Question: what form of exercise does the muscle contract and does not lengthen nor shorten
[{'answer': 'isometric', 'provenance': [{'wikipedia_id': '1110611', 'title': 'Muscle contraction', 'start_paragraph_id': 2, 'start_character': 118, 'end_paragraph_id': 2, 'end_character': 127, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '1110611', 'title': 'Muscle contraction', 'start_paragraph_id': 8, 'start_character': 0, 'end_paragraph_id': 8, 'end_character': 275, 'bleu_score': 0.957870874785216, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 8348122433272126572}, 'section': 'Section::::Types.:Isometric contraction.\n'}]}]