You probably just have bad mobility/dynamic flexibility and a poor range of motion.

I remember some of these excercises were hard for me back in the day to (especially the 4 star drill) there tiring as hell for the legs

Btw dont know whether you know this but plyometrics are best performed like in the afternoon/night.

Try find a foam roller and tennis ball and massage the area that hurts or get some heat cream. I currently have a muscle strain in my hip flexor from my fall and yeh i agree it a bitch.

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