Say a man is twisting his body using internal body muscle contractions and torque interactions between his feet and ground (no slipping).
From the answers of a previous question I raised, these ground reaction forces/torques will not do any work on the man (and also no work done to the ground by him) but yet he is increasing his angular momentum and rotational kinetic energy. Can I therefore assume this means he is just transforming other forms of internal body energy to increase his rotational kinetic energy (especially if no work is done on him via the ground)?
So is the real reason why his angular momentum is not conserved due to a change from one form of internal energy to rotational kinetic energy? If yes, would it be incorrect to state that the reason the man’s angular momentum is not conserved is because of an external torque applied to him (ie. the system) from the ground?