AxyZ uses computer vision to extract biomechanical measurements from a short side-view video of you riding. This page explains exactly what the AI measures, how it works, and what the results mean for your fit.
AxyZ analyzes video using MediaPipe Pose, a computer vision model developed by Google Research that detects 33 body landmarks in real time. The model tracks the position of your joints — including the hip, knee, ankle, shoulder, and elbow — in every frame of your video.
For a 10-second clip at 30 frames per second, AxyZ processes approximately 300 frames. It identifies the frames that correspond to the top and bottom of the pedal stroke (top dead center and bottom dead center) and extracts angle measurements at each of those positions across multiple pedal cycles. This multi-cycle averaging reduces the impact of frame noise and gives a more reliable measurement than any single snapshot.
MediaPipe Pose is the same computer vision foundation used in professional sports analysis applications, physical therapy tools, and motion capture research. AxyZ applies it specifically to cycling biomechanics using established bike fitting benchmarks as the reference standard for each metric.
Saddle height is the most impactful variable in bike fitting. AxyZ measures the angle at your knee joint when the pedaling crank is at the bottom of its rotation (bottom dead center, or BDC). The established benchmark for most cyclists is 25–35 degrees of knee flexion at BDC.
A saddle set too low produces a knee angle below 25 degrees — excessive flexion that loads the patella and causes anterior knee pain. A saddle set too high produces an angle above 35 degrees — insufficient flexion that forces the hip to rock laterally on each downstroke, straining the IT band and reducing power transfer. AxyZ accounts for your crank length (which you enter before upload) when calculating the target range, since longer cranks require slightly different saddle positions for the same knee angle.
Hip angle is measured at the top of the pedal stroke (top dead center, or TDC), where the hip is at maximum flexion. The target range for most cycling disciplines is 45–60 degrees of hip angle at TDC — enough to generate force through the top of the stroke without compressing the hip flexors or rotating the pelvis.
A hip angle below 45 degrees (too closed) indicates the saddle may be too high or the handlebar stack too low, causing hip impingement on the upstroke. An angle above 60 degrees (too open) suggests the rider is sitting too upright relative to the crank — common when the saddle is too low or the cockpit is set too high for the rider's goals. This metric is particularly relevant for triathletes and time-trial riders, where aerodynamic position must be balanced against hip clearance.
Torso lean measures the angle of the rider's upper body relative to vertical. Unlike saddle height, there is no universal target for torso angle — the ideal position depends on the rider's discipline, flexibility, and comfort goals. Road cyclists targeting aerodynamics typically aim for 40–45 degrees of torso lean; recreational and fitness riders are typically comfortable at 55–70 degrees; mountain bikers vary significantly by terrain.
AxyZ scores torso lean against a range appropriate for the bike type you select during upload. It also notes whether shoulder position is symmetrical and whether the rider's weight appears to be over-loaded onto the hands — a sign of excessive reach or insufficient core engagement.
Pedaling stability measures how much the pelvis moves laterally during the pedal stroke. A well-fitted rider maintains a relatively stable pelvis; rocking from side to side indicates that the rider is compensating for a position that does not match their anatomy. The most common cause is a saddle that is too high — the hip drops on each downstroke as the rider reaches for the pedal.
AxyZ tracks hip landmark height across multiple pedal cycles and calculates the standard deviation of lateral displacement. Scores are relative: less than 10mm of average lateral movement is considered stable; above 20mm flags a significant rocking pattern worth addressing.
AxyZ's accuracy depends primarily on camera placement and video quality. Follow these guidelines for the most reliable measurements:
AxyZ is a directional tool. It identifies which fit variables are likely outside your optimal range and ranks the adjustments that will have the highest impact on your comfort and efficiency. It is not a replacement for a professional in-person bike fitting, which uses 3D motion capture, pressure mapping, flexibility assessment, and physical examination over 1–3 hours.
The primary limitation of 2D video analysis is that it captures only one plane of motion. Lateral knee tracking, cleat alignment, and fore-aft saddle position are difficult to assess reliably from a side-only view. AxyZ focuses on the four metrics where side-view 2D analysis produces reliable, actionable data — saddle height, hip angle, torso lean, and pelvic stability — and avoids reporting on variables where the measurement would be unreliable.
Crank length affects the geometry of the pedal stroke. AxyZ asks for your crank length during upload and uses it to adjust the target angle ranges for saddle height and hip angle. Cranks typically range from 165mm (shorter riders, more hip-clearance-focused) to 175mm (taller riders, traditional road geometry). Using the wrong crank length in the upload form will shift your scores, so measure the number printed on your crank arm before submitting.
After processing your video, AxyZ returns a scored report covering all four metrics. Each metric receives a numerical score and a status (optimal, minor adjustment needed, or significant adjustment needed). The report also includes:
Pro users can save analyses to their fit history and compare results across sessions — useful for tracking the effect of saddle changes, weight shifts, or new bike setups over time.