Sentence 1: I was in the gym. 
 Sentence 3: My trainer insisted that I don't lock out my knee in the leg press 
 Sentence 4:  I decided not to listen to his advice 
 Sentence 5:  I locked out my knee and it snapped in half under the pressure 
 Option 1: I decided to use the leg press machine. 
 Option 2: I decided to use the bicep curl machine.