Writing the Exercise Prescription – Alisa H. Darling, MD
Through multiple studies, the benefits of exercise are well known. Regular physical activity has been shown to reduce the risk of developing cancers, Type 2 diabetes, Alzheimer’s dementia, and to reduce the incidence of heart disease and stroke. If benefits of exercise and physical activity were available in pill form, it would likely be the highest selling medication in the U.S.
However, despite the known benefits of exercise, physical activity levels are not regularly part of the physician visit. One study revealed that only a third of U.S. patients reported receiving exercise counseling at their last doctor’s visit [i]. In fact, we might not be counseling our patients due to our own inactivity. Another recent study showed that 40% of primary care doctors and medical students failed to meet the 2008 Physical Activity Guidelines from the CDC[ii]. These numbers need to be improved because exercise advice specifically recommended by a physician is much more likely to be heeded.
THE HEALTH BENEFITS OF EXERCISE
Regular physical activity is widely advocated for its benefits to the musculoskeletal, endocrine, cardiovascular systems.
Type 2 Diabetes has reached epidemic levels in the United States with over 24 million people having the disease. An additional 60 million may be prediabetic. [iii] Although regular physical activity may prevent or delay diabetes and its complications, most with the disease are not active. The effects of exercise include improved blood glucose uptake into muscle tissue via a mechanism that is not impaired by insulin resistance during muscle contraction as well as improved insulin action that continues even after exercise session is done. Therefore, people with T2DM should be performing at least 150 minutes of PA per week. In addition, the ACSM and ADA both recommend 2.5 hours of moderate to vigorous physical activity per week for people at high risk for developing the disease. This recommendation is a significant part of lifestyle changes recommended.
Regardless of the participants’ age, race and gender, regular physical activity and fitness has been shown to improve cardiovascular risk and lower mortality rates in the healthy as well as in the PVD/CAD and diabetic populations. With concomitant weight loss, cholesterol levels improve, as does blood pressure[iv]. In addition, systemic inflammation is reduced.
Another well-established group of benefits resulting from regular physical activity is that for the musculoskeletal system. As we age, we lose muscle power and strength, balance, and bone density. Aerobic training leads to increased maximal aerobic capacity and decreased large artery stiffness. Resistance training increases muscle mass and power. Enhancing these factors is associated with increased ability to perform self-care, housework and outdoor activities, especially important in the aging population.
In addition to advances in function, regular exercise can lead to better bone health. Regular weight bearing PA has been shown to lessen the age-related decline in bone mineral density and to increase peak bone mineral mass in children and adolescents. Even the frailest patients should be as active as their health allows due to the rapid decline in BMD seen during bed rest and inactivity. In addition to that expected from lessening the degree of osteopenia/osteoporosis, exercise has been shown to reduce the incidence of bone fractures due to improved balance, flexibility and decreased in fall risk.
The effects that regular exercise has on well-being and psychosocial health has been well documented. [v] Aerobic exercise can lead to several hours of anxiety reduction. It can also lead to improvements in school and work productivity.[vi]
In addition to improvements in mood, exercise can lead to improvements in cognitive performance, especially in executive functioning.
As physicians and health care providers, we are often called upon to prescribe therapeutic exercise to improve function and decrease pain after sports injuries, for chronic pain, after stroke, for gait difficulties, etc. However, an exercise prescription should now be generalized to a population for the treatment of inactivity and obesity and prevention of and treatment for their related conditions.
A familiar way to encourage patients to increase their physical activity is to use something we write everyday…the prescription. By using the FITT principle, an exercise prescription can be written in a way that is similar to a typical medication prescription. FITT is the abbreviation for Frequency, Intensity, Time and Type.
According to the Physical Activity Guidelines for Americans for general health maintenance, most adults should be performing 2 hours and 30 minutes of moderate intensity cardiorespiratory exercises weekly.[viii] This total has been broken down to 30 minutes, 5 days weekly. An alternative recommendation is for vigorous intensity activity for at least 20 minutes, three days weekly. The American College of Sports Medicine also recommends 2-3 days of resistance-based exercises that work all muscle groups, including arms, legs and trunk.
Frequency refers to the number of times that the exercise is performed. The recommendations for maintenance range from 3-5 days weekly. However, there is leeway in prescribing frequency of activity. The most important factor to consider is the patients’ ability to achieve this goal safely and practically given their current lifestyle and time constraints. One principle that is consistent is that the frequency can be increased over time to achieve maintenance or weight loss goals. It is not practical or safe for a person to perform all 150 minutes in one session weekly.
Adults should be encouraged to progress resistance training to work major muscle groups 2-3 days per week.
