Rapid Stability in Legs & Spine
Rapid Stability - The Most Important Factor in Vertical Jump Height & Speed?
While not typically understood, my bias is that rapid stability may be the most important factor not only in vertical jump training for sports, but in improving sports performance and reducing injury risks at the same time for all explosive sports movements.
So stability simply means control and we may use terms interchangeably.
Stability as related to vertical jump is related to the stability or control of the ankles, knees, hips and spine as you jump and land.
There are muscles around the ankles knees, hips and spine that are called stabilizer muscles.
These muscles are small and lie deep in the body, surrounding most all the joints but for this conversation we will focus on the joints of the ankles, kness, hips and spine.
The stabilizers basically connect two bones together.
Stabilizers Hold Bones Together
The stabilizers have a simple job which is to hold the joints of the ankles, knees, hips and spine together as these joints move, bend and straighten.
How Muscles Work in Jumping
Downward Movement of the Body
As an athlete prepares to jump, they drop their body down towards the ground first.
This action bends the ankles, knees, hips & spine joints.
Big Jumping Muscles
When these joints bend, the big jumping muscles of the calves, hamstrings, quadriceps, glutes and back stretch like rubber bands.
This critically important stretch, loads these elastic muscles.
This stretch stimulates these muscles to contract and move back in the opposite direction, shortening fast and generating a great deal of force which rapidly straightens the ankles, knees, hips and spine.
Then the feet are pushed into the ground and the forces from the big jumping muscles essentially pressing the feet down into the ground.
The ground doesn't give way and these downward forces of the feet and body into ground essentially pushes the body up vertically, in the opposite direction, up into the air.
Stabilizer Muscles in Jumping
So as the ankles, knees, hips and spine bend, as the body lowers in preparation for the jump, the stabilizer muscles are working to hold these joints together.
This is needed because the jumping muscles are pulling hard on leg and spine bones and these forces would pull the joints apart if the small stabilizer muscles weren't also working hard to hold these joints together (as the body lowers and then moves back up vertically as the athlete jumps up off the ground).
Avoiding Lateral Movements
If it wasn't for the joint stabilizer muscles working to stabilize the joints of the ankles, knees, hips and spine, the legs and body would move sideways or laterally. This would negatively impact the vertical jump, reducing both the height and speed of the vertical jump.
This is super important!
We don’t just want stability or control of these joints, but we need stability really, really fast!
If the stabilizer muscles contract or work slowly, the big jumping muscles, as they contract very forcibly, could cause injury to these joints (the ankles, knees, hips and spine).
Understand that these small stabilizer muscles need to actually go to work before the big muscles start to stretch or shorten (contract). More importantly, the stabilizers have to contract quickly to start working before the big muscles fire and created their huge forces on the bones & joints.
So, these small stabilizer muscles can't just take their time contracting to hold these joints together. They have to fire fast to already be working when the big muscles go to work!
What Goes Up...
Are the stabilizer muscles done once the body leaves the ground in a jump? NO!
They're still working while the body is in the air, still holding the joints together.
When the body returns to the ground the weight or load on the ankle, knees, hips and spine can be 3-4 or maybe even 6-8 times the weight of the body.
It is extremely important to understand that the stabilizers are likely working their hardest as the body returns to the ground when all these huge forces are on these joints.
Stabilizer Training, Conditioning & Injury Prevention
When the stabilizers are conditioned properly, they will work to stabilize or hold the joints together, protecting the joints from injury.
Note that many strength programs don't focus on the training & conditioning of the stabilizers. This actually reduces vertical jump height, speed and increases injury risk!
Ground Contact Time
There’s a technical concept called “ground contact time” in jumping and sprinting that applies here so let’s touch on it.
If you’re training to jump high and fast, the longer your feet are on the ground, the slower and lower you will jump.
Reducing Ground Contact Time
So the objective is to reduce how long the feet are in contact with the ground to jump faster & higher.
Stabilizers & Ground Contact Time
The better you are at quickly stabilizing the ankles, knees, hips and spine, the less time your feet are on the ground (which mean’s less ground contact time) and the faster you will move, and the faster and higher you will jump.
Stabilizer Training & Conditioning
In simple terms, make sure the stabilizers are well trained and conditioned as they have to start working fast (before the jump starts) and have to continue to work as the athlete leaves the ground, moves through the air and then they have to work even harder as the body returns to the ground!
They need to be trained to be fast, explosive, strong and must have endurance to hold their contraction for a long period of time.
If that's not enough, they must be prepared to do that over and over again as an athlete, specifically a volleyball athlete in this case, jumps over and over in a match or worse in a 3- or 4-day event.