INTRODUCTION — Regular exercise has been shown to have wide-ranging health benefits. There is evidence to suggest a sedentary lifestyle may be an even stronger predictor of mortality than such established risk factors as smoking, hypertension, and diabetes . Numerous epidemiologic studies show that unfit individuals are two to three times more likely to die during follow-up compared with their more fit counterparts, regardless of their risk profile, body habitus, or the presence of cardiovascular disease. Because physical inactivity is a modifiable risk factor, clinicians should routinely assess and prescribe structured exercise and increased lifestyle activity to all patients .
In this topic, we discuss how to prescribe a beginning exercise program, ensure that exercise is safe and effective, and provide guidance about increasing exercise intensity and volume. Additional discussions of the fundamental concepts of exercise and exercise in the setting of particular conditions and disease states are found in a number of UpToDate topics, including the following:
●Benefits and risks, patient assessment, and medical clearance (see "Exercise for adults: Terminology, patient assessment, and medical clearance" and "Physical activity and exercise in older adults")
●Aerobic exercise (see "The benefits and risks of aerobic exercise")
●Resistance exercise (strength training) (see "Strength training for health in adults: Terminology, principles, benefits, and risks" and "Practical guidelines for implementing a strength training program for adults")
●Exercise and cardiovascular disease (see "Exercise and fitness in the prevention of atherosclerotic cardiovascular disease" and "Cardiac rehabilitation programs" and "Exercise in the treatment and prevention of hypertension")
●Exercise and obesity (see "Obesity in adults: Role of physical activity and exercise")
●Exercise and diabetes (see "Exercise guidance in adults with diabetes mellitus")
●Exercise and coronavirus disease 2019 (COVID-19) (see "COVID-19: Clinical features", section on 'Physical inactivity' and "COVID-19: Return to sport or strenuous activity following infection")
TYPES OF EXERCISE AND RELATED CONCEPTS — When prescribing an exercise program, it is helpful for the clinician to understand the different types and basic concepts of exercise. These are reviewed separately. (See "Exercise for adults: Terminology, patient assessment, and medical clearance", section on 'Terminology and common types of exercise' and "Strength training for health in adults: Terminology, principles, benefits, and risks".)
PRESCRIBING AN EXERCISE PROGRAM — Primary care clinicians can help their patients begin exercising or advance their exercise program through encouragement and by providing a plan to follow .
Components of an exercise program — Ideally, an exercise program should include exercises that improve cardiorespiratory fitness, strength, and mobility . Some programs and individual exercises allow two or more of these components to be developed simultaneously.
●Aerobic exercise is a general term, often referred to as endurance training, and includes any activity that develops cardiovascular and pulmonary fitness. It is an important component of an exercise prescription with an abundance of evidence supporting its benefits for health [4-6]. (See "The benefits and risks of aerobic exercise".)
●Strength exercises provide important health benefits beyond aerobic activity. Also referred to as resistance training, strength training can be performed using bodyweight resistance (eg, push-ups (picture 1)), free weights (eg, barbell squats (picture 2)), or other tools (eg, machines (picture 3) or resistance bands (picture 4)) that place loads on muscles, forcing them to work harder. The best programs emphasize multijoint exercises such as the squat, deadlift, and press, which involve all the major muscle groups, working them through a full, functional range of motion. Strength training is typically done two or three days per week. (See "Strength training for health in adults: Terminology, principles, benefits, and risks" and "Practical guidelines for implementing a strength training program for adults".)
●Mobility exercises are important for maintaining functional capacity. Particularly among older adults, mobility is important for performing activities of daily living and avoiding falls. The goal of mobility work is to maintain a healthy range of motion, particularly at the shoulders, hips, and thoracic spine. However, separate mobility exercises are not needed for all individuals, particularly those who regularly engage in activities that involve full motion at the major joints. Time spent performing isolated flexibility exercises is not counted towards the weekly goal of 150 minutes or more of moderate-intensity exercise. While flexibility exercise is recommended by such groups as the American College of Sports Medicine (ACSM), systematic reviews have found no evidence to support this form of training for reducing injury [7,8].
If stretching exercises are performed to increase muscle flexibility, it is usually best to do so after aerobic or strength workouts when muscles are warm. Studies of stretching have failed to demonstrate benefits in the form of reduced injury rates or improved functional status, but many people feel their movement is enhanced by following a stretching regimen. Stretching is best done using slow and steady movements, rather than bouncing (so-called ballistic stretching). Functional movement activities such as yoga (picture 5), Pilates, and tai chi (movie 1) improve flexibility, balance, and mobility. (See "Overview of yoga".)
●Warm-up/cool-down – In addition to the components described above, moderate and vigorous exercise is best preceded by a warm-up and followed by a cool-down period. A warm-up usually involves doing the planned exercise at a lower intensity and speed and allows the body to prepare for more vigorous activity. A cool-down is done to aid recovery and, following vigorous exercise, can prevent exercise-associated postural hypotension and its manifestations (eg, lightheadedness, syncope). (See "Exertional heat illness in adolescents and adults: Management and prevention", section on 'Heat syncope and exercise associated collapse' and "Preparation and management of mass-participation endurance sporting events", section on 'Exercise-associated postural hypotension'.)
Writing the aerobic exercise prescription — All previously inactive patients should begin exercising at a light to moderate intensity and increase this intensity gradually, over weeks to months, provided they remain asymptomatic and that their perceived exertion (RPE) remains below 15 (table 1), signifying "hard work." A typical exercise prescription can be created using the FITT mnemonic :
●Frequency: Number of days per week (ideally three or more)
●Intensity: Moderate or greater (achieved gradually)
●Time: Number of minutes per session (ideally 30 minutes or longer)
●Type: Aerobic activity of choice (eg, walking, jogging, cycling)
Important aspects of each component of the aerobic exercise prescription are discussed below. An example of a prescription for a beginning exerciser is provided (table 2) along with an exercise prescription template from the Exercise is Medicine initiative (EIM exercise Rx). Additional sample exercise prescriptions for strength training and patients moving beyond the initial stages of aerobic exercise are provided below. (See 'Writing the strength training exercise prescription' below and 'Helping patients advance their exercise program' below.)
