The Benefits of Exercise During and After Cancer Treatment
by Lee W. Jones, PhD
The therapeutic properties of endurance and resistance exercise have been recognized since antiquity. In 1995, the American College of Sports Medicine, together with the U.S. Centers for Disease Control and Prevention, published the first exercise guidelines to encourage increased exercise in Americans of all ages for health promotion and disease prevention. These guidelines were based on remarkable data from epidemiological studies showing that regular moderate-to-vigorous exercise reduces the risk of cardiovascular disease by one-third, whereas high levels of cardiorespiratory fitness may reduce these risks by up to 60 to 70 percent.
Unfortunately, investigation of the role of exercise following a diagnosis of cancer has received comparably less attention. In the past decade, however, examination of the role of exercise following a cancer diagnosis, a field researchers have termed “exercise oncology,” is becoming increasingly recognized as a legitimate and important field of research in cancer management.
Exercise During Therapy
Cancer therapy is associated with various degrees of damage to the cardiovascular system (lungs, heart, skeletal muscle) that also occur in the presence of significant reductions in usual levels of physical activity, which leads to deconditioning, weight gain, and loss of muscle mass. In combination, these effects dramatically reduce a person’s ability to tolerate exercise and normal activities of daily living, such as gardening, housework, and shopping, and can increase susceptibility to other conditions, like diabetes, cardiovascular disease, and arthritis.
Several ongoing trials are being conducted to identify the optimal type, intensity, duration, and frequency of exercise needed to mitigate treatment late effects in cancer survivors.
To address these concerns, researchers in the mid-to-late 1980s initiated the first studies to explore whether structured exercise training may be an appropriate intervention to mitigate treatment-induced toxicities and anticipated loss of cardiorespiratory fitness among women with early-stage breast cancer. Since these early studies, more than half of the exercise studies in people with cancer have been conducted during therapy. Overall, the current research provides promising evidence that exercise training is a well-tolerated and safe intervention that can mitigate several common treatment-related side effects, including fatigue, deconditioning, nausea, anxiety, and loss of muscle strength.
Exercise After Therapy
Over the past decade, exercise has emerged as an integral aspect of cancer survivorship and preventing or treating the late effects of therapy. Similar to during therapy, clinical trials in this setting have provided strong evidence that exercise is a well-tolerated and safe intervention associated with significant improvements in cardiorespiratory fitness, fatigue, and quality of life in cancer survivors. Most of these studies have examined the effects of either aerobic training alone, resistance training alone, or the combination of aerobic and resistance training in cancer survivors. Several ongoing trials are being conducted to identify the optimal type, intensity, duration, and frequency of exercise needed to mitigate treatment late effects in cancer survivors.
A major point of interest in exercise-oncology research is establishing whether the benefits of exercise extend beyond symptom control to improving longevity in cancer survivors. Several landmark observational studies have provided the first evidence that regular exercise (such as brisk walking for 30 minutes a day, 5 days a week) is associated with 15 percent to 61 percent reductions in the risk of mortality following a diagnosis of early-stage breast or colorectal cancer, relative to survivors who were inactive.
It is becoming increasingly evident that sedentary behavior and decreased exercise levels following a cancer diagnosis can increase treatment-related toxicities, whereas engaging in regular exercise can significantly reduce the incidence and extent of such toxicities. Current guidelines recommend that cancer survivors participate in at least 150 minutes of moderate exercise (such as brisk walking or light swimming) or 75 minutes of vigorous exercise (such as jogging, running, or hard swimming) per week. However, this is considered the minimal amount of exercise required to derive health benefits. Increases in exercise beyond these levels are associated with greater health benefits.
The field of exercise oncology is rapidly evolving with many unanswered questions; nevertheless, the current evidence base provides a clear indication that exercise is an additional powerful weapon in the fight against, and recovery from, cancer.
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Dr. Lee Jones is an associate professor in the department of Radiation Oncology and is research director of Cancer Survivorship at Duke University Medical Center in Durham, NC.
Speak with your doctor before beginning any exercise plan. Your doctor can help you decide what types of exercise will be beneficial for you.
This article was originally published in Coping® with Cancer magazine, January/February 2011.