going to rotate early and not give the lower segments enough time to reach peak angular velocity before initiating rotation at the next segment up the chain. This significantly reduces the velocity that you’re going to end up with at ball release.

Test it

In order to actually access this hip-shoulder separation on the field, you need to know if you even have the physical capacity to rotate. That’s where the Locked Lumbar Rotation Test can come into play. You can see a clear distinction between the spine of someone who throws a 95 mph fastball and a guy who stopped rotational sports when he was in elementary school. Check out the video to get an idea of if you need to start addressing some rotational deficits: