BlockStart Biometrics: Video Analysis and Coaching Guide

COCO-17 keypoints, confidence-gated angles, and event-based coaching cues.

The report is not for decoration. It is a working checklist. Start with the red cards, keep what is already good, and re-test after a focused training block. That is how you move your first 10 meters.

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Video recording guidelines for block start analysis

Part 1: How To Record The Block Start

Good recording is mandatory. Poor angles give poor numbers.

Use the checklist in the graphic and follow these five steps every session:

1. Side-view, landscape: hold the phone horizontally and place it at 90 degrees to the lane. Keep the athlete head-to-toe in frame.
2. Steady footage: use a tripod on stable ground. Handheld footage introduces shake and corrupts angle tracking.
3. Camera settings: minimum 60 fps at 1080p. Higher frame rates help, but do not sacrifice clarity and lighting.
4. Bright lighting: daylight is best. Indoors can work if the athlete is clearly separated from the background.
5. Start in set: begin recording only once the athlete is motionless in set. Do not include the pre-start routine.

Keep recording conditions consistent across test days. If camera angle or lighting changes, comparison data becomes less useful.

Block start report card and metric interpretation

Part 2: Interpret The Report Card

Sample report: Direction Left, Start Score 74/100.

Start score 74 is a solid baseline with angles to tighten. Read the red FIX cards first, then reinforce what is already green. That is the order.

Key Moments

Set 0.192s | First Move 0.367s | Clearance 0.725s | Touchdown 0.900s

These timestamps frame the whole start sequence and anchor every event-based metric.

Front Knee Angle (Set)

98° GOOD | Target 90-100°

Front leg loading angle in set. Keep block spacing so the front leg preloads without collapsing.

Rear Knee Angle (Set)

118° GOOD | Target 110-130°

Rear leg push window against the back block. If this drifts, adjust rear block distance.

Projection Angle (Clearance)

34° FIX | Target 40-45°

If projection is too high, horizontal speed is lost. Stay lower and push back through the blocks longer.

First-Step Shin Angle

58° FIX | Target ≤ 45°

High shin angle usually means a stepping action. Keep shin low and attack backward into the track.

Overstride Index

0.05 body GOOD | Target ≤ 0.10

First-step ankle landing distance relative to the hip. Lower values preserve horizontal force.

Set Position Metrics

Shoulder Drop 39.9% FIX | Trunk Angle 22° GOOD

Shoulders should be slightly lower with pressure through both hands. Keep the set posture repeatable.

Initiation Metrics

Onset 0.175s GOOD | Arm Split 0.192s FIX

Reaction is acceptable, but arm split is late. Arms and legs should launch together, not in sequence.

Clearance Metrics

Trunk 9° FIX | Hip Drive 1.54 body/s GOOD

Hip drive is there, but posture rises too soon. Keep chest down through clearance to carry force forward.

Knee Extension Rates

Front 339°/s GOOD | Rear 137°/s OKAY

Front-side extension is strong. Rear side is close to target and should be cleaned up with block spacing and push mechanics.

Touchdown Metrics

Trunk 22° FIX | Clearance-to-TD 0.175s GOOD

Do not stand up early at touchdown. Keep projecting forward over the first steps.

Trend Metrics

Rise Time to 60° N/A | Rise Time to 75° N/A

N/A means this clip did not provide enough clean frames for that trend. Re-test with cleaner capture.

Coaching Priorities

Take the top three red cards and address them immediately.

The report card auto-generates coaching cues, but you still need discipline in how you apply them. Fix one or two constraints, then test again. Do not try to change everything in one session.

1. Optimize Projection Angle

Issue: projection at clearance is below target in this sample.

Cue: stay low and push back longer before rising. Keep head neutral and do not pop up off the blocks.

2. Improve First-Step Shin Angle

Issue: first-step shin is too high, which turns the step into a brake.

Cue: keep shin low and attack backward into the track under the hip, not out in front.

3. Accelerate Arm Split

Issue: delay from first movement to aggressive wrist acceleration.

Cue: split the arms sooner so torso and legs launch as one unit at the gun.

Additional Cues The App Can Surface

Shoulder drop in set, trunk angle at clearance, and trunk angle at touchdown are all tied to maintaining horizontal intent through the first steps.

Coach's rule: keep what is green, fix what is red, and verify with another clip. Let the data confirm your cueing before moving on.

Block start coaching points and performance summary

Session Checklist

Use the same camera position, same block setup protocol, and same testing distance each time. Consistency is how you make the trend data trustworthy.

Record multiple starts and keep only clean, side-on clips where the full body is visible.
Prioritize red FIX cards first, then confirm improvements through re-testing.
Keep coaching cues simple during training blocks: one technical cue per rep block is enough.

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