The crunch factor's role in golf-related low back pain

Background context: The golf swing exposes the spine to complex torsional, compressive, and shearing loads that increase a player's risk of injury. The crunch factor (CF) has been described as a measure to evaluate the risk of low back injuries in golfers and is based on the notion that lateral flexion and axial trunk rotation jointly contribute to spinal degeneration. However, few studies have evaluated the appropriateness of this measure in golfers with low back pain (LBP).

Purpose: To objectively examine the usefulness of the CF as a measure for assessing the risk of low back injury in golfers.

Study design: Field-based research using a cross-sectional design.

Methods: This research used three-dimensional motion analysis to assess the golf swings of 12 golfers with LBP and 15 asymptomatic controls. Three-dimensional kinematics were derived using Vicon Motus, and the CF was calculated as the instantaneous product of axial trunk rotation velocity and lateral trunk flexion angle.

Results: Maximum CFs and their timings were not significantly different between the symptomatic and asymptomatic groups. Furthermore, for those golfers who produced higher CFs (irrespective of the group), the increased magnitude could not be attributed to an increased axial angular trunk velocity or lateral flexion angle, but rather to a concomitant increase in both of these variables.

Conclusions: The findings suggested that although the fundamental concepts that underpin the CF seem sensible, this measure does not appear to be sensitive enough to distinguish golfers with LBP from the asymptomatic players.