●Frequency – Abundant evidence suggests that spreading the total weekly time for aerobic exercise across three or more days produces consistent health benefits and decreases the risk of injury . Whenever possible, we recommend exercising three or more days per week. If this is not feasible, exercising for the same total period over two days (75 minutes each day), or possibly even one day (150 minutes), may provide equivalent health benefits . However, the risk of musculoskeletal injury, particularly from overuse, may be increased by doing so.
Epidemiologic, observational, and randomized controlled trials have examined the impact of exercise frequency, either per day or per week, as a function of health-fitness outcomes. As an example, in one trial, subjects who were randomly assigned to one of three groups that ran the same total distance, but in one, two, or three sessions daily, demonstrated comparable improvements in cardiovascular endurance . In another trial, 56 females with a body mass index (BMI) between 30 and 38 were randomly assigned to either repeated, short exercise bouts (n = 28) or one continuous bout (n = 28), and followed for 20 weeks . Each group exercised five days per week. Although both groups made comparable improvements in functional capacity, the repeated short-bout exercise group demonstrated better adherence and a greater average weight loss, 8.9±5.3 kg versus 6.4±4.5 kg.
●Intensity – Increasing the intensity of aerobic exercise can produce similar benefits in a shorter period. As an example, 15 minutes of jogging appears to confer the same health benefit as 30 minutes of moderate-intensity walking.
In addition to the conventional methods described separately, the "talk test" is a simple way to gauge exercise intensity . During moderate-intensity exercise, a person is too winded to sing, but not so winded they cannot talk. During vigorous exercise, a person has difficulty maintaining a conversation. (See "Exercise for adults: Terminology, patient assessment, and medical clearance", section on 'Determining exercise intensity'.)
●Time – The time required for aerobic exercise each week depends on both frequency and intensity. Benefit can be accrued in many ways, and a flexible approach is encouraged. Bouts of exercise can be performed in 30- to 60-minute blocks or accumulated throughout the day in 5- to 10-minute periods. (See 'Improving compliance with a basic aerobic exercise program' below and 'Strategies for incorporating exercise into the workday' below.)
The 2018 Physical Activity Guidelines recommend the equivalent of 150 minutes per week of moderate to vigorous aerobic activity each week, with muscle-strengthening activities on two days during the week . However, these guidelines and other seminal studies support the assertion that some physical activity is better than none [4,14,15].
A systematic review of 19 studies involving 1080 adults participating in moderate-intensity exercise (walking in most studies) concluded that continuous and accumulated exercise (ie, several bouts of approximately 10 minutes each) produced comparable effects on fitness, blood pressure, and blood biomarkers of health . Earlier studies reported that three 10-minute bouts of exercise performed throughout the day provide similar health benefits to a single, continuous 30-minute bout of moderate exercise [3,17,18], and subsequent studies suggest that even shorter periods of light to moderate physical activity, accrued over time, can produce cardiovascular, metabolic health, and even survival benefits [19-21]. Evidence accumulated over a decade from reliable, wearable fitness trackers confirms the importance of accumulated bouts of very short-duration physical activity (ie, one- to two-minute bouts) [22,23]. In a prospective observational study involving over 400,000 subjects, researchers found that even 10-minute bouts of daily moderate activity were associated with nearly a 10 percent reduction in all-cause mortality . Collectively, these data support the hypothesis that, when it comes to exercise, every minute counts.
While more than 150 minutes per week of moderate- to vigorous-intensity exercise may provide some additional health benefit, returns on the investment diminish as the time spent increases. As an example, in the large observational study described above, the maximum mortality reduction associated with regular, vigorous physical activity approached 45 percent and appeared to plateau between 40 and 50 minutes of daily exercise . For the typical adult seeking to improve their general health, it is unlikely that much is gained by exercising at a moderate intensity for longer than 100 minutes per day.
●Type – A wide range of activities can be used to achieve exercise goals. Walking is often considered the default activity for a beginning aerobic exercise prescription because it is simple, requires no equipment, and is easily measured by time, distance, or step count. Fast walking for 30 minutes generally correlates with ambulating approximately 4000 steps or 2 miles (3.2 km). Guidelines suggest a reasonable total daily step count goal for adults is 7000 to 10,000 .
Regular walking is highly beneficial for most inactive, unfit subjects . In a large prospective observational study, subjects who walked just 15 minutes per day or 90 minutes per week had a 14 percent reduction in mortality over an average follow-up of 8.1 years compared with their inactive counterparts . In a similar study of 2110 middle-aged male and female participants, those taking 7000 steps or more per day had a 50 to 70 percent lower mortality over the 10.8-year follow-up period than those taking fewer than 7000 steps per day .
Although walking may be easiest for beginning exercisers, any comparable activity performed at a moderate pace and for the same total duration provides similar health benefits to brisk walking. Activities such as bicycling, water aerobics, doubles tennis, ballroom dancing, or gardening can be done to satisfy weekly exercise goals.
Once regular moderate exercise has been made a habit, patients can be encouraged to incorporate more vigorous forms of activity into their program, provided they remain asymptomatic. More vigorous activity should be introduced gradually over a period of months. (See 'Helping patients advance their exercise program' below.)
Writing the strength training exercise prescription — The benefits of strength training for overall health have been clearly established . As humans age, we undergo a progressive decline in both lean muscle mass and bone density. A well-designed resistance training program can help retard such losses and improve strength, function, and quality of life while reducing the risk for many chronic diseases and premature death. The benefits of strength training are reviewed separately. (See "Strength training for health in adults: Terminology, principles, benefits, and risks".)
