To improve your squat depth, prioritize active mobility work (such as holding the bottom position of a squat with a light counterweight) rather than passive stretching, as the body requires strength and control to fully utilize its range of motion.

noli's read

The distinction between passive flexibility and active mobility is widely validated by sports science. A systematic review by O'Sullivan et al. (2012) demonstrates that strengthening through full ranges of motion (such as the loaded squat) actively improves overall flexibility, often proving more effective than static stretching. Conversely, a meta-analysis by Kay and Blazevich (2012) confirms that isolated passive stretching has very little transfer to dynamic performance and motor coordination. Biomechanically, using a front load (the goblet squat) acts as a natural counterweight that shifts the center of gravity forward, which facilitates deeper hip flexion without loss of balance (consensus of biomechanics experts). While the dramatic improvement after only "5 repetitions of 20 seconds" is more likely a temporary decrease in the nervous system's protective reflex (stretch tolerance) rather than a physical change in muscle length, it nonetheless serves as an excellent learning tool for reprogramming movement.

the sources

1. 1Weppler CH, Magnusson SP 2010
2. 2Behm DG, Blazevich AJ, Kay AD, McHugh M 2015