RecruitingBehavioural interventionTai Chi for Reducing Aromatase Inhibitor-Induced ArthralgiaThe objective of the pilot RCT is to evaluate the feasibility and acceptability of a Tai Chi intervention "TaiChi4Joint" vs. an HE AC group for relieving AIIA in women with hormone receptor positive stage I-III BCa. The investigators will pilot test our data collection for mechanism measures via three innovatively integrated biobehavioral pathways.