Using novel exercise modalities to personalise exercise training for people with chronic obstructive pulmonary disease

INTRODUCTION. Pulmonary rehabilitation (PR) is of proven benefit in the treatment of chronic obstructive pulmonary disease (COPD) leading to improvements in breathlessness, exercise capacity and quality of life. However, there remains room for improvement with some individuals not able to achieve the full benefits of PR. Several novel exercise training modalities, such as eccentric cycling, are now available, providing an opportunity to further personalise the delivery of PR. This thesis explores the impact of disease characteristics on physiological improvements following exercise training in COPD and investigates how novel exercise training modalities can be used to personalise PR.

METHODS. This thesis comprises:

1) A systematic review and meta-analysis to investigate whether V̇O2peak improves following exercise training in COPD and determine which patient and programme factors influence this response;

2) Two laboratory studies to examine the physiological response to eccentric cycling in individuals with COPD and younger and older healthy adults;

3) A pilot randomised controlled trial to investigate how mechanisms of exercise limitation impact on performance and training progression for novel and traditional exercise modalities.

RESULTS. Exercise training in COPD induces moderate improvements in V̇O2peak (SMD 0.52;95%CI 0.34-0.69) but the response is variable and cohorts with more severe airflow obstruction demonstrated smaller improvements in V̇O2peak (p<0.001). The change in V̇O2peak was positively associated with target duration of exercise bout (p=0.01) and, when studies over one year duration were excluded, greater total volume of exercise training (p=0.01). However, reported prescribed exercise intensity (p=0.77), training modality (p>0.35) and mode (p=0.29) did not affect V̇O2peak.

Eccentric cycling results in lower oxygen uptake, minute ventilation, heart rate, systolic blood pressure, RER (p<0.001), capillary lactate, perceived breathlessness and leg fatigue (p<0.05) than concentric cycling at matched mechanical load in COPD and healthy controls. Increases in muscle lactate content (p=0.008) and decreases in muscle phosphocreatine (p=0.012) seen during concentric in COPD, were not evident during ECC.

Individuals with a ventilatory limitation to maximal exercise (peak VE>85% predicted MVV) may achieve greater relative training loads during novel exercise modalities than those without a ventilatory limitation. Psychological distress, fatigue and breathlessness were highest and positive wellbeing (PWB) lowest during concentric cycling as compared to eccentric cycling, one-legged cycling and resistance training.

CONCLUSION. Overall, people with COPD achieved moderate improvements in V̇O2peak through supervised aerobic training. There is sufficient evidence to show that programmes with greater total exercise volume, including duration of exercise bout and programme duration, are more effective. Reduced effects in severe disease suggest alternative aerobic training methods may be needed in this population. Novel exercise modalities such as eccentric cycling and one-legged cycling have the potential to target these individuals and it appears that those with a ventilatory limitation are the group most likely to benefit from novel exercise modalities. Eccentric cycling results in low cardiometabolic demand for individuals with COPD allowing improved comfort and higher mechanical loads but may not stimulate metabolic adaptation.