BACKGROUND: Patients with COPD and patients with bronchiectasis undertake airway clearance therapy and exercise as part of management, but the effect of these activities on gastroesophageal acid exposure is unknown. This study aimed to determine if positive expiratory pressure (PEP) therapy and standardized exercise tasks were associated with increased gastroesophageal reflux. METHODS: During dual-probe 24 hour esophageal pH monitoring, all participants undertook a single session of PEP therapy, a measure of submaximal exercise capacity (6-min walk test [6MWT]), and a functional upper limb task (grocery shelving task [GST]). The number of reflux episodes and fractional reflux time (reflux index [RI]) were recorded during each intervention and compared to equivalent background time (BGT). RESULTS: Fifty-seven participants (30 with bronchiectasis, 27 with COPD, mean ± SD age 61 ± 13 y, FEV(1) 61.2 ± 24.6% predicted) completed the study. Episodes of isolated distal esophageal reflux occurred in 30% of participants during PEP therapy, 22% during the 6MWT, and 20% during the GST. However, there was no significant difference in distal RI during 6MWT or PEP therapy, compared to BGT (all P > .05). The number of reflux episodes was decreased, compared to BGT during the GST (P = .001) and 6MWT (P = .001), but not during PEP therapy (P = .71). CONCLUSIONS: Episodes of gastroesophageal reflux may occur during physiotherapy tasks, including airway clearance therapy using mouthpiece PEP, the 6MWT, and a measure of upper limb movement. However, as these activities did not increase the frequency of these events, no modifications to these tasks to minimize the occurrence of gastroesophageal reflux are necessary.