A resistance training program is usually done at least two days per week and should include exercises that work all major muscle groups. When lifting weights, it is important to maintain proper technique and to move through a full, functional range of motion. The implementation of strength training programs is discussed separately. (See "Practical guidelines for implementing a strength training program for adults".)
Improving compliance with a basic aerobic exercise program — As with taking prescription medications, getting patients to comply with an aerobic exercise prescription can be challenging. Often, the major barrier is the perceived lack of time due to competing work and family responsibilities. When patients say they cannot find time to exercise, the authors often advise the following:
●Use a workday walking routine – To start the day, park your car further away from your place of work and walk 10 minutes to your worksite. At lunchtime, walk five minutes away from work and five minutes back before eating your lunch. At the end of the day, take that same 10-minute route to walk back to your car. You will now have completed your minimum recommended daily exercise.
●Exercise on weekends – If you simply cannot exercise during the week, do it on the weekends. Taking 75-minute walks on Saturday and on Sunday appears to provide similar health benefits to doing the same total amount of walking during the week . However, it is prudent to build up to the 75-minute walks gradually in order to avoid overuse injuries of the lower extremities and other problems (eg, friction blisters). Perhaps start with 30-minute walks, and on each successive weekend, add five minutes to each walk until you reach 75 minutes.
●Increase workout intensity – You get the same benefit in half the time by performing vigorous as opposed to moderate-intensity exercise. As an example, if you jog for 25 minutes three days each week, you reap benefits comparable to those gained from walking for 30 minutes five days each week.
●Find a partner – Find someone to exercise with or join a group exercise program. This makes exercising more social and fun and increases the likelihood that you will continue. Joining a group of like-minded exercisers (such as a walking group or tennis circle) or a gym can provide necessary encouragement and support. However, such a strategy may be more costly and limit your exercise options. Adopting a dog helps some people exercise more regularly .
●Exercise at home – For some, a home exercise program is just what they need to comply with an exercise prescription. When time is short, being able to use a home exercise bicycle or treadmill without driving to the gym is a great solution. However, quality equipment can be expensive, and oftentimes, the initial enthusiasm for home equipment fades and exercise declines.
●Use a phone app or internet-based fitness program ‒ Another approach to helping patients perform regular aerobic exercise is using a phone app or internet fitness program. Such programs range from yoga to aerobics to resistance exercise circuit training. However, participants should be sure the program selected is appropriate for their fitness level and goals and is well designed with proper instruction about exercise technique.
While smartphone fitness apps continue to grow in popularity, studies of their effectiveness for improving fitness are limited in number and quality, making it difficult to draw meaningful conclusions [28,29]. The following table lists some resources that are available as smartphone apps that may assist in promoting exercise (table 3).
●Join a gym or work with a fitness professional ‒ Joining a local gym or working with a qualified fitness coach can be extremely helpful for some patients who are struggling to adhere to an exercise program. Several professional associations, including the ACSM, offer instruction and proficiency standards and competency certification. A knowledgeable coach can help you create an exercise regimen that best fits your functional status and goals while providing guidance on proper technique to help you avoid injury. A gym or health club can not only provide a safe and inviting place to exercise, it can also provide opportunities for socializing that make exercise more enjoyable, leading to enhanced adherence. Patients with significant cardiovascular disease may find the reassurance of a medically supervised exercise program particularly valuable.
STRATEGIES FOR INCORPORATING EXERCISE INTO THE WORKDAY — For many individuals, finding time to exercise during the workday can be challenging. We advocate a flexible approach and suggest using whatever methods are best suited to individual constraints and most effective for incorporating exercise as part of a daily routine.
Moderate- to vigorous-intensity physical activity, which corresponds to any activity ≥3 metabolic equivalents (METs), has been consistently shown to reduce the health risks associated with chronic diseases and the risk of developing them . Other reports suggest that replacing sedentary time with even brief periods of light physical activity (approximately two minutes per hour) may confer a survival benefit . Accordingly, frequent bouts of light to moderate activity can improve health, especially if the total energy expenditure is comparable to shorter periods of more strenuous physical exertion . Thus, the desk-bound worker who jogs 30 minutes on three days per week may not derive any greater exercise benefits than the worker who does frequent bouts of light to moderate physical activity throughout the day.
Encourage the use of measurement tools ‒ Health professionals can promote physical activity to their patients by encouraging them to use pedometers, accelerometers, and smartphone-based health and wellness applications [5,31,32]. According to one systematic review of randomized trials and observational studies, pedometers are associated with significant decreases in body mass index (BMI) and blood pressure . In another systematic review limited to randomized trials involving adults without chronic illness, the use of smartphone exercise apps or activity trackers was associated with an average increase in daily physical activity equating to 1850 steps per day (95% CI 1247-2457) .
Incorporate more activity into the regular workday ‒ A number of workplace strategies can be used to increase activity throughout the workday, including the following [34-37]:
●Encourage workers to park their car farther from the workplace and walk.
●Use standing or walking desks to reduce sitting time, which is associated with increased morbidity and mortality. (See "The benefits and risks of aerobic exercise", section on 'Physical inactivity and health'.)
●Encourage workers to leave their desk regularly (eg, every 30 to 60 minutes).
●Replace e-mails or phone calls with personal visits.
●Hold standing or walking meetings instead of sitting.
●Use signs to encourage activity .
●Provide access to fitness facilities.
