Darell has a home gym that his older brother set up. nobody has used the gym for a few years but darell has decided to give weight lifting a try. he talks to his gym teacher, who shows him proper form for the exercises and does performance testing. together they design a starter program that includes a warm-up, stretching, and some basic weight-lifting exercises, followed by a time of stretching. on the first day of his routine, darell is injured. what is the most likely cause of his injury?