Trunk Angle
Target≈40°–45° above horizontal for road endurance (lower = more aggressive/aero)
angle of the trunk line (hip → shoulder) versus horizontal, on a steady seated frame.
Why this matters
Trunk angle is the headline posture variable: it trades aerodynamics against comfort and breathing. Because the upper body stays still while the legs cycle, it's a held reading — take it on any steady seated frame.
What good looks like
A long, supported torso at ≈40°–45° for endurance road riding: low enough to be efficient, high enough to sustain for hours without low-back or neck strain.
Common faults
- Too aggressive for the rider's mobility — low angle but rounded lumbar spine and craning neck.
- Too upright — comfortable but costs noticeable aerodynamic drag.
Coaching cues
- Lower the bars gradually and only as hip/hamstring mobility allows.
- Check the rider can hold the posture without the low back rounding.
How to draw
- Pick a steady seated frame at a consistent crank position.
- Draw greater trochanter (hip) → acromion (shoulder).
- Read the angle versus horizontal.
Related measurements
- Hip Angle at TDC — a low trunk angle closes the hip more at the top.
- Elbow Angle — reach interacts with how the trunk is supported.
General bike-fit guidance, not a clinical recommendation. Strongly bike-type dependent (a TT/aero position is far lower).
source · sports/cycling/learn/cycling_trunk_angle.md