Actually I have, for the past 8 years, done very intensive study on biomechanics and exercise physiology. The average Joe knows probably nothing about proper exercise and most thing professionals are taught nowadays is plain wrong.
There are off course exceptions to this situation but damned few. All physiotherapist and trainers I’ve ever talked to are still under the impression that one should train more and more as one get stronger. The opposite is true off course. None of them had the slightest idea about body leverage factors, neuromuscular efficiency, fibre type specific training or even basic functions of most muscular structure in the body.
I've seen professional trainer’s advice their underage trainees to do jump squats, explosive leg presses, lunges etc. See their trainees do squats an deadlifts with clearly bend backs, rueing their back in the progress, with their trainers looking at it in total ignorance.
I'm a mechanical engineer so I know a thing or two about mechanics and the basic science behind it. Without this knowledge it is simply impossible to understand biomechanics. The mechanics and physical laws are universal and apply to all things, human body’s are no exception to any of those laws.
Most physical therapist (and trainers) don't even understand, nor are aware of, the most basic physical principles things like friction, moment arm factors, momentum, impact forces, potential energy, kinetic energy, heat production etc. Without this knowledge it is impossible to understand the body let alone exercise.