<jats:title>Abstract</jats:title><jats:sec> <jats:title>Background</jats:title> <jats:p>Early mobilisation (&gt; 24 h post-stroke) is recommended for people with stroke. However, there is a paucity of evidence about how to implement early mobilisation for people who have had a severe stroke. Prolonged standing and task-specific training (sit-to-stand repetitions) have separately been evaluated in the literature; however, these functionally linked tasks have not been evaluated in combination for people with severe sub-acute stroke.</jats:p> </jats:sec><jats:sec> <jats:title>Methods</jats:title> <jats:p>The objective was to determine the feasibility of conducting a randomised controlled trial (RCT) of a functional standing frame programme compared with usual physiotherapy for people with severe sub-acute stroke. An assessor-blinded feasibility RCT with nested qualitative component (interviews and focus group) and process evaluation was adopted. Participants were aged ≥ 18 years with new diagnosis of severe sub-acute stroke (modified Rankin Scale (mRS) 4/5) from four Stroke Rehabilitation Units across South West England. Participants were randomised to receive either: (1) functional standing frame programme (30 min. standing plus sit-to-stand repetitions) plus 15 min of usual physiotherapy daily (intervention); (2) usual physiotherapy (45 min) daily (control). Both programmes were protocolised to be undertaken a minimum of five sessions per week for 3 weeks.</jats:p> <jats:p>Feasibility indicators included process, resource, management, and safety. Adherence, fidelity, and acceptability of the trial and intervention were evaluated using data recorded by therapists, observation of intervention and control sessions, interviews and one focus group. Patient measures of motor impairment, activities/participation, and quality of life were carried out by blinded assessors at baseline, 3, 15, 29, and 55 weeks post-randomisation.</jats:p> </jats:sec><jats:sec> <jats:title>Results</jats:title> <jats:p>Forty-five participants (51–96 years; 42% male, mRS 4 = 80% 5 = 20%) were randomised (<jats:italic>n</jats:italic> = 22 to intervention). Twenty-seven (60%) participants were followed-up at all time points. Twelve participants (27%) died during the trial; no deaths were related to the trial. Adherence to the minimum number of sessions was low: none of the participants completed all 21 sessions, and only 8 participants (18%) across both groups completed ≥ 15 sessions, over the 3 weeks; 39% intervention; 51% control sessions were completed; mean session duration 39 min (SD 19) control, 37 min intervention (SD 11). Intervention group: mean standing time 13 min (SD 9); mean sit-to-stand repetitions/session 5 (SD 4).</jats:p> <jats:p>Interviews were conducted with 10 participants, four relatives and six physiotherapists. Five physiotherapists attended a focus group.</jats:p> </jats:sec><jats:sec> <jats:title>Conclusions</jats:title> <jats:p>The majority of progression criteria for this feasibility trial were met. However, adherence to the interventions was unacceptably low. This aspect of the trial design needs to be addressed prior to moving to a definitive RCT of this standing frame intervention in people with severe sub-acute stroke. Solutions have been identified to address these concerns.</jats:p> </jats:sec><jats:sec> <jats:title>Trial registration</jats:title> <jats:p>International Standard Randomised Controlled Trial Number <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://www.isrctn.com/ISRCTN15412695">ISRCTN15412695</jats:ext-link>. Registration 19 December 2016.</jats:p> </jats:sec>