Background
Among all cancers, the diagnosis of prostate cancer is associated with the greatest number of years lived with the disability and side effects of cancer. The treatment of men with prostate cancer can have a significant adverse effect on physical health. One of the primary treatment modalities is androgen-deprivation therapy which can be associated with reduced muscle mass, strength, fatigue, insulin-resistance, higher rates of cardiovascular morbidity and reduced bone density. Exercise is an increasingly prescribed solution and it has been shown that cardiorespiratory fitness and physical activity have an important survival role but one that is often under-utilised. In terms of mortality, cardiovascular disease is the leading cause of death in patients with prostate cancer and exercise to increase physical activity is recommended in the American College of Sports Medicine's (ACSM) guidelines to counter this, given the clear cardioprotective effects it has.
The World Health Organisation defines the term "physical activity" as "any bodily movement produced by skeletal muscles that requires energy expenditure" and differentiates it from "exercise" which it defines as "a subcategory of physical activity that is planned, structured, repetitive, and purposeful" in order to improve or maintain physical fitness. There is good evidence from a systematic review and meta-analysis that exercise in patients with prostate cancer is safe, improves aerobic fitness and muscular strength, fatigue, body mass composition, quality of life and physical function.
There is no consensus over the detail of exercise prescription in cancer survivors and there are considerable differences between the protocols in studies to date. Many studies have employed moderate intensity activities such as cycling, jogging, walking or using a cross trainer but the frequency and duration employed have not been consistent, ranging from 2 to 7 days a week and 15-60 minutes per session.
Other than duration and frequency, one other important variable in exercise interventions is exercise intensity. The ACSM guidance highlights this as an area where knowledge is lacking and thus where further research is needed. In terms of physical activity in healthy populations, there is believed to be a dose-response relationship of volume with all-cause mortality, however, higher intensity might be able to produce similar results to increasing volume.
High intensity exercise is considered to be when a person exercises at greater than or equal to 80% of their maximal oxygen uptake capacity (VO2 MAX). In patients with cancer, intensity is the strongest component of an exercise regime that predicts improvements in quality of life. Higher intensity exercise can also lead to improvements in fatigue, aerobic fitness, muscle strength and function as well as an inverse link with the risk of premature death in cancer survivors.
The first interventions examining high intensity training in patients with prostate cancer employed sessions of 35 minutes with varying intervals from 1 - 25 minutes. These studies reported improvements in physiological function, such as reductions in fasting glucose and increases in the cardioprotective high-density lipoprotein. Subsequent studies have reproduced the physiological gains from high-intensity training and found them to be superior when compared to lower-intensity training. Even short interventions in cancer patients, such as 6 weeks, appear to provide significant improvements in VO2MAX.
Time and enjoyment are often cited barriers to regular physical activity and thus, high intensity interval training (HIIT) has been offered as a potential time-efficient solution that is perceived as more enjoyable than moderate continuous training in both healthy and cancer patients. HIIT can take a number of forms but a commonly employed protocol consists of 4-10 repeated maximal Wingate sprints with rest intervals in between. The total duration of the sessions, including the warm-up and warm-down, however, lasted a similar duration to the continuous moderate exertion aerobic exercise protocols. The protocol has, therefore, now been further condensed to reduced-exertion HIIT sessions (REHIT). This consists of 10 minutes of low intensity workload incorporating two or three 20 s Wingate sprints at set intervals. It was hypothesised by Metcalfe et al that, because energy stored in the muscle as glycogen was depleted to a similar extent in shorter 15-20 second sprints compared to the traditional 4-6 x 30 second sprints in HIIT, the shorter sprints would still produce physiological improvements. Indeed, REHIT improved both VO2MAX and insulin sensitivity.
Evidence that HIIT results in greater physiological benefits and for less time commitment than those achieved by continuous moderate intensity training in healthy populations is now well established and growing evidence replicates these findings in patients with cancer. REHIT could therefore provide patients with prostate cancer an opportunity to achieve at least the same physiological benefits as continuous moderate intensity training but with much less time commitment. The aim of this project is to investigate whether a REHIT intervention results in improved cardiorespiratory fitness in patients with prostate cancer.
Participants
For this pilot study, 30 patients who have been diagnosed with prostate cancer will be recruited from a number of Gloucestershire-based sites; a Macmillan Cancer Support initiative called Next Steps, a patient-let prostate cancer support group and the Gloucestershire Hospitals NHS Foundation Trust's uro-oncology specialist nurse service. Participants will be asked to give their written consent to participate in the study. Patients with activity status of "high", as assessed using the International Physical Activity Questionnaire (IPAQ), will be excluded from the study. The period of recruitment will be November 2017 to February 2019. Participants will be randomised to a control group or the exercise intervention group. The study will be subject to gaining ethical approval from the University of Bath Research Ethics Approval Committee and the NHS Research Ethics Committee.
Baseline Testing
The pre- and post-intervention cardiorespiratory fitness testing will be conducted at the University of Gloucestershire's Performance Laboratory. Pre-intervention maximal oxygen uptake capacity testing (VO2 max), will be performed at the initial visit to the laboratory. This will be determined using an incremental cycling test to volitional exhaustion on a cycle ergometer and a metabolic cart to analyse VO2 MAX. Patients will be asked to perform a 2-minute warm-up at 50 watts before an incremental 1 watt per 3 seconds to volitional exhaustion with verbal encouragement. VO2 MAX will be taken as the highest value in a 15-breath rolling average.
Experimental Procedures
Following baseline testing, participants in the exercise group will start a 6-week training protocol involving 3 sessions a week. The REHIT interventions will utilise a gym in Gloucestershire used by the Macmillan Cancer Support's Next Steps project. Each session will include 10 minutes of unloaded pedalling using a cycle ergometer. Volunteers will be asked to increase to their maximal pedal frequency possible for 1-2 seconds prior to applying a resistance of 5 % of pre-training body weight for the Wingate sprint. The sprints will take place at 2 minutes and at 6 minutes. Sprint duration will be increased from 10 seconds in the first week to 15 seconds in the second and third weeks and finally 20 seconds in the remaining weeks. Patients will receive strong verbal encouragement during the sprints after which the resistance will be removed. The acceptability of the training will be assessed with a questionnaire based on that used by Boereboom et al. in 2016. Participants in the control group will be asked to continue with their usual care and lifestyle activities.
Statistical Analysis
Data will be presented as mean ± standard deviation. Statistical analysis will be performed using SPSS statistical software. Paired sample T-tests will be used to analyse differences in pre- and post-intervention VO2MAX. Statistical significance will be accepted at p\<0.05.