HELPING PATIENTS ADVANCE THEIR EXERCISE PROGRAM
Advancing aerobic exercise
Stages of advancing exercise — Progressive overload is the fundamental principle for advancing exercise. This strategy involves systematically increasing the stress (eg, exercise intensity) placed on the body once it adapts, thereby allowing for continual improvement. Once a regular exercise habit has been established, the patient can advance their aerobic exercise by applying this principle through three basic stages :
●Initial conditioning stage and using heart rate to determine exercise intensity – This stage should begin at an intensity of about 60 percent of the patient’s maximal heart rate, gradually progressing to around 70 percent of the maximal heart rate. For individuals who have not undergone recent exercise testing to determine their "true" maximal heart rate, we recommend using the standing, resting heart rate plus 10 to 25 beats per minute (bpm) to determine initial exercise intensity.
As a general guideline, each 10 bpm increase in heart rate from rest to exercise increases energy expenditure by approximately 1 metabolic equivalent (MET). Thus, if a patient increases their heart rate from 70 bpm at rest to 90 bpm during exercise, they are likely exercising at approximately 3 METs, assuming that the baseline energy expenditure at rest is 1 MET.
This measurement should be supplemented by perceived exertion, which should fall between "fairly light" and "somewhat hard," and symptom assessment (the patient should not experience any adverse symptoms). Exercise is done three days per week, with sessions lasting 12 to 20 minutes. This stage usually extends over a four- to five-week period.
Although the formula "220-age" has been widely used to estimate maximal heart rate, this approach produces considerable variability in healthy people and even greater inaccuracy among individuals with heart disease. The effects of exercise on heart rate may be blunted in patients taking cardiac medications (eg, beta blockers) and in patients with diabetes whose autonomic nervous systems may not function normally. Consequently, this formula may markedly overestimate the maximal heart rate in many middle-aged and older adults. For these reasons, if a maximal heart rate has not been determined through exercise testing, we counsel patients to rely more on exertional symptoms and perceived exertion to regulate their exercise intensity, and we strongly discourage using the 220-age formula.
●Improvement stage – This follows the initial conditioning stage and typically lasts four to five months. This stage involves gradual increases in intensity (up to 70 to 85 percent of the maximal heart rate) and in duration (up to three to five sessions per week). Duration should be increased gradually, until the goal of 30 to 45 minutes per session is achieved, before intensity is raised.
●Maintenance stage – This begins after about six months of training and involves exercising three to five times per week at a target heart rate of 60 to 85 percent of maximum, with a duration of 30 to 45 minutes per session. The goal here is to maintain one's fitness level and functional capacity at the desired level.
A person's risk of injury while exercising is directly related to the gap between their usual level of activity and a new, higher level of activity. The size of this gap refers to one's relative overload, and this should be advanced gradually and in small increments to reduce the likelihood of acute cardiac events and musculoskeletal injury. Older and less fit adults are more prone to exercise-related complications; therefore, increases in their exercise activity should be made even more gradually.
FITT prescriptions for non-sedentary and intermediate exercisers — An exercise prescription template is available from the Exercise is Medicine initiative (EIM exercise Rx template). In addition, sample exercise prescriptions for patients of different fitness levels can be found in the following tables:
●FITT prescription for non-sedentary beginning exerciser (table 4)
●FITT prescription for intermediate exerciser with running (table 5)
●FITT prescription for intermediate exerciser without running (table 6)
Initial and goal exercise intensities for optimal cardiovascular benefit — METs are a common measure of exercise intensity based on comparisons of oxygen consumption at rest and during activity (1 MET = 3.5 mL oxygen/kg body weight per minute). Most middle-aged and older individuals initiate exercise programs at approximately 1 to 3 METs, corresponding to walking at about 2 to 3 miles per hour (3 to 5 km per hour) but fail to increase the intensity of their exercise as their fitness gradually improves. This failure prevents them from achieving the maximal reduction in their risk for cardiovascular disease.
An appropriate initial training goal for sedentary individuals is to achieve an exercise training intensity that elevates them from the most unfit population cohort (bottom 20 percent), which has the poorest health prognosis. Although the threshold for low cardiorespiratory fitness varies by age, this bottom cohort typically has an exercise capacity of ≤5 METs. Our experience suggests that an exercise capacity above 5 METs can be achieved by exercising with an intensity above 3 METs. This corresponds to moderate to vigorous physical activity. Moreover, progressing from an exercise capacity ≤5 METs to >5 METs appears to provide the greatest relative reduction in mortality . With further improvements in exercise capacity, there are continued reductions in the risk of cardiovascular disease but at a less dramatic rate.
To achieve a training intensity ≥3 METs, individuals can walk on a treadmill at 2 miles per hour (3 km per hour) with a 3.5 percent grade or at 3 miles per hour (5 km per hour) on a level (0 percent) grade. The workloads in each case are approximately 3.3 METs.
When exercising on a stationary cycle ergometer, the minimum work rates to achieve an energy expenditure of approximately 3.4 METs are as follows:
●For body weight of 60 kg, 250 kg∙m/min (or 40 Watts)
●For body weight of 80 kg, 350 kg∙m/min (or 57 Watts)
●For body weight of 100 kg, 450 kg∙m/min (or 74 Watts)
●For body weight of 120 kg, 550 kg∙m/min (or 90 Watts)
For outdoor bicycling, the speed corresponding to 3 to 4 METs is approximately 6 miles per hour (10 km per hour).
Cardiorespiratory fitness levels are influenced by age and sex, and little additional survival benefit occurs when levels increase from "good" to "excellent," suggesting there is a plateau in the reduced relative risk for cardiovascular disease that can be achieved through exercise. However, a "good" level of fitness must be achieved to reach this plateau. The following tables provide "good" fitness levels and the aerobic training requirements necessary to achieve them (table 7), and the METs expended during a range of recreational activities (table 8) [40,41]. In creating the reference standards for cardiorespiratory fitness found in the table (expressed as METs), we employed the Fitness Registry and the Importance of Exercise: A National Database (FRIEND) . Age- and sex-adjusted "good" fitness levels were calculated at the 60th percentile.
