[peter_l_downs]

I will second the endorsement for AthleanX and KneesOverToesGuy. They have both helped me recover from injuries I suffered due to imbalances created by poor training practices. They've helped me improve both strength and mobility (turns out they're related!) and stay healthy. KOTG has been most helpful for injury recovery; Athlean X is mostly just fun. But they both promote learning about your body and the kinetic chain and how an exercise affects your muscles.

[oarfish]

If I remember correctly, AthleanX is getting a lot of heat from the science-based fitness community for unscientific advice, though I might misremember here.

However, for those interested in practical science for strength training, I would recommend Barbell Medicine's content (by actual physicians) and Stronger by Science, perhaps.

[Octabrain]

I've personally found that AthleanX has, IMO, good and informative videos but a few ones that sounded to me of looking for the controversy for the sake of views, being the one I remember the most about the "muscle-up being a showing off party trick" which is, based on my years of experience in free running, body building, gymnastics, martial arts and climbing, utterly ridiculous.

[monkeyshelli]

I also suggest checking out Squat University and Citizen Athletics.