How does running form analysis work?
Running form analysis works by finding your joints in every frame of a short video, measuring the angles between them at foot strike, midstance and toe-off, and comparing those angles to ranges a coach would call good, fair or worth fixing.
Step 1: find the joints
Software called a pose estimator looks at each frame and marks key points: ankles, knees, hips, shoulders, elbows, wrists, ears. It has learned what a human body looks like from millions of images, so it can do this on a normal phone video at 30 frames per second. The model can run on the phone or on a server. Caden runs it on a server, so the clip uploads first.
The output is a stick figure, a skeleton, drawn over you in every frame.
Step 2: find the moments that matter
A stride has three moments coaches care about:
- Foot strike. The first frame where the front foot touches the ground.
- Midstance. The frame where the hip passes directly over the planted foot.
- Toe-off. The last frame before the back foot leaves the ground.
The software finds these by watching the ankle's height and speed. It picks the frames automatically so every clip is measured at the same points, which is what makes results comparable month to month.
Step 3: measure the angles
At each moment, it measures a small set of things:
- how far ahead of the hip the ankle lands, as a fraction of leg length,
- how bent the front knee is,
- how far the torso leans from vertical,
- how bent the trailing knee is during recovery,
- the elbow angle,
- how far the head sits forward of the trunk line,
- and cadence, from counting foot strikes over the clip.
These are 2D angles in the camera's plane. A side view sees lean and reach. A front view sees hip and shoulder tilt. Neither sees force.
Step 4: score and explain
Each measurement is compared with a range. Land under the hip with a soft knee and you score high. Land far ahead with a straight leg and you score low. A form score out of 100 summarises the set.
The good tools then do the part most skip: they turn the low score into a cue and a plan. See how to get feedback without a coach.
What it cannot do
It cannot measure ground reaction force, pronation, or rotation you cannot see from the camera. It cannot diagnose why something hurts. And it is only as good as the clip. A dark, distant or shaky video gives noisy joints and noisy numbers. See how accurate are running form apps.
How to check it with Caden
- Tap Run a new analysis.
- Film 10 to 20 seconds from the side at easy pace with the phone at hip height.
- The clip uploads with the audio removed. Caden's servers run pose estimation, find foot strike, midstance and toe-off, and return the six dials and cadence.
- Tap Breakpoints and toggle Skeleton to see the joints it found on each frame. If they sit on your actual joints, trust the numbers.
FAQ
Does running form analysis need special sensors?
No. Video-based analysis needs only a phone camera. Sensor-based systems use insoles or a pod on your shoe and measure different things, such as ground contact time.
Is the analysis done on my phone or in the cloud?
It depends on the app. Caden uploads the clip with the audio removed and runs pose estimation on its servers, storing the media privately under your account until you delete the analysis. Some competitors work the same way. A few run everything on the device.
How long does a running form analysis take?
Filming takes seconds. Upload plus analysis usually takes about a minute, depending on the clip and your connection.