Date of Award
Doctor of Philosophy (PhD)
Schools and Centres
Research has identified a need to explore the components of exercise prescription for cancer survivors, particularly the most effective exercise intensity. The main purpose of this research was to examine whether exercise intensity modulates a range of physiological and psychological outcomes for breast and prostate cancer survivors. The primary outcomes were related to peak oxygen consumption (VO2peak) and quality of life (QOL). VO2peak is a highly sensitive measure that indicates overall health. QOL references the general wellbeing of individuals, and is an outcome of great importance in cancer rehabilitation research.
A pilot study involving breast cancer survivors (n = 19) and prostate cancer survivors (n = 12) was undertaken to determine the feasibility of delivering an eight-week group exercise and supportive group psychotherapy (SGP) intervention. Physiological (weight, body composition, cardiorespiratory endurance, and lower body strength) and QOL (using the Functional Assessment of Cancer Therapy questionnaire) outcomes were measured pre- and post-intervention in order to monitor program efficacy. The participants also provided feedback during group interviews after program completion in order to determine the acceptability of the program. Interpretative phenomenological analysis was used to analyse the feedback, determine the acceptability of the program and inform the main study design.
The pilot study recorded 90% retention and over 80% attendance rates for both components, indicating that the intervention was feasible for both breast and prostate cancer survivors. The results of the objective assessments of cardiorespiratory fitness and muscular strength indicated a basic efficacy of the intervention; however, they highlighted possible differences in response between the cancer types. In the feedback sessions, the participants described the contributions of both exercise and SGP to their feelings of wellbeing. The main themes that emerged were that the exercise facilitated the counselling sessions, and that the group bonding and sharing were the most important aspects of the program. The main changes to methodology from the pilot to the main study were to include a more sensitive cardiopulmonary fitness test, add measures of exercise motivation and physical activity levels, and add a follow-up assessment four months after completion of the post-intervention.
Main Study Methods
In the main phase of the research, breast cancer survivors (n = 72) and prostate cancer survivors (n = 87) were recruited. Those who enrolled in the group exercise and SGP intervention were randomised to a higher intensity group (HIG) (75 to 80% VO2peak and 65 to 80% one repetition maximum [1RM], n = 40) or lower intensity group (LIG) (60 to 65% VO2peak and 50 to 65% 1RM, n = 44). A control group of breast and prostate cancer survivors (n = 75) followed usual care. All the participants were assessed before and after the eight-week intervention or usual care. The intervention participants were followed up four months after intervention completion to monitor their ongoing physiological and psychological parameters and physical activity levels. The physiological assessments included cardiorespiratory fitness (ramped bicycle protocol), body composition (skinfolds), flexibility (shoulder goniometry and sit and reach test) and muscular strength and endurance (one repetition maximum leg press, push ups, and plank). The psychological assessments included questionnaires to assess QOL (Functional Assessment of Cancer Therapy), fatigue (Piper Fatigue Scale) and exercise motivation (Behavioural Regulations in Exercise Questionnaire version 2). The physiological assessments included cardiorespiratory fitness (ramped bicycle protocol), body composition (skinfolds), flexibility (shoulder goniometery and sit and reach test) and muscular strength and endurance (one repetition maximum leg press, push ups, and plank). The psychological assessments included questionnaires to assess QOL (Functional Assessment of Cancer Therapy), fatigue (Piper Fatigue Scale) and exercise motivation (Behavioural Regulations in Exercise Questionanire version 2). Their physical activity levels were also assessed via the International Physical Activity Questionnaire.
Program attendance for the HIG and LIG was approximately 90% for all planned sessions. The HIG had a high compliance (90%) to their target aerobic intensity; however, this was significantly lower (p < 0.001) than the LIG (97%). The LIG and HIG had similar increases in VO2peak (1.7 and 2.2 mL/kg/min, respectively), both of which were greater than the control group (p < 0.001). From post-intervention to follow up, the HIG increased 0.2 mL/kg/min while the LIG decreased 1.3 mL/kg/min (p = 0.021). The HIG decreased their body fat by 2.3%, which was significantly more than the control group (-0.3%; p = 0.002) but similar to the LIG (-1.1%; p = 0.37). The HIG increased the number of push ups they could perform by 6.6, which was significantly greater (p < 0.001) than both the LIG (+3.0) and the control group (+1.8). At follow up, the HIG and LIG both maintained their push up performance (p = 0.96). On the leg press test, the HIG increased their 1RM by 24.6 kg, which was significantly more than the control group (+8.9 kg, p = 0.007) but similar to the LIG (+14.4 kg, p = 0.16). From post-intervention to follow up, analyses indicated the HIG and LIG did not significantly differ on change in leg press 1RM (+3.8 kg and -8.6 kg, respectively; p = 0.08). No adverse events occurred in response to the higher intensity training.
There were no differences between the intervention arms and control group on changes in QOL from baseline to post-intervention. Similarly, there were no differences between the intervention groups on maintenance of QOL. Both intervention arms improved their exercise motivation specifically derived from meeting goals while the control group did not (LIG +0.4 points, HIG +0.3 points, control group +0.0 points; p = 0.004). The HIG maintained their motivation derived from both meeting goals and enjoying exercise at the follow up (no change for both), while the LIG returned to baseline levels (-0.3 points and -0.4 points, respectively; p = 0.047 and 0.007, respectively). All groups began with and maintained low levels of fatigue. All groups reported high levels of physical activity at baseline, and the intervention participants maintained these high levels at follow up. Although the participants maintained many improvements from post-intervention to follow up, regardless of intensity prescription, there were no further improvements from post-intervention to follow up. The breast and prostate cancer survivors attended and complied similarly with the intervention, and responded similarly on most physiological and psychological measures. The exceptions were that the breast cancer survivors improved their upper body muscular endurance and lower body strength by a greater magnitude than did the prostate cancer survivors. At the follow up, there were no significant differences in changes on any outcomes between the cancer types.
The results of this study suggest that higher intensity exercise provided greater long-term benefits to the breast and prostate cancer survivors for cardiorespiratory fitness, body composition and exercise motivation. Improved cardiorespiratory fitness and body composition have been directly linked to disease-free survival. There were no differences between the exercise and control groups for QOL or fatigue, thus indicating that this intervention did not successfully improve these psychological outcomes. The high level of physical activity by the control participants was unexpected, and probably mitigated some of the expected responses from the intervention. The breast and prostate cancer survivors responded similarly to the intervention on most physiological and psychological parameters.
The results of this study indicate that exercising at 70% of VO2peak and 65 to 80% 1RM provided greater long-term cardiorespiratory, body composition and exercise motivation maintenance than exercising at 61% VO2peak and 50 to 65% 1RM for breast and prostate cancer survivors. However, there were no differences between these exercise intensity levels for long-term influence on QOL. Measurable benefits can be achieved by exercising at higher intensities than previously prescribed.
Martin, E. (2014). The effect of exercise intensity on physiological and psychological outcomes in breast and prostate cancer survivors: a controlled study (Doctor of Philosophy (PhD)). University of Notre Dame Australia. http://researchonline.nd.edu.au/theses/85