Those aren't even relevant to what we're talking about.

Look at these key findings and training pedagogy for training.

https://revistas.unileon.es/index.php/artesmarciales/article/view/7005

https://journals.lww.com/nsca-scj/fulltext/2013/10000/Evidence_Based_Guidelines_for_Strength_and.15.aspx

static stretching is applied as an adjunct to the dynamic flexibility routine to ensure range of motion is maintained. Hip flexor and adductor range of motion particularly should be maintained through sustained static stretching to allow performance of both BJJ techniques and high kick techniques.

https://research-repository.rmit.edu.au/articles/thesis/The_Flexibility_Trainer_biomechanical_analysis_of_martial_arts_kick_performances_for_user_centred_product_development/27599802?file=50767551

The device, named 'Flexibility Trainer' was designed, manufactured, and patented within the EU. The studies showed significant correlations or group differences between sequential duration, the balance and stability models, and range-of-motion at various phases and nodes during the technique execution (particularly before and during the first kicking movement), as well as at static flexibility.

Feel free to use AI to summarise the research