The best replacement for hip flexion is extension.

The best alternatives to hip flexion are rated as following:
★★★★★  extension
★★  trunk flexion
★  hip extension

Your alternative for hip flexion is not listed? Suggest!
Speaking about hip flexion, one probably shouldn't forget about knee flexion.

Other search terms related to hip flexion and their ratings are:
★★★★★ knee flexion
★★★★ external rotation
You have in mind a companion for hip flexion and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of hip flexion in all years. Click on graph for more.
hip flexion
extension
trunk flexion