Exercise as it relates to Disease/Effects of exercise on three common cancers

This is a critique of the article: Effects of exercise on physiological and psychological variables in cancer survivors.

What is the background to this research?

There are many detrimental effects that cancer has on the body, including fatigue, nausea, bone loss and digestive problems. The positive effects that exercise can have on cancer during and after treatment are becoming widely recognised. Such benefits include reduced fatigue, improved quality of life and reduced disease-symptoms.

This study set out to investigate physiological and psychological variables including Vo2 max, body composition, measures of fatigue and quality of life, and how they were affected by exercise. The study was also designed to compare the outcomes of low intensity with moderate intensity to determine the most effective form of exercise.

Where is the research from?

The research was conducted in Oregon, USA. Given that this study was conducted within a Western society, it is likely to be applicable to other Western societies such as Australia.

The paper was published in 2002 authored by Timothy Burnham, a PhD student and Anthony Wilcox, a professor of Physical Education. Wilcox served as the head of the Exercise and Sports Science department at Oregon State for many years and appears to be well known and respected due to his position in the field. This was Burnham’s first study into this area, so it is unlikely that he had reason to overestimate the results. However, Wilcox’s experience and expertise in the field may lead to bias when interpreting the results.

What kind of research was this?

The study conducted was a Randomised Control Trial, which is considered to be the most reliable form of study, particularly in health sciences. However, there is still the possibility of participant bias. Particularly in this study, many of the variables measured were subjective, and the control group were not blinded. This may have influenced the responses to the subjective based questions following the intervention. There is also the possibility that the participants in the exercising groups had an understanding of the benefits of exercise overall, which may have influenced their responses. A participant’s expectations regarding exercise greatly influences the psychological benefits achieved by the individual.

What did the research involve?

This study investigated 21 patients suffering from either breast, colon or lung cancer. There were no requirements as to whether or not they were already undergoing treatment for their cancer. This introduced other independent variables that were not considered in the overall results. Each participant was randomly assigned to one of three groups; control group (no exercise), low intensity exercise, or moderate intensity exercise. All participants completed a questionnaire to ensure they were not currently participating in physical activity, to ensure that this would not affect the results.

Physiological variables including Vo2 max, flexibility and skin folds were assessed prior to the commencement of the program. Participants also completed the Quality of Life Index for Cancer Patients, and the Linear Analog Self-Assessment. The participants undertook a 10-week supervised exercise program of either low or moderate intensity. Variables were assessed at the end of the 5th and 10th weeks, however, comparisons were only made using the final outcomes, with little discussion of the comparisons from mid-way to the final outcome.

As discussed above, the participants in the control group knew that they were not undertaking the exercise, which may have caused a bias in the results of the subjective values. The sample size of 21 subjects also poses limitation when evaluating the findings. Small sample sizes suggest that results may not be indicative of the broader population. This study also only looked at people suffering from three types of cancer. There is the possibility that results may have varied if the participants were suffering from a more advanced form of cancer.

What were the basic results?

No differences in physiological variables between the 2 exercise groups were evident. Due to this, both exercise groups were combined into one to compare to the control group. Significant differences were seen in all physiological variables when compared to the control group. Measures of psychological variables also improved.

Despite the positive results, there were still certain variables that were not considered. For example, some of the participants were undergoing other treatment for their cancer, whilst others were not. This may affect the findings as it is difficult to determine whether the positive results are due to the exercise intervention, or another form of treatment not considered.

What conclusions can we take from this research?

Based on the results of this research, it appears that the positive effect of exercise on both the physiological and psychological variables of the participants was significant. This research also concluded that low intensity exercise is just as beneficial as moderate intensity exercise in improving all studied variables. However, this conclusion may reflect more the limitations of the study and not be an accurate representation of the effects of exercise intensity.

Firstly, the study only involved 21 participants, with different forms of cancer, who may also be undergoing further treatment for their cancer. These factors may have a large influence on the outcomes of this research due to the introduction of independent variables that were not considered.

Furthermore, the duration of the program may not have been long enough to accurately reflect the effects of different exercise intensities. A longer duration exercise program would allow researchers to evaluate the chronic adaptations to exercise, and not just the acute changes that would appear in this shorter program. A longer duration study may be necessary before concluding that there are no differences between intensities.

The researchers acknowledge the limitations of this study and recognise that further research involving longer programs and a broader range of cancer survivors is required.

When comparing the results of this study with wider literature involving cancer and exercise, it is clear that there are measurable benefits that exercise has on cancer. However, more research into the effects of different exercise intensities is required.

Practical advice

Despite the need for further research into exercise intensities, based on this research suggesting that low intensity exercise is just as beneficial, it may be best to prescribe exercise at an intensity that the client is able to maintain. Better results may be achieved if the client adheres to a low intensity program, rather than aiming for a high intensity program that is unachievable and therefore not maintained.

The Australian Association for Sport and Exercise Science position statement regarding cancer and exercise, as well as the exercise and cancer guidelines can be accessed here.

Further information/resources

For more information regarding cancer and the benefits of exercise please visit:

Department of Health: Cancer facts and figures

Cancer Council: Exercise and cancer

Exercise Right: Cancer

Clinical Oncology Society of Australia: position statement on exercise in cancer care

For information on exercise groups across Australia please visit:

Breast Cancer Network Australia: exercise programs