Question: muscle fatigue occurs due to a buildup of
[{'answer': 'metabolites', 'provenance': [{'wikipedia_id': '841074', 'title': 'Muscle fatigue', 'start_paragraph_id': 16, 'start_character': 238, 'end_paragraph_id': 16, 'end_character': 249, 'bleu_score': 1.0, 'section': 'Section::::Metabolic fatigue.:Metabolites.\n'}]}, {'provenance': [{'wikipedia_id': '841074', 'title': 'Muscle fatigue', 'start_paragraph_id': 16, 'start_character': 0, 'end_paragraph_id': 16, 'end_character': 494, 'bleu_score': 0.970362113628587, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6097752170961804835}, 'section': 'Section::::Metabolic fatigue.:Metabolites.\n'}]}]