In our experience, if patients can progress to training intensities that are 60 to 80 percent of their oxygen uptake reserve without adverse signs or symptoms, and without excessive ratings of perceived exertion (ie, ≥15 [hard work] on a scale of 6 to 20), it is likely that they can attain the corresponding age- and sex-adjusted cardioprotective fitness levels that are compatible with increased survival . As an example, "good" fitness for a 65-year-old man is ≥8.7 METs; accordingly, a training level of 5.6 to 7.2 METs, achieved after 3 to 12 months of gradual, progressive increases in exercise intensity, would be a worthwhile goal (again, assuming the patient remains asymptomatic) . This training intensity approximates singles tennis or brisk walking (pace of 4.5 to 5 miles per hour [7 to 8 km per hour]) (table 8) or graded treadmill walking (3 miles per hour [5 km per hour] on a 7.5 percent grade).
Walking at 2 and 3 miles per hour (3 and 5 km per hour) approximates 2 and 3 METs, respectively. At a speed of 2 miles per hour (3 km per hour), each 3.5 percent grade increment adds an additional MET to the energy expenditure. For individuals who can walk at 3 miles per hour (5 km per hour), each 2.5 percent increase in treadmill grade adds an additional MET. Thus, walking at 3 miles per hour on a 7.5 percent grade would approximate 6 METs.
Advancing strength training — Strength exercises provide important health benefits beyond aerobic activity. Once novice trainees develop basic exercise tolerance and strength, programs using barbells provide the most effective means for making further strength gains. The best programs emphasize multijoint exercises (such as the squat, deadlift, and press) that involve all the major muscle groups, working them through a full, functional range of motion. The benefits and implementation of such strength training programs are discussed separately. (See "Strength training for health in adults: Terminology, principles, benefits, and risks" and "Practical guidelines for implementing a strength training program for adults".)
As beginning exercisers become more fit, it is helpful to begin incorporating basic strength and mobility exercises into their workouts. The following figures show how to perform the exercises included in the prescriptions provided above (picture 6 and picture 7). (See 'FITT prescriptions for non-sedentary and intermediate exercisers' above.)
More challenging versions of selected exercises are shown in the following graphics:
●Squat (picture 8)
●Lunge (movie 2)
●Push-up (picture 1)
●Core stability (picture 9)
High-intensity interval training: Which patients are best suited? — High-intensity interval training (HIIT) involves intermittent, usually regularly timed, bouts of high-intensity activity alternating with brief, often timed, periods of low-intensity activity or rest. Numerous studies have compared the effectiveness of moderate-intensity continuous exercise training (MICT) with HIIT for improving aerobic capacity and other measures of cardiovascular function in healthy adults and in patients with coronary artery disease.
In studies of healthy adults, HIIT regimens have been shown to induce greater increases in cardiorespiratory fitness (approximately 0.5 METs) and cardiometabolic health than MICT, especially when the total work performed during training is comparable [43-46]. Thus, for young, healthy, asymptomatic individuals (including military personnel) seeking to improve cardiorespiratory fitness rapidly, HIIT may be a more effective approach. (See "Exercise and fitness in the prevention of atherosclerotic cardiovascular disease", section on 'Type, intensity, and duration of exercise' and "Effects of exercise on lipoproteins and hemostatic factors".)
Among individuals with known coronary artery disease or at high risk for ischemic heart disease, the safety of HIIT remains unclear and should be undertaken, if at all, with great caution, especially in unsupervised, non-medical settings. While HIIT may be an effective approach to exercise for such patients, additional long-term studies assessing safety, compliance, and morbidity and mortality are required before this approach can be widely recommended for such patients [47,48]. Exercise for patients with heart disease is discussed in detail separately. (See "Cardiac rehabilitation: Indications, efficacy, and safety in patients with coronary heart disease" and "Cardiac rehabilitation programs" and "Cardiac rehabilitation in patients with heart failure" and "Cardiac rehabilitation in older adults".)
BASIC NUTRITIONAL GUIDANCE — The contribution of nutrition to health is well established; sound nutrition provides the fuel for all exercise and the building blocks for recovery following exercise . The patient embarking on an exercise program should consume a diet rich in vegetables and fruits, lean forms of protein, and healthy fats while avoiding refined grains (eg, white bread, white rice, pasta, refined and sweetened cereals). The basics of nutrition for health and weight loss are reviewed separately. (See "Healthy diet in adults" and "Obesity in adults: Dietary therapy".)
For clinicians dealing with competitive athletes, detailed nutritional guidance (including information about nutrient timing) is beyond the scope of this topic but is provided in the following reference . Hydration and nutrient timing are important concepts that the clinician advising recreational or competitive athletes should understand. These concepts are discussed briefly below.
Hydration considerations — Water is an essential nutrient for all who exercise. Endurance exercise on average causes one to sweat about 1 L of water per hour while losing 1 g of sodium per hour and burning 80 g of carbohydrate per hour. However, there is wide variation among individuals depending on age, body type, exercise intensity, and environmental conditions (eg, humidity) . Guidance from the National Athletic Trainers Association of the United States about hydration in physically active adults can be found in the following reference .
In general, water needs are best gauged by thirst, especially for light sweaters doing light to moderate exercise. Those performing strenuous exercise or exercising for long durations (>60 minutes) should determine their rehydration needs based on their sweat rate. The sweat rate can be estimated by weighing oneself nude before and after a 60-minute bout of exercise done at a typical intensity and under typical environmental conditions of heat and humidity. The sweat rate is the difference between the pre- and postexercise weight.
Based on the sweat rate estimation, an exerciser should try to replace each 0.5 kg (1.1 lb) of weight lost with 500 mL (17 ounces) of fluid each hour during and after exercise. Of note, this approach underestimates fluid needs for exercise performed at higher intensity or during hotter or more humid conditions than those of the test. Knowing one's sweat rate can help prevent both under- and over-drinking during exercise and help to optimize performance. If a sweat rate cannot be determined, a reasonable strategy is to let thirst guide hydration.
