Alternative Models for Pelvic Marker Occlusion in Cycling.

Area of Science:

• Biomechanics
• Sports Science
• Ergonomics

Background:

• Accurate joint center identification is crucial for bike fitting to enhance performance and prevent injuries.
• Locating the hip joint center is challenging in cycling due to marker occlusion, particularly the anterior superior iliac spine markers.

Purpose of the Study:

• To validate a modified pelvic model (MPM) for hip joint center calculation in cycling, addressing marker occlusion issues.
• To compare the MPM with the traditional pelvic model (TPM) and the widely used trochanter model (TM).

Main Methods:

• Thirty-one recreational cyclists were analyzed using a 7-camera VICON motion capture system on a roller bike.
• The hip joint center and knee angle were calculated using the MPM, TPM, and TM.
• Comparisons were made continuously and at specific crank positions (90° and 180°).

Main Results:

• No significant differences were found between the MPM and TPM for hip joint center position or knee angle.
• Significant differences were observed between the TPM and TM, with variations of 4.1° to 6.9°.
• Bland-Altman analysis showed minimal bias between MPM and TPM, but notable differences between TPM and TM.

Conclusions:

• The modified pelvic model (MPM) is a valid and reliable tool for bike fitting, effectively overcoming marker occlusion problems.
• The MPM provides accurate hip joint center estimations comparable to the traditional pelvic model (TPM).
• The trochanter model (TM) may introduce measurement errors, questioning its utility in diagnostic bike fitting.