Backpack Load and Spinal Curvature

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Backpack Load and Spinal Curvature

ISEF Category: Biomedical Engineering

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Subcategory: Biomechanics  ·  Difficulty: Intermediate  ·  Setup: Home Setup  ·  Time: 1 to 2 Weeks

The Hook

By the time the average high school student graduates, they have walked thousands of miles under a backpack. The load bends the spine forward and changes how muscles pull on lumbar discs. You can measure that bend with your phone and predict the moment on the lower back with a simple stick figure.

What Is It?

Pose estimation finds body landmarks in a photo or video. MediaPipe and similar libraries give you shoulder, hip, and ankle positions in pixels. With a height calibration, you convert pixels to real centimeters.

A 2D rigid-link model treats the body as a chain of stiff segments connected by joints. Backpack weight pulls the torso forward, and the lumbar joint resists with a moment. The moment is mass times the horizontal distance between the load center and the lumbar joint.

A short, anonymous survey about backpack weight and self-reported back pain links the biomechanical measure to a real outcome. The combination of pose-derived curvature, predicted moment, and survey response forms a complete pipeline.

Why This Is a Good Topic

Backpack ergonomics is relatable, ethical to study with informed consent, and amenable to a clean within-subject design. You will learn pose estimation, free-body diagrams, and survey design.

Research Questions

  • How does backpack weight as a fraction of body weight change trunk-flexion angle?
  • What is the effect of pack position (high vs. low) on lumbar moment?
  • Does sustained loading increase forward lean within a 10-minute walk?
  • To what extent does shoulder-strap padding shift posture?
  • Which load fraction predicts self-reported back-pain symptoms?
  • How does single-strap carry change asymmetry vs. double-strap?
  • What is the effect of pack contents distribution on calculated moment?

Basic Materials

  • Smartphone with stand for video capture.
  • Bathroom scale to measure body weight and pack weight.
  • Tape measure for height calibration.
  • Backpacks of varying capacity.
  • Standardized objects to load the pack.
  • Informed-consent form and short survey.

Advanced Materials

  • IMU sensors taped to spinous processes.
  • EMG sensors on paraspinal muscles.
  • Pressure-mapping insoles.
  • Motion-capture lab access.

Software & Tools

  • MediaPipe Pose: Extracts landmarks from each frame.
  • Python (NumPy): Computes joint angles and moments.
  • ImageJ: Provides ground-truth angles for a subset of frames.
  • Google Forms: Collects the back-pain survey.

Experiment Steps

  1. Lock a fixed camera position and height before any recording.
  2. Calibrate pixel-to-centimeter scaling with a known-length reference.
  3. Decide load levels as fractions of body weight and the order of conditions.
  4. Plan controls (no pack, empty pack) and a baseline survey.
  5. Run a within-subject protocol with rest periods between trials.
  6. Compare measured moments to published lumbar moment ranges.

Common Pitfalls

  • Recording subjects against cluttered backgrounds, hurting landmark accuracy.
  • Failing to randomize load order, letting fatigue confound results.
  • Skipping IRB-light ethics review for the survey.
  • Treating one frame per condition as the angle instead of averaging a window.
  • Mixing one-strap and two-strap conditions without controlling for strap padding.

What Makes This Competitive

Add subject-wise data splits, calibrate pixel-to-centimeter scaling with a checkered reference, and compare your predicted lumbar moment to published values for the same body weight and load. Run a within-subject design where each participant carries multiple loads to control for individual differences.

Project Variations

  • Compare youth pack designs vs. adult packs across age groups.
  • Replace MediaPipe with OpenPose and compare landmark stability.
  • Add a treadmill walk to test how dynamic loading shifts the angles.

Learn More

  • PubMed: Search backpack carriage adolescent spine reviews.
  • NIH PubMed Central: Open-access pediatric ergonomics studies.
  • MediaPipe documentation: Free pose-estimation guides.
  • American Academy of Pediatrics: Open guidelines on backpack weight.
  • MIT OpenCourseWare: Course 2.183 Biomechanics of Human Motion.
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