Endurance athletes involved in prolonged bouts of exercise (>60 minutes) who ingest excessive volumes of free water relative to their sweat losses are at risk of developing acute hyponatremia. Strategies for preventing and managing exercise-associated hyponatremia are discussed separately. (See "Exercise-associated hyponatremia".)
Nutrient intake and timing — Training goals are realized more efficiently when appropriate nutritional strategies are implemented before, during, and after training. "Nutrient timing" is the term coined by Drs. John Ivy and Robert Portman to suggest that "when food is consumed" is as important as "what food is consumed" . The three phases of nutrient timing include: during exercise, the period immediately after exercise (ie, recovery), and the interval between exercise sessions (ie, maintenance and growth).
According to the International Society of Sports Nutrition (ISSN) guidelines, the timing of energy intake and the ratio of certain ingested macronutrients (eg, carbohydrate and protein) may enhance recovery and tissue repair, augment muscle protein synthesis, and improve mood following high-volume or intense exercise . Providers who interact with competitive or recreational athletes involved in intense training are directed to the ISSN position stand for detailed reference and guidance . For beginning exercisers and many recreational exercisers who are not participating in high-volume or intense exercise, simply adhering to a sound diet rich in vegetables and fruits, lean forms of protein, and healthy fats is generally sufficient, and concern about the details of nutrient timing is unnecessary.
Salient guidance from the ISSN position statement for general adult exercisers includes the following:
●Endogenous glycogen stores are depleted most by high-volume exercise. These stores are maximized by consuming a diet rich in carbohydrates (8 to 12 g of carbohydrate/kg of body weight per day). For overweight patients, the lean body weight or target body weight can be used to calculate carbohydrate needs. Carbohydrates should take the form of fruits and whole grains; refined grain products (eg, white bread, white rice, pasta, refined and sweetened cereals) should be avoided.
●Extended (>60 minutes) bouts of high-intensity (>70 percent maximum oxygen consumption [VO2 max]) aerobic exercise pose challenges for fuel supply and fluid regulation. The exerciser should consume approximately 30 to 60 g of carbohydrate each hour during intense aerobic exercise that extends beyond 70 minutes. Ideally, this takes the form of a 6 to 8 percent carbohydrate-electrolyte solution (175 to 350 mL, or 6 to 12 fluid ounces) every 10 to 15 minutes.
Particularly when carbohydrate delivery is inadequate, consuming some protein along with the carbohydrate may help increase performance, ameliorate muscle damage, promote euglycemia, and facilitate glycogen resynthesis.
●During a standard strength training workout (eg, three to six sets of 8 to 12 repetitions performing exercises targeting all major muscle groups), consuming adequate carbohydrate has been shown to promote euglycemia and higher glycogen stores. In addition, consuming carbohydrate in combination with protein during and after resistance exercise increases muscle glycogen stores, ameliorates muscle damage, and improves training adaptations. Nutrition for adults participating in resistance training programs is reviewed separately. (See "Practical guidelines for implementing a strength training program for adults", section on 'Nutrition for adult trainees'.)
●Meeting the total daily intake of protein is important for exercising individuals. Consuming high-quality protein within two hours of exercising stimulates muscle protein synthesis and aids recovery. Adults who exercise regularly should try to consume approximately 1.5 g of lean protein/kg of body weight daily. For overweight patients, the lean body weight or target body weight can be used to calculate protein needs.
STRATEGIES TO REDUCE RISK DURING EXERCISE
Contraindications to exercise — Common reasons not to exercise include acute illness or injury. In such circumstances, it is often best to rest and recover before engaging in vigorous exercise, although in many circumstances, patients can perform light activity to maintain some level of fitness. Following significant musculoskeletal injury, a complete functional recovery is important before returning to full sport in order to avoid reinjury. (See "Upper respiratory tract infections: Considerations in adolescent and adult athletes".)
Exacerbations or acute flares of chronic illnesses can restrict exercise. In some cases, alternative forms of exercise that do not exacerbate the acute condition may be used. As an example, a patient experiencing an acute flare of osteoarthritis may be able to swim or perform water aerobics. Societies for several chronic illnesses have established criteria to guide safe participation. Links to topics addressing exercise in patients with specific diseases are provided below.
Guidance for patients with significant chronic disease or other conditions — Many patients with chronic disease can reap significant benefits through regular participation in appropriately designed exercise programs. The role of exercise in adult patients with chronic disease and a range of other conditions is discussed separately.
●Cardiovascular disease (see "Exercise and fitness in the prevention of atherosclerotic cardiovascular disease" and "Cardiac rehabilitation: Indications, efficacy, and safety in patients with coronary heart disease" and "Cardiac rehabilitation programs" and "Cardiac rehabilitation in patients with heart failure" and "Cardiac rehabilitation in older adults")
●Obesity (see "Obesity in adults: Role of physical activity and exercise")
●Aging and exercise (see "Physical activity and exercise in older adults")
●Diabetes mellitus (see "Exercise guidance in adults with diabetes mellitus")
●Hypertension (see "Exercise in the treatment and prevention of hypertension")
●Pulmonary disease (see "Pulmonary rehabilitation")
●Pregnancy and exercise (see "Exercise during pregnancy and the postpartum period")
Common safeguards — The benefits of exercise far outweigh the small associated risks. The benefits and risks associated with exercise are reviewed separately. (See "The benefits and risks of aerobic exercise".)
Many exercise-associated risks can be mitigated by following common sense practices. It is important to encourage patients to "listen" to their body and how it is responding to exercise. The intensity and duration of exercise should be decreased when a person is not feeling well. In general, exercise should be avoided when a patient is severely ill, especially in the presence of fever, productive cough, significant vomiting or diarrhea, or severe pain.
