Exploring Resistance Exercise Training Plus High-Intensity Interval Training (ReHIIT) as Cancer Prehabilitation

Colorectal cancers are a leading cause of death in the UK, but many can be cured with surgery alone. From diagnosis to surgery or alternative first treatment, the UK government mandates a maximum timeline of 31 days, providing only a short window in which patients may be physically optimised by exercise before surgery. There is increasing interest in clinical and academic settings regarding the potential benefits of exercise-based surgical prehabilitation. Although surgery is often successful, the combined effects of cancer and surgical stress can lead to poor clinical and patient-centred outcomes, including delayed return to normal activities and reduced quality of life. Physiological parameters known to be improved through exercise training, such as cardiorespiratory fitness and muscle mass, have been associated with more favourable clinical outcomes for individuals undergoing colorectal cancer surgery, including anaesthetic risk and tolerance to adjuvant treatment. The limited time available before surgery remains a major challenge. Traditional modes of exercise training, including aerobic and resistance exercise performed separately, typically require six weeks or more to produce meaningful improvements in their primary physiological adaptations. As a result, recent cancer rehabilitation research has increasingly used high-intensity interval training (HIIT) because it requires less time and has been shown to improve both cardiorespiratory fitness and muscle mass more rapidly than traditional exercise modalities. Although HIIT has demonstrated potential in several patient groups, previous work has shown that individuals with colorectal cancer may not experience improvements in cardiorespiratory fitness or muscle mass after a four-week HIIT intervention, even though the same protocol has produced adaptations in older adults and individuals with other cancer types. This may reflect a degree of anabolic or physiological resistance in the colorectal cancer population. Based on this, a current trial is comparing HIIT alone with a combined approach of HIIT plus resistance exercise training (ReHIIT) to determine whether the addition of resistance exercise can overcome this reduced adaptive response. However, the expected magnitude of physiological adaptation to four weeks of ReHIIT in adults without cancer has not been fully characterised. This study will therefore explore changes in cardiorespiratory fitness, muscle mass, and associated metabolic and molecular mechanisms in healthy adults following a four-week ReHIIT programme.