Some personal info: I am MD and a specialist in sports and exercise medicine, have long experience in clinical work related to sports injuries, have published 150+ scientific papers related to physical activity, sports and health in international peer-review journals, have worked since 2004 as a professor of sports and exercise medicine in the University of Jyväskylä.
Role of exercise in chronic disease management
Traditionally physical activity has been regarded as a powerful tool in the prevention of many chronic diseases. It has been widely accepted that an epidemiological observational study with supportive data from studies on disease mechanisms give enough evidence for exercise recommendations in disease prevention. Final evidence for the benefits of exercise in the treatment of patients with chronic disease using limited resources of health care system should optimally be based on well designed randomized controlled trials (RCTs). Recently, the number of RCTs evaluating the effects of physical exercise therapy in the treatment of specific diseases has increased substantially.
The most consistent finding of the studies is that exercise capacity or muscle strength can be improved among patients with different diseases without causing detrimental effects on disease progression (Kujala 2004). Severe complications in the exercise trials were rare. In some diseases, such as osteoarthritis, pain symptoms may also be reduced. The majority of the RCTs are of a too short duration to document disease progression. Studies on patients with coronary heart disease as well as studies on patients with heart failure show that exercise groups have somewhat reduced all-cause mortality. The clinically very significant findings include that exercise therapy has beneficial effects on all metabolic syndrome components and is highly beneficial for the patients with type 2 diabetes mellitus.
Before interpreting detailed results of studies, critical analysis of the methodological quality of the individual RCTs is important. Also, we have to keep in mind that generalizability may be a problem while some RCTs include patients that are not representative of the general population of patients as regard to age and coexisting diseases.
The fact that most trials are of short duration means that some benefits, such as increases in physical fitness, are reached within some weeks or months. However, the duration of specific RCTs usually is too short to give final evidence on the effects of exercise therapy on the true progression of disease. RCTs on the effects of exercise on the lipid risk factors, blood pressure levels, glucose homeostasis, as well as sporadic long-term follow-ups of disease progression support the conclusion that exercise therapy may have a beneficial effect on the long-term progression of specific diseases. However, there is a need for RCTs with long-term follow-ups including documentation of such outcomes as survival rate, hospitalization rate, and health care costs.
Physicians prescribing exercise therapy have to know basics of exercise physiology and training principles. Also, tailoring of a program depends on the disease and its stage, baseline fitness level of the patient, and goals of the program set together with the patient.
The available RCTs include rather large variety of effective training programs. Majority of the patients seem to benefit from low to moderate intensity aerobic exercise. Based on the available RCTs detailed conclusions on the dose-response of exercise therapy in the treatment of specific diseases can not be done. We have to remember that beneficial results of exercise therapies for patients with chronic disease shown by RCTs are based on carefully planned and followed exercise interventions among patients whose clinical status has first been examined to take into account possible risks. Unlike in young healthy persons, in the prevention of disease the therapeutic range of physical activity may be narrow among individuals with chronic disease. In exercise therapy long-term adherence is a general problem. In clinical work we have to take into account that correction of other modifiable risk factors such as diet and smoking are also important, as is the optimal medication.
Kujala UM. Evidence for exercise therapy in the treatment of chronic disease based on at least three randomized controlled trials – summary of published systematic reviews. Scand J Med Sci Sports 2004;14:339-345.
Taylor RS, Brown A, Ebrahim S, et al. Exercise-based rehabilitation for patients with coronary heart disease: systematic review and meta-analysis of randomized controlled trials. Am J Med 2004;116:682-692.
Smart N, Marwick TH. Exercise training for patients with heart failure: a systematic review of factors that improve mortality and morbidity. Am J Med 2004; 116: 693-706.
Thomas DE, Elliot EJ, Naughton GA. Exercise for type 2 diabetes mellitus. Database of Cochrane Systematic Review, 2007.