Digital interventions can increase physical activity (PA) levels in adults. However, the COVID-19 pandemic highlighted the complexities faced when guiding people to start or return to PA following illness or inactivity. A digital tool, Movement Foundations, was developed to provide remote guidance on building strength and capacity across functional movement patterns, with graduated progression based on user responses and input. This qualitative study aimed to explore the perceived impacts of using the tool. Nine participants aged over 35 years from the healthcare and academic healthcare sectors were recruited to use it and were subsequently interviewed. Thematic analysis identified three themes falling under the overarching concept of ‘Capability, Opportunity and Motivation—Behaviour (COM-B) Plus’, encompassing: skills and capacity for movement; opportunities, motivations and barriers for movement; and a personalised, safe space in which to develop. Participants felt that the digital tool increased their capacity and confidence in movement and positively impacted their daily activities. External factors such as illness and stress clouded perceptions of the impacts of PA. Time, work pressures and needing equipment were still considered significant barriers to PA. Still, participants appreciated the flexibility and non-prescriptive nature of the tool and felt that it helped movement to become opportunistic and habitual. Increased capacity for PA and feeling the subsequent physical and mental effects positively influenced motivation. Structure and guidance, with graduated progress, were seen as protective. Guided self-reflection helped participants understand their capacity and limitations with regard to movement and promoted motivation. Although acquiring technical skills to guide movement may be important for those recovering from illness, participants found that a structure promoting individualised guidance, graduated progression and guided self-reflection were important motivational factors for continuing use. Digital interventions should consider these aspects when seeking to promote habitual PA.