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Experiment 1: Bench Press Front View Analysis

April 23, 2026 · 5 reps kept · 15 frames sent · gpt-5.4

Approach

  1. 1. Estimate body pose

    • Record video of bench press.
    • Produce COCO-17 keypoints for each frame, including shoulders, elbows, wrists, hips, knees, and ankles.
  2. 2. Extract frames from video

    • Select bottom, mid-point and top of lift.
  3. 3. Generate coaching

    • Send each rep's frames to GPT 5.4 for feedback.

Coaching

Overall

  • Bar stays mostly level early, then athlete-right rises slightly faster and finishes a touch higher from rep 3 onward.
  • Grip looks close to even and bar path is centered enough, but athlete-left wrist is consistently more extended and less stacked over the elbow.
  • Bottom position shows mild asymmetry: athlete-right elbow flares a bit more while athlete-left stays slightly more tucked.
  • Fatigue is visible late in the set with more uneven mid-range press-out; cue even leg drive and push both hands up at the same speed.
  • Main fixes: stack athlete-left wrist harder, keep elbow flare matched side-to-side, and pause or tempo work to clean up the sticking region symmetry.

Rep 1

TOP rep 1 (9.2s)
TOP rep 1 (9.2s)
MID rep 1 (10.1s)
MID rep 1 (10.1s)
BOTTOM rep 1 (11.0s)
BOTTOM rep 1 (11.0s)

Mostly symmetrical rep. Bar is nearly level through all three frames; athlete-left wrist is more bent back at top/mid, so focus on stacking that wrist directly over the elbow.

Rep 2

TOP rep 2 (11.9s)
TOP rep 2 (11.9s)
MID rep 2 (12.3s)
MID rep 2 (12.3s)
BOTTOM rep 2 (12.8s)
BOTTOM rep 2 (12.8s)

Still controlled, but mid/bottom show athlete-right elbow slightly wider and athlete-left a bit more tucked. Keep the same touch point, but match elbow flare and maintain straighter athlete-left wrist.

Rep 3

TOP rep 3 (13.7s)
TOP rep 3 (13.7s)
MID rep 3 (14.2s)
MID rep 3 (14.2s)
BOTTOM rep 3 (14.7s)
BOTTOM rep 3 (14.7s)

First clear uneven press: at mid/top the athlete-right side gets up a little faster and finishes slightly higher. Cue 'press evenly off the chest' and keep athlete-left wrist/elbow stacked to stop that lag.

Rep 4

TOP rep 4 (15.6s)
TOP rep 4 (15.6s)
MID rep 4 (16.4s)
MID rep 4 (16.4s)
BOTTOM rep 4 (17.3s)
BOTTOM rep 4 (17.3s)

Asymmetry increases in the sticking region; athlete-right again leads while athlete-left lags with more wrist extension. Bottom position is still close, so the fix is a more even drive out of the chest and firmer athlete-left wrist position.

Rep 5

TOP rep 5 (18.4s)
TOP rep 5 (18.4s)
MID rep 5 (19.3s)
MID rep 5 (19.3s)
BOTTOM rep 5 (20.2s)
BOTTOM rep 5 (20.2s)

Most fatigued rep: bar remains centered, but athlete-right leads through mid and reaches lockout a touch sooner and higher. Athlete-left wrist is again the weaker stack, so prioritize neutral wrist and synchronized press timing.