Exercise as it relates to Disease/The role of exercise training in cancer survivors

The following is a critical analysis of the journal article 'Cancer treatment-induced alterations in muscular fitness and quality of life: the role of exercise training'. This analysis has been written for a university assessment in the unit Health, Disease and Exercise.

What is the background to this research?
Cancer is a debilitating condition which accounted for 19% of the total disease burden in Australia in 2011 and causes a total of 131 deaths every day. Cancer is associated with poor quality of life, premature mortality and a range of other physiological, social and psychological impairments. Patients are usually subjected to various drugs for cancer treatment and its side effects, however the promotion of exercise as an alternative or adjunct therapy is receiving increasing support. Exercise has the potential to improve health without some of the extreme side effects experienced from pharmaceutical interventions. Many researchers and health professionals are beginning to consider the benefit of exercise as a treatment and preventative measure for not only cancer but also other chronic diseases such as type II diabetes, hypertension and cardiovascular disease. As cancer has varied effects on individuals, it has been noted generalized exercises interventions have the potential to cause negative side effects, emphasizing the importance of implementing individualized programs.

Muscular weakness is one chronic side effect that is commonly reported in cancer survivors. Muscular weakness is caused by muscle wastage (also known as catabolism) – involving a decline in protein synthesis, muscle cross sectional area and loss of proteins important for energy production. Muscle catabolism is usually caused by physical inactivity and other physiological factors that impair engagement in exercise. This muscle catabolism and consequent weakness reduces mobility, flexibility and quality of life in cancer patients, impacting motivation and physical capability to exercise. This article considers the effects an exercise intervention has on reducing muscle breakdown and improving other health measures in a sample of cancer patients.

Where is the research from?
This study was conducted by researchers from the Rocky Mountain Cancer Rehabilitation Institute, University of Northern Colorado, National Hsin Chu University of Education and Regional Breast Centre of Northern Colorado. The study was published in the Annals of Oncology in September 2007, which has an impact factor of 11.85 and is currently sitting at 10th in its field.

What kind of research was this?
This research was an observational pre-post study design, which involves taking measures prior to the intervention and then re-assessing the same measures post-intervention. A pre-post study design is a level three research method and is considered less reliable than randomised control trials. The main disadvantage of using a pre-post study design is the lack of comparison to a control group who remain untreated, therefore changes observed cannot be entirely attributed to the intervention. Despite this, a pre-post study is a simple and effective way to track individual changes over time.

What did the research involve?
A sample of 114 breast cancer and 21 prostate cancer survivors were referred by their oncologists to participate in this study. 114 patients had completed treatment, while 21 were still undergoing treatment. Types of treatment included: radiation, chemotherapy and surgeries, or a combination of all three. A comprehensive medical and cancer screening was undertaken prior to the exercise intervention, followed by various physiological and psychological assessments. Blood pressure, heart rate and oxygen saturation were monitored throughout these assessments.

Individualized exercise programs were then developed and implemented by certified exercise specialists who had previous experience with cancer rehabilitation. The exercises sessions were conducted on up to three non-consecutive days per week over six months and typically involved a short warm up, followed by 40 minutes of strength, aerobic and flexibility training and a short cool down (60 minutes total). Exercises progressed from light weight resistance-band activities to more complex machine and free weight exercises (as tolerated). Intensity was prescribed according to rating of perceived exertion and percentage of heart rate reserve. The researchers hypothesized an increase in both physiological and psychological variables after six months.

What were the basic results?
The study found improvements in most areas of muscular fitness, depression, quality of life and social quality of life. Positive effects were seen after participating in aerobic exercise, including an increase in mitochondrial size and oxidative enzymes, boosting the levels of energy (ATP) for muscular work. Resistance training was also beneficial in increasing muscle cross-sectional size and force production. Improved or maintained muscular fitness was observed in all participants.

Limitations
Treatment stages varied – 21 patients were still undergoing treatment and 114 had completed treatment or surgery within the last 25 months. Groups were unequal in numbers and there was a lack of randomization. A small sample size reduces the validity and reliability of results, and a lack of a control group also makes it difficult to determine whether all changes were attributed to the intervention.

What conclusions can we take from this research?
Despite there being two different types of cancer patients at different stages of treatment, positive effects were observed in all participants - indicating exercise was beneficial regardless of the cancer type. Future research is needed to determine the optimum intensity, duration and type of exercise suitable for cancer patients. Few studies have investigated the effects of resistance training and this is another area suggested for future research.

Practical advice
This article suggests exercise is an effective way to enhance health in cancer survivors. Other studies also support the combination of aerobic and resistance exercise in improving quality of life, depression and anxiety.

There is a clear association between obesity and an increased risk of endometrial, liver, gallbladder, breast, pancreatic, esophageal and colorectal cancers. This highlights the importance of exercise as not just a treatment for cancer and its side effects, but also as a preventative measure in otherwise healthy populations.

Cancer patients are a unique population and responses to exercise will vary significantly, however there is a growing body of research supporting low-moderate levels of exercise. Future research should continue to compare aerobic, resistance and combined exercise treatment to determine the best modality for improvements in health in cancer survivors. Cancer patients wishing to begin an exercise program should consult a health care professional.