Truthfully when a person starts PE He needs to develop a new frame of reference.
By that I mean this,we are so conditioned to having things happen in an instant.
Instant rice,popcorn whatever.Everything is geared to instant gratification
Than you have these adds promising "Get 3 inches in three weeks".
PE is not like that.It is a process.It takes time and effort.
Sure some gain faster than others but it still takes time.
The rewards of our labor come in increments,not instant inches.
But they all add up over time
The problem is, that someone new to PE sees someone routine or advanced exercise
their doing and start doing something they are not conditioned for.
A warning sign should come on"Injury ahead if you proceed'
But They proceed with much gusto,and wonder why they got got injured
PE should be a healthy habit, not an injurious assault.