Can overexertion generally leads to ligament and tendon damage.

Yes it is true, i actually know from experience.

Maybe it is yoga , stretches, push ups, sit up etc

It doesn't state that he washed his hands before or after preparing this poultry. even though he had it in seperate bags the bacteria from the poultry could have entered the vegtables because of a lack of handwashing. so cross-contamination is a very possible answer.