Other important safeguards include exercising with a partner when possible and wearing a medic alert bracelet if a person has a significant medical issue (eg, diabetes, epilepsy, significant allergic reactions) that could affect treatment should something untoward occur.
Emphasize the importance of warm-up and cool-down — There is a sound physiologic basis for recommending calisthenics and a gradual cardiorespiratory warm-up prior to the endurance or stimulus phase of an exercise session. A proper warm-up stretches postural muscles and helps to increase blood flow and the metabolic rate. In addition, it may reduce the potential for ischemic ST-segment depression and ventricular arrhythmias that can be triggered by sudden strenuous exertion . A warm-up may reduce the susceptibility to musculoskeletal injury by increasing connective tissue extensibility and joint mobility.
Our empiric experience suggests that the preferred warm-up for any aerobic activity is that activity performed at a lower intensity (eg, brisk walking before slow jogging over a 5- to 10-minute period). At the conclusion of the warm-up, the heart rate should fall within 10 beats per minute of the lower limit for the endurance or stimulus phase.
For strength training, an appropriate warm-up involves performing the same exercise starting with lower resistance (eg, less weight) and gradually increasing it. For activities that involve complex movements, particularly explosive and unpredictable ones (as with many sports), a warm-up should incorporate the full range of movements to be used, with a gradual increase in intensity. (See "Practical guidelines for implementing a strength training program for adults" and "Anterior cruciate ligament (ACL) injury prevention" and "Throwing injuries of the upper extremity: Treatment, follow-up care, and prevention", section on 'Exercise and throwing programs for treatment and injury prevention'.)
A 5- to 10-minute postexercise cool-down period involving slow jogging, walking, or cycling permits appropriate circulatory adjustments and a more gradual return of the heart rate and blood pressure to near resting values. A proper cool-down enhances venous return, thereby reducing the potential for postexercise hypotension and possible syncope, and combats the potential deleterious effects of the postexercise rise in plasma catecholamines .
Increase exercise intensity gradually — It is always best to begin a new exercise routine at a low intensity, performing fewer repetitions or for a shorter duration. Gradually, exercise volume and intensity may be increased as tolerated. A knowledgeable fitness professional or coach can provide instruction about proper programming and progression of an exercise routine.
Patients with little or no experience exercising in particular should be instructed to begin with small amounts of low-intensity exercise and to build gradually. As an example, a sedentary 55-year-old woman might begin by walking on a level surface at a pace of 1 to 3 miles per hour (ie, 1.5 to 5 km per hour, or approximately 1.7 to 3 metabolic equivalents [METs]). Gradually, over a few weeks, the intensity can be raised, such as by increasing the pace to 3 to 4 miles per hour (ie, 5 to 6.5 km per hour, or approximately 3 to 5 METs). Such gradual increases in intensity may continue for as long as the patient remains asymptomatic. Such an approach helps to minimize the risk of cardiovascular complications and orthopedic injury while enabling individuals to improve their cardiorespiratory fitness.
This approach is particularly important for the least active adults, who represent a "high-risk" cohort (bottom 20 percent in physical activity). If such patients engage in unaccustomed, vigorous-to-near-maximal physical activity, there is a large associated relative risk of an acute cardiovascular event [55,56]. (See "The benefits and risks of aerobic exercise", section on 'Risks of exercise'.)
Emphasize perceived exertion and prescribed training heart rates — As a general guideline, exercise can be monitored by using the rate of perceived exertion (6 to 20 category scale (table 1)) , which, like heart rate, can be used to prescribe and modulate exercise intensity. Exercise rated as 11 ("fairly light") to 13 ("somewhat hard") generally corresponds to the upper limit of recommended exercise intensities during the first six to eight weeks of training. As a patient’s fitness gradually increases, ratings of 13 to 15 ("hard") may be appropriate, provided the exerciser remains asymptomatic. The anaerobic or ventilatory threshold generally occurs within this range. Thus, most physically active persons who remain asymptomatic can rely on perceived exertion, rather than heart rate, to regulate their exercise intensity.
Exercisers who experience exertion-related symptoms (eg, chest pain or pressure, unusual shortness of breath, palpitations) should immediately cease training and seek medical clearance before resuming exercise.
Avoid overtraining — Overtraining syndrome (OTS), most commonly the result of excessive exercise, is an incompletely understood syndrome manifested by systemic symptoms and declining performance. OTS is best avoided by ensuring that the exerciser recovers properly from intense training. Recovery requires adequate hydration and nutrition, sleep and rest, relaxation and emotional support, and active somatic/physical rest. (See "Overtraining syndrome in athletes".)
Educate patients about medical danger signs — A number of observational studies report that competitive and recreational athletes who experience nonfatal or fatal cardiovascular complications during or soon after exercise often had prodromal symptoms (eg, chest pain or pressure, unusual shortness of breath, lightheadedness, palpitations, or a drop in exercise capacity) in the days or weeks before their cardiac event [58-61]. These symptoms were often ignored. Consequently, it is important for clinicians to review with exercising patients, particularly those who are new to exercise or have risk factors for coronary heart disease, symptoms that suggest such disease and the importance of seeking prompt medical evaluation should such symptoms develop. (See "Initial evaluation and management of suspected acute coronary syndrome (myocardial infarction, unstable angina) in the emergency department", section on 'Clinical presentation' and "Approach to the patient with suspected angina pectoris", section on 'History'.)
Account for environmental conditions — Exercising in extreme environmental conditions poses potential health risks. Hot and humid environments increase the risk for exertional heat illness. Adults who have not acclimated to such conditions should exercise with less intensity and for shorter periods and should stop if they develop lightheadedness or any other concerning symptom. Exertional heat illness, including steps for prevention, is reviewed in detail separately. (See "Exertional heat illness in adolescents and adults: Management and prevention" and "Exertional heat illness in adolescents and adults: Epidemiology, thermoregulation, risk factors, and diagnosis".)
