Question: what is the origin of the primary muscle used in a chin up
[{'answer': 'biceps', 'provenance': [{'wikipedia_id': '2608717', 'title': 'Chin-up', 'start_paragraph_id': 1, 'start_character': 190, 'end_paragraph_id': 1, 'end_character': 196, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]