Supramaximal High-Intensity Interval Training in People With and Without Chronic Obstructive Pulmonary Disease

COPD-HIIT is a prospective, multi-centre, randomised, controlled, parallel-group superiority trial with assessor and data analyst blinding, featuring a 1:1 allocation ratio and two separate phases. In Phase 1, the trial will investigate the effects and mechanisms of a 12 week intervention with supramaximal HIIT compared to MICT in people with COPD and matched healthy controls. Upon completing the initial 12 week intervention and follow-up assessments, people with COPD, but not healthy controls, will enter Phase 2 of the trial. Phase 2 comprises a 21 month maintenance exercise program. Subsequently, exercise training (supramaximal HIIT or MICT) will be performed until a 24 month follow-up. A separate control group of people with COPD, receiving usual care only, will undergo assessments at baseline and 24-months, making Phase 2 a partially randomized controlled trial. The primary objectives are: 1. to determine and compare the effect of 12-weeks of supramaximal HIIT and MICT on cognitive function, cardiorespiratory fitness, and muscle power in people with COPD compared to matched healthy controls (Phase 1). 2. to determine and compare the effect of 24-months of supramaximal HIIT, MICT and usual care on cognitive function, cardiorespiratory fitness and muscle power in people with COPD (Phase 2). Phase 1 and 2 of the COPD-HIIT project will be performed at two recruiting centres. 1) Department of Community Medicine and Rehabilitation, Physiotherapy, Umeå University, Umeå, Sweden and Norrlands Universitetssjukhus, and 2) Faculty of Rehabilitation Sciences, Hasselt University, Diepenbeek, Belgium and Ziekenhuis Oost-Limburg (ZOL, Genk, Belgium). In Phase 1, eligible participants will be randomized to either supramaximal HIIT (intervention arm) or MICT (active control arm) on a stationary bicycle (Smart ZBike, Zycle, Valencia, Spain). For both arms, training is performed two to three times per week for a total of 30 sessions (Table 1) using a group format with groups of 4-8 participants at the same time. Both protocols enable controlled and systematic adjustments of training intensity by means of standardized criteria to achieve a progressive overload Regarding supramaximal HIIT, importantly, while the intensity is supramaximal, it is dosed and performed at a given fraction of the maximum capacity that the person can produce during the bout (6-seconds). In contrast to an all-out regimen, or sprint interval training (SIT), this allows for the introduction and titration of intensity to the highest acceptable level without the individual feeling unwell during the process. In Phase 2, participants with COPD will enter a 21 month maintenance phase. They will continue to exercise using the same training modality (HIIT or MICT) as during the first 12-weeks but can select between three different settings to continue their training: "Home", "Outpatient", or "Mix" setting. Notably, the participant can, at any time during the maintenance period, change between the "Home", "Outpatient" or "Mix" settings when conducting their endurance training. Irrespective of the originally assigned group (supramaximal HIIT or MICT) or if the participant selects to continue in "Home", "Outpatient" or "Mix" setting, they will also perform a resistance training (RT) regime. The RT regime will consist of ten lower and upper-body exercises designed following American College of Sports Medicine guidelines and other relevant RT literature for increasing muscular strength, endurance, and power. All exercise sessions will be held and supervised by an experienced health care professional, such as physiotherapists, exercise physiologists or other health professional with equivalent expertise. All intervention providers will receive training on exercise intervention protocols to ensure standardization among centres. The between-group effects will be analyzed using analysis of covariance (ANCOVA). In the ANCOVA, baseline values, age, sex, center and VO2peak will be used as covariates. There will be one model for the COPD group and one for HC. To investigate any differential effects to the interventions between COPD and HC, an additional model including the Group (COPD/HC) × Intervention (HIIT/MICT) will be performed. Furthermore, pre-specified longitudinal mediation analyses will be performed on the entire MRI and PET/CT sample between changes in VO2peak, neurodegenerative measures, e.g., cognitive function and hippocampal volume, and inflammation levels between baseline and 24 months. Analyses will employ the intention-to-treat when applicable. Meaning that all participants randomized, whether they receive their allocated intervention or withdrew from the trial, will be included in the analysis. The primary analyses are performed using Multiple Imputation by Chained Equations (MICE) for missing data. The imputation will be done separately for each intervention arm. In addition, a per-protocol analysis (defined as \> 75% attendance rate as well as no exacerbations during the last two weeks prior to follow-up assessment), and a complete-case analysis (including participants with complete outcome measurements independent on attendance rate) will be reported. The full study protocol adheres to the SPIRIT guidelines and its outcomes extension, with intervention descriptions further guided by the TIDieR checklist the Consensus on Exercise Reporting Template (CERT). Publications from COPD-HIIT will follow the CONSORT statement, or relevant guidelines at the time of publication. Publications including qualitative outcomes will also be guided by the Consolidated Criteria for Reporting Qualitative Research (COREQ).