The recruitment target was less than the target due to the reduced time available within the researchers PhD timeline (funded registration period was 1st January 2022 to 31st December 2024)

The primary aim of this randomised controlled trial is to investigate the feasibility and acceptability of low-intensity exercise with blood flow restriction (BFR) in patients with Chronic Obstructive Pulmonary disease (COPD).

The investigators will also collect functional and physiological outcome data to explore potential mechanisms and provide data for a power calculation to be used in a future randomised controlled trial (RCT) to ensure that subsequent full scale clinical RCT has maximum reach and benefit.

The primary experimental hypothesis that underpins these aims is:

• Low-intensity exercise with BFR is a tolerable, acceptable, and safe exercise modality in COPD patients.

40 patients attending clinics at University Hospitals of Leicester (UHL) National Health Service (NHS) Trust with diagnosed COPD will be randomly allocated to a home-based body weight exercise intervention either with or without the blood flow restriction (n=20 in each group). The body weight exercise will consist of five body weight exercises including: sitting knee extensions, standing knee raise, heel-toe raises, bilateral mini-squat behind a chair, and chair rise/sit to stand.

In addition to the pre and post intervention visits, the initial two training sessions for both groups will be directly supervised in the research centre. These sessions are to ensure all exercises are performed correctly and safely and the patient become familiar with the exercises and BFR equipment and mobile application, which provides exercise guidance and session recording.

Experimental design:

This is a randomised, controlled, assessor blind, single centre, clinical trial. Outcome measurements will be assessed at baseline and following the 6-week home-based intervention.

Participants:

40 Eligible participants will be identified and approached by their own clinical team at routine clinical appointments or at the point of referral to pulmonary rehabilitation (PR). In addition, potential participants who didn't attend PR or are on the waiting list and individuals who have previously provided written consent to be contacted about future research studies will be contacted via post. If interested, a researcher will explain the study and provide the Participant Information Sheet. All participants will be given at least 48 hours to consider taking part and written informed consent will be obtained before any study procedure.

Experimental protocol:

Patients will be randomised (1:1 intervention: control ratio) matched for age and lung function to a home-based body weight exercise intervention including sitting knee extensions, standing knee raise, heel-toe raises, bilateral mini-squat behind a chair, and chair rise/sit to stand either with or without the blood flow restriction (n=20 in each group).

Baseline outcome measures will be conducted over the first visits to the clinic.

Initial two training sessions will be directly supervised in the research centre (visits 2 & 3) to ensure all exercises are performed correctly and safely and the patient become familiar with the trial equipment and related mobile application for exercise guidance and session recording (digital training). During both sessions, physiological measurements will be made frequently venous blood samples to assess markers of inflammation, immune and vascular health will be obtained. A brief survey to assess exercise experience will e completed at the end of visit 3.

Patients will then be asked to carry on by performing the same exercises three times per week at home for the next five weeks. The programme will start at a quite easy level and gradually increase in intensity every two weeks depending on how the participant gets on. Progression will incorporate an increase in the number of repetitions and sets every two weeks.

After the intervention phase, patients will return to the research centre for post-intervention assessment visit (visit 4) where post-intervention outcome measures (including a post-training resting blood sample) will be conducted over the same time-course as the baseline measures. at the end of the visit, a brief survey to assess exercise experience will be completed. In addition, half of the participants will be interviewed, within four weeks of completion of the study, to qualitatively assess perceived expectations, benefits, motives, and barriers to the intervention.

Inclusion Criteria:

• Male or Female
• Aged 40 years or above
• Diagnosed with COPD as per GOLD criteria (Forced expiratory volume(FEV1)/forced vital capacity(FVC) <0.7)
• FEV1 ≤ 80% predicted
• Medical Research Council (MRC) dyspnoea scale ≥2
• BMI <= 35
• Willing and able to give informed consent for participation in the study.
• Stable dose of current regular medication for at least 4 weeks prior to study entry.
• Clinically acceptable ECG at enrolment.
• Able (in the investigators opinion) and willing to comply with all study requirements.
• Willing to allow his or her General Practitioner and consultant, if appropriate, to be notified of participation in the study.

Exclusion Criteria:

• Unable to communicate sufficiently in English
• Unable to give informed consent or comply with testing and training protocol for any reason.
• Acute exacerbation in the preceding 4 weeks (would become eligible 4 weeks following recovery).
• Unable to undertake exercise due to physical or psychological barriers.
• Contraindication to exercise training (American College of Sports Medicine guidelines)
• Any major or uncontrolled comorbidity that would impair the participant's ability to exercise or would mean exercise was unsafe (e.g., uncontrolled diabetes, hypertension BP>160/100, muscle or joint injuries which would limit ability to exercise).
• Any other significant disease, disorder, or medical condition which, in the opinion of the Investigator, may either put the participants at risk because of participation in the study, or may influence the result of the study, or the participant's ability to participate in the study including (but not limited to):

Any clotting disorder Any bleeding disorder (e.g., haemophilia) Recent (<3 months) venous thromboembolism, vascular (artery or vein) surgery to the legs, skin graft to the legs, and or arteriovenous fistula in the legs.

Had one or both legs immobilisation in the last 4 weeks (e.g., prolonged bed rest, or recent orthopaedic intervention) Taking any anticoagulant medication Significant peripheral neuropathy

• Current or within the last 3 months (or maximum relevant wash out period, whichever is longer), participation in an investigational medicinal product (IMP) or device trial at the time of screening.
• Current or within the last 6 months (or maximum relevant wash out period, whichever is longer), participation in pulmonary rehabilitation or in another research study involving exercise training.
• Scheduled elective surgery or other procedures requiring general anaesthesia during the study.
• Female participants who are pregnant, lactating, or planning pregnancy during the course of the study.

All individual patient data (IPD) that underlie results in a publication

Data requests can be submitted starting 6 months after article publication and the data will be made accessible for up to 24 months. Extensions will be considered on a case-by-case basis.

Access to trial IPD can be requested by qualified researchers engaging in independent scientific research, and will be provided following review and approval of research chief investigator and/or principal investigator.

The lead researcher performed baseline assessments prior to randomisation and was therefore blinded to group allocation. Participants were then randomised (1:1) by an independent researcher using a computer-generated sequence. Follow-up assessments were conducted by the same researcher, who was not blinded at that stage due to involvement in intervention delivery.