Fill in the blank (_) in the following sentence from the following choices.
Sentence: The man had more pain in his back than in his legs because he had been lifting with the _ .

Choice 1: The man had more pain in his back than in his legs because he had been lifting with the back .
Choice 2: The man had more pain in his back than in his legs because he had been lifting with the legs .
Which of the choices is correct? Respond with only "1" or "2" and no additional text.
1
1. The man had more pain in his back than in his legs because he had been lifting with the back.