Coach Chris Korfist Breaks Down the Block Start: Position, Shin Angles, and Better Acceleration
A great block start is not just about pushing hard. It is about pushing in the right direction, from the right position, with the right body angles.
In this video breakdown, Coach Chris Korfist walks an athlete through two different sprint starts and explains why one is clearly more effective than the other. What makes the analysis valuable is that the difference is not simply whether the athlete is using blocks. The biggest difference is how the athlete organizes the torso, hips, shins, and foot during the first few steps.
The discussion gives coaches and athletes a practical way to look at acceleration mechanics and understand why a start can feel powerful but still send force in the wrong direction.
Getting the Mass in Front
One of the first things Coach Korfist points out is the athlete’s torso position.
In the better start, the athlete gets the torso farther out in front of the body. This allows the athlete to apply force more effectively in a forward direction.
Korfist explains this through a simple physics concept: where is the athlete’s mass when force is applied?
If the body’s mass is positioned too far behind the point of force application, the athlete may create unnecessary rotation or vertical movement rather than projecting forward.
The better position looks more like a continuous line:
Chest in front of the hips.
Hips in front of the feet.
That alignment gives the athlete a better opportunity to project the entire body forward.
In the weaker start, the athlete becomes more “stacked.” The chest is closer to directly above the hips and the hips are closer to being directly above the feet.
The result is that the athlete begins rising earlier instead of continuing to accelerate forward.
Forward Projection vs. Pushing Up
This distinction becomes especially important during the first two or three steps.
A sprinter can generate a tremendous amount of force, but if that force is directed upward too early, some of the acceleration opportunity is lost.
In the stronger start, the athlete maintains better shin angles and keeps driving forward.
In the other start, the athlete begins pushing upward earlier.
That difference can be subtle when watching a sprint at full speed, but slowing the video down makes it much easier to see.
The question coaches should continue asking is:
Is the athlete pushing forward, or are they already starting to push up?
During early acceleration, the goal is to continue producing horizontal displacement while gradually transitioning toward upright sprinting.
Why Shin Angles Matter
Coach Korfist also focuses heavily on the athlete’s shin angle.
In the better start, the shin continues to drop into a position that allows the athlete to project forward.
The athlete does not simply put the foot into the ground and immediately push away from it.
Instead, the body moves over the foot before force is fully applied.
This creates a much better acceleration position.
The shin angle then reflects the direction in which force can be applied.
If the shin is already too vertical, the athlete is much more likely to push vertically.
If the shin stays angled forward, the athlete has a better opportunity to continue projecting horizontally.
The Ball of the Foot as a Pivot Point
One of the most interesting coaching concepts in the video is the idea of using the ball of the foot as a pivot point or fulcrum.
Rather than immediately pushing from the instant the foot contacts the ground, the athlete allows the body to move forward over the foot.
As the athlete rolls over the ball of the foot, the shin can continue moving into a lower, more favorable position.
Then the athlete pushes.
The sequence becomes:
Contact → roll forward → lower the shin → push.
This is different from:
Contact → immediately push upward.
That small timing difference can completely change the direction of force application.
It also helps explain why two starts that initially look similar can produce very different acceleration patterns.
The Importance of the “Scissor”
Another positive feature identified in the better start is the athlete’s recovery action.
The athlete demonstrates a better “scissor,” with the recovery leg moving forward before the first foot strike.
That action helps reposition the limbs for the next step and can contribute to a more effective acceleration rhythm.
The athlete himself notices this improvement while reviewing the video, which highlights another major benefit of video analysis: athletes can begin learning what effective movement actually looks and feels like.
When athletes understand the visual difference between good and poor positions, coaching becomes much more powerful.
Blocks Do Not Automatically Create a Better Start
Perhaps the most interesting conclusion from the session is that the athlete’s better start is not necessarily the one performed from the blocks.
Coach Korfist makes the point very clearly: based on the mechanics shown in the video, the athlete performing the better free start would likely beat the version of himself coming out of the blocks.
That may sound surprising, but it reinforces an important coaching principle.
Equipment does not create acceleration. Position and force application create acceleration.
Blocks may allow an athlete to generate more force, but if the athlete leaves the blocks in a poor position, that additional force may not be directed effectively.
The goal is not simply to push harder out of the blocks.
The goal is to organize the body so that the force being produced actually moves the athlete down the track.
A Simple Coaching Tool: Resisted Starts
One training method Coach Korfist recommends is resisted acceleration using a band or sled.
The resistance helps the athlete feel the body moving forward over the foot.
Instead of immediately pushing vertically, the athlete can learn to:
- stay projected forward,
- allow the ball of the foot to act as a pivot,
- move the shin into a better angle,
- and then apply force.
This can be an effective way to teach acceleration because resistance exaggerates the need for forward projection.
If the athlete stands up too quickly, the movement becomes much harder.
If the athlete stays forward and uses the foot properly, the acceleration pattern becomes much more natural.
What Coaches Should Look For
When evaluating block starts and early acceleration, several key questions come out of Coach Korfist’s breakdown.
Look at the athlete’s overall body position first. Is the chest positioned in front of the hips? Are the hips positioned in front of the feet?
Then look at the shin. Is the athlete maintaining a shin angle that supports forward projection, or is the shin becoming vertical too early?
Next, watch the foot. Does the athlete allow the body to roll over the ball of the foot before pushing, or does the athlete simply strike the ground and immediately push upward?
Finally, look at what happens to the torso during each push. Does the upper body continue moving forward with the athlete, or does it fall behind as the legs push?
These details can tell you much more about acceleration quality than simply looking at how hard an athlete appears to be working.
Final Takeaway
Coach Korfist’s breakdown demonstrates an important principle of sprint acceleration:
The direction of force is determined by position.
A powerful athlete can still produce an inefficient start if the body is not organized correctly.
Getting the torso and hips projected forward, maintaining effective shin angles, allowing the body to move over the ball of the foot, and timing the push correctly can dramatically change acceleration.
The goal is not simply to create more force.
The goal is to create force that moves the athlete forward.
And sometimes the best coaching breakthroughs come from comparing two movements that initially look almost identical, slowing them down, and identifying exactly why one works better than the other.
Watch the full video above to see Coach Chris Korfist take the athlete through the comparison step by step and explain the details that separate the two starts.