The intensity of a workout refers to how hard the body needs to work to perform the exercise. It is an important factor to consider when writing the prescription because it may lead to adverse event. Though low and moderate intensity activities can typically be recommended safely, high or vigorous activity should be evaluated more closely.
Patients can and should be taught how to judge the intensity of their activity. There are different ways to gauge cardiovascular exercise intensity. Absolute measures have been developed; the most common is the MET or metabolic equivalent. The levels range from low (<3 METs) to vigorous (>6 METS). However because people of different ages, weights, strengths and fitness levels exist, absolute measures of intensity cannot predict how the activity is tolerated.
Therefore, relative measures of intensity are more useful. The Talk test is an effective prescriptive tool.[ix] Light intensity exercise allows the patient the ability to talk and sing comfortably. Moderate intensity allows talking but not singing. Finally, vigorous activity allows neither conversation nor singing.
Patients who are at higher risk with physical activity should still be encouraged to be active. However, they require closer monitoring and supervision. Percentage of heart rate reserve and maximal heart rate can be used. If deemed necessary, these and other physiological measures can be used in a monitored setting (i.e. cardiac rehabilitation) to allow physical activity.
Muscle strengthening activities are an important component of an exercise prescription. Again, however, the recommended “moderate to high level” of intensity can be difficult to judge. The muscles need to work in order for the patient to achieve benefit. However, intensity varies between persons depending on previous activity level, gender, age, etc. The patient should choose a weight that allows them to perform 8-12 repetitions but forces them to fatigue the muscle [x].
For aerobic activity, the weekly recommendations total 150 minutes for health maintenance. They increase to 250 minutes per week for significant weight loss [xi]. Physical activity should be performed on a daily basis though 5 days per week is thought to be acceptable. The exercise sessions do not need to be in a continuous session. Multiple shorts bouts of exercise of 10 minutes are thought to be beneficial.[xii]
Resistance training should progress to 8-12 repetitions x 2-3 sets.
The type of exercise performed should be discussed with the patient. The best type of exercise is one which the patient can and will perform regularly. It should be appropriate given the patients’ interests, finances, and lifestyle. There should be some variety to limit overuse activity. Simple exercises such as walking or using body weight for resistance training are often the best choices. If people are able to incorporate these activities into their everyday life (gardening, walking or biking to work, using a walk-behind mower), they are more likely to maintain activity.
Whether because of fatigue, discomfort or lack of confidence in their ability, people who push or who are pushed too hard when beginning an exercise program often do not continue their activity. Therefore, it is important to have a discussion with your patient about where to start. The issues that should be addressed include the level of activity that the patient will perform and the amount and intensity that the physician feels is safe given the patient’s current activity level and health history. The recommendations should be modified as the patient’s health, activity level and tolerance changes.
A program of regular physical activity is essential to maintain and improve the health and function of most adults. The benefits of exercise far outweigh the risks of injury. Even the most disabled or frail adults can achieve the goals stated, with the evaluation and guidance of trained medical professionals. The exercise program, or prescription can be modified to fit the health, physical ability, and lifestyle of the patient. In addition, as these factors change, the plan can be adjusted.
[i] Wee CC, McCarthy EP, Davis RB et al. Physical counseling about exercise. JAMA 1999, 282: 1583-1588
[ii] Lobelo F, Duperly J, Frank E, Physical Activity habits of doctors and medical students influence their counseling practices. British Journal of Sports Medicine 2009; 43:88-92
[iii] ACSM and ADA Joint Position Statement. “Exercise and Type 2 Diabetes”. Medicine & Science in Sports & Exercise. 2010; 142:2282-2296.
[iv] Ibid, 2287.
[v] Gaz DV and AM Smith. PM&R 2012 4: 812-817
[vi] Raglin JS. Exercise and Mental Health, Beneficial and Detrimental Effects. Sports Med. 1990; 9: 323-329
[vii] Concannon LG, Grierson MJ and MA Harrast, PM&R 2012 4:833-839
[viii] Garber CW, Blissmer, B, et al, ACSM Position Stand Quality and Quantity of Exercise for Developing and Maintaining Cardiorespiratory, Musculoskeletal and Neuromotor Fitness in Apparently Healthy Adults: Guidance for Prescribing Exercise. Medicine and Science if Sports and Exercise; 2011; 1334-1349
[ix] Philips EM and Kennedy MA, The Exercise Prescription: A Tool to Improve Physical Activity. PM&R, 2012; 4: 818-825
[x] Philips EM and Kennedy MA, 2012.
[xi] Donnelly JE, Blair SN, et al. Appropriate Physical Activity Intervention Strategies for Weight Loss and Prevention of Weight Regain for Adults. Medicine and Science in Sports & Exercise. 2009: 459-467.
[xii] Philips EM and Kennedy MA, 2012.