OpenCap

What OpenCap is

OpenCap estimates 3D human movement kinematics and forces from smartphone video for biomechanical analysis. Its outputs include joint angles, moments, and muscle forces, and example analyses cover walking, sit-to-stand, squats, drop jumps, treadmill running, and jumping. Recording uses iOS devices; users review and download their data through a web app, while videos are processed on cloud servers. Capture can use multiple cameras or a beta monocular mode with one iPhone. That single-phone mode does not require calibration.

OpenCap offers Python utilities for additional analysis, including kinetics estimation, and data can be exported as JSON, TRC, or MOT. The maker says the system has been validated against marker-based systems, and that data is encrypted in transit and at rest on HIPAA-compatible infrastructure. Its free plan is for academic or nonprofit non-commercial research or educational use. Commercial entities, including those conducting research, may not use the service and are directed to contact the authors. The development team can view submitted data, including videos, and may use it for algorithm development; investigators must obtain participant consent, and participants can choose from several public-sharing levels, including none.

Who it suits

OpenCap suits academic or nonprofit teams conducting non-commercial research or education that need movement measurements from iOS video. It can fit workflows using multiple cameras or one iPhone, with review and downloads through a web app and further analysis in Python.

Limits

The free plan is limited to academic or nonprofit non-commercial research or educational use; commercial entities, including those doing research, are prohibited from using the service. The beta monocular capture mode requires an iPhone, while multi-camera capture requires at least two iOS devices.

Getting started

1. Visit https://www.opencap.ai/ and use the free plan for academic or nonprofit non-commercial research or education.
2. For multi-camera capture, prepare at least two supported iOS devices released in 2018 or later.
3. For beta monocular capture, use one iPhone; no calibration step is needed.
4. Record movement with iOS devices, then review or download data in the web app.
5. Use the Python utilities for further analysis or export data as JSON, TRC, or MOT.

Verdict

Choose OpenCap for academic or nonprofit non-commercial movement analysis when its iOS capture and cloud workflow fit. Commercial entities should look elsewhere unless the authors authorize a route to use it; teams with video privacy constraints should also weigh development-team access.