Understanding Elbow Extension in the Quarterback Throw

When analyzing a quarterback’s mechanics, a key piece of data is the angle of elbow extension/flexion in the throwing arm. In our biomechanics reports, this is shown as the solid blue line on your throwing arm joint angle graph found on page 3.

What You’re Seeing on the Graph

On the x-axis (horizontal), you’ll see the timeline of the throw from start of throw through follow through:

• The first vertical line represents foot strike, when the front foot hits the ground.
• The second vertical line marks maximum external rotation (MER) when the throwing side shoulder is at its furthest layback.
• The third vertical line indicates ball release.
  

On the y-axis (vertical), we’re measuring degrees of elbow angle. This is essentially, how bent or extended the arm is at each point in the throw.

How Elbow Angle Works

The elbow is a hinge joint, which moves between flexion (bending) and extension (straightening).

• 0° = full extension (arm straight).
• 180° = full flexion (arm completely bent).
• Most throws occur between 30°–120°, depending on phase and player.
  

When the blue line on your graph drops, that indicates extension. When the line rises, the elbow is flexing or bending.

Typical Movement Through the Throw

A clean throwing pattern usually looks something like this:

1. Setup & Load Phase: The elbow begins slightly flexed, often around 100–110°.
2. Pull Phase (into Foot Strike): As the QB starts to pull, the elbow begins to extend.
3. Maximum External Rotation (Layback): As the arm lays back, the elbow naturally flexes.
4. Acceleration & Ball Release: The elbow rapidly extends as the hand comes forward. Ideally, you’ll see around 30–40° at ball release. While you’ll rarely hit 0°, getting under 40° indicates excellent extension and whip.

What to Watch For

• Too Long (Over-Extension):
  If the blue line dips below 50° during the pull phase , the arm may be “getting long” behind the body. This can reduce efficiency and slow down release time.
• Too Much Flexion:
  If your elbow angle spikes above 100° during layback, it’s likely collapsing too much, which can reduce velocity and put excess stress on the elbow.
  

Key Takeaway

Efficient quarterbacks extend and flex their elbow at the right times. The goal is a smooth transition throughout the sequence.

Understanding this graph helps you pinpoint whether your throwing arm is working with your body or lagging behind it. That’s a major factor in both velocity and arm health.