High‐intensity exercise to improve cardiorespiratory fitness in cancer patients and survivors: a systematic review and meta‐analysis

Improving cardiorespiratory fitness (CRFit) in cancer patients is crucial to increase survivorship, promote health and improve quality of life. High‐intensity training (HIT) has the potential to increase CRFit, perhaps better than other exercise modalities, but the extant evidence has yet to be fully explored. This systematic review and meta‐analysis aimed to evaluate the effects of HIT on CRFit in cancer patients and survivors and to identify the optimal characteristics of the interventions (e.g. cancer type, intervention timing, exercise modality, intervention’s duration and the number of minutes of high‐intensity exercise in each session). The Preferred Reporting Items for Systematic Reviews and Meta‐Analyses (PRISMA) guidelines were followed. A total of 31 articles (2515 participants) were included in the systematic review and 25 in the meta‐analyses. CRFit significantly improved with HIT in comparation to a control group (p<0.00001, SMD = 0.44 and a 95% confidence interval from 0.25 to 0.64). The results obtained in the sub‐analysis were statistically significant except the comparison with the active group CRFit (p=0.13). The results showed that higher effects could be achieved in: patients starting to exercise before treatment, interventions longer than eight weeks, programs including exclusively cardiovascular training and with a high‐intensity part of session duration of at least 20 minutes.