Background: Online behaviour change interventions (OBCI) to improve physical activity (PA) have not yet been properly explored in adults with asthma.

Aims: To verify the effectiveness of an OBCI in improving PA and clinical outcomes and reducing sedentary behaviour (SB) in adults with asthma.

Methods: The PA and SB levels of adults with stable asthma were evaluated through accelerometry. They filled in the Basic Psychological Needs in Exercise Scale (BPNES) and the Asthma Control Questionnaire (ACQ) and performed an incremental step test (IST). After randomization, both groups (control [CG] and intervention [IG]) received an educational program, and the IG also received an OBCI for 12 weeks.

Results: 43 participants (IG=23, CG=20, 41±11 years, 31±6 Kg/m², FEV₁ 77±20%predicted) were analysed. There was no significant change in PA or SB when comparing the groups (P?0.28). However, participants from IG felt more competent (post-pre [?]: 5.6±4.4 vs. 1.3±6.8 pts; P=0.003) and autonomous (?: 5.6±5.2 vs. 0.7±4.7 pts; P=0.02) to exercise than participants in CG. In addition, participants in the IG had greater improvement in the ACQ score (?: -0.6±0.8 vs. -0.1±0.9; P=0.09) and IST (?: 35±52 vs. 5±45 steps; P=0.06) compared to CG. Further, 61% of IG and 35% of CG reached the minimal clinically important difference for the ACQ (P=0.09).

Conclusions: These preliminary data show that this OBCI had no marked additional value to the educational program in improving PA and reducing SB. However, it supported basic psychological needs to exercise and improve asthma control and exercise capacity. Basic needs support drives lasting behaviour change.