Exercising in cold weather poses general risks, such as frostbite, and particular risks for patients with coronary heart disease. A cold-weather face mask or a scarf worn around the mouth may help to reduce such problems [62,63]. It bears emphasis that temperature alone is not the best index of cold stress, and windchill should be accounted for when exercising outdoors. Some general preventative measures for exercising safely outdoors are provided separately. (See "Frostbite: Emergency care and prevention", section on 'Prevention'.)
At high altitude, oxygen availability decreases, leading to increased cardiorespiratory and hemodynamic responses to any given workload. Individuals ascending above 1500 m should refrain from vigorous exercise until they have acclimatized. (See "High-altitude illness: Physiology, risk factors, and general prevention".)
Prophylactic use of cardioprotective medications prior to exercise — Although there are no definitive data indicating that cardioprotective medications prevent acute cardiovascular events due to intense physical exertion, some researchers have suggested that patients at risk may benefit from taking particular medications shortly before strenuous exercise, thereby reducing the potential pathophysiologic consequences of the exercise trigger . We believe that the evidence pertaining to the prophylactic use of cardioprotective medications prior to exercise is too limited to make general recommendations, and any decision to use such strategies requires careful assessment of the individual patient and a detailed discussion of potential risks and benefits .
Short-acting beta blockers and aspirin are the two medications most often considered for prophylaxis against cardiac events during strenuous exercise. Presumably, beta blockers reduce the rate-pressure shear forces and associated cardiac demands during vigorous physical exertion, whereas aspirin likely inhibits epinephrine-induced platelet aggregation [66-70]. Beta blockers appear to show the most promise for cardioprotection during physical stress [66,67]. Studies of aspirin are more limited [68-70].
SURVEILLANCE OF THE ADULT EXERCISER — Once an individual has begun an exercise program, their primary care clinician should have some plan for encouraging their continued participation and monitoring their health. The schedule for such surveillance will vary depending upon patient age, comorbidities, and possibly the intensity of their exercise regimen. These issues are discussed separately. (See "Exercise for adults: Terminology, patient assessment, and medical clearance", section on 'Surveillance of the adult exerciser'.)
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Exercise in adults".)
SUMMARY AND RECOMMENDATIONS
●Terminology and concepts – Regular exercise has wide-ranging health benefits. Exercise types include endurance exercise to improve cardiovascular and respiratory fitness, resistance exercise to improve strength and power, balance and proprioception exercises, mobility exercises, and combinations thereof. The different types and facets of exercise and physical activity are reviewed separately. (See "Exercise for adults: Terminology, patient assessment, and medical clearance", section on 'Terminology and common types of exercise' and "Strength training for health in adults: Terminology, principles, benefits, and risks".)
●Basic exercise prescription – Ideally, an exercise program should include exercises that improve cardiorespiratory fitness, strength, and mobility. A basic exercise prescription can be created using the FITT mnemonic:
•Frequency: Number of days per week (ideally three or more)
•Intensity: Moderate or greater (achieved gradually)
•Time: Number of minutes per session (ideally 30 minutes or longer)
•Type: Aerobic activity of choice (eg, walking, jogging, cycling)
Sample prescriptions for beginning exercisers using this mnemonic are provided (table 2 and table 4). An exercise prescription template from the Exercise is Medicine initiative is available (EIM exercise Rx). (See 'Prescribing an exercise program' above.)
●Improving fitness and compliance with exercise – Strategies for improving compliance and incorporating more exercise into the workday are reviewed in the text and include:
•Using a workday walking routine
•Exercising with a partner
•Using measurement tools (eg, heart rate monitor, pedometer)
•Reducing sitting time by using standing desks and walking meetings
•Training with appropriate, high-quality phone apps or internet exercise programs (table 3) (see 'Improving compliance with a basic aerobic exercise program' above and 'Strategies for incorporating exercise into the workday' above)
●Fitness level to reduce cardiovascular risk – Cardiorespiratory fitness levels are influenced by age, sex, and other factors. Little additional survival benefit occurs when levels increase from "good" to "excellent," suggesting there is a plateau in the reduced relative risk for cardiovascular disease once "good" fitness levels are reached. An initial training intensity goal of ≥3 metabolic equivalents (METs) enables individuals to achieve important fitness goals. The following tables provide "good" fitness levels and the aerobic training requirements necessary to achieve them (table 7), and the METs expended during a range of recreational activities (table 8). (See 'Helping patients advance their exercise program' above.)
●Progressive overload and prescriptions for improving fitness – Progressive overload involves systematically increasing the stress (eg, exercise intensity or duration) placed on the body once it adapts to a previous stress, thereby allowing for continual improvement. Once individuals are exercising consistently and have adapted to a beginner program, more challenging exercise programs are needed if they are to become fitter. Sample prescriptions for such programs using the FITT mnemonic are provided (table 5 and table 6). The exercises included in these prescriptions are found in the following figures (picture 6 and picture 7). More challenging versions of selected exercises are shown in the following graphics:
•Squat (picture 8)
•Lunge (movie 2)
•Push-up (picture 1)
●Nutrition – The patient embarking on an exercise program should consume a diet rich in vegetables, some fruits, lean forms of protein, and healthy fats while avoiding refined grains (eg, white bread, white rice, pasta, refined and sweetened cereals). Nutrition for health and for weight loss is reviewed separately. Some guidance about hydration and nutrition for exercise is provided in the text. (See "Healthy diet in adults" and "Obesity in adults: Dietary therapy" and 'Basic nutritional guidance' above.)
●Reducing risk and avoiding injury – The risks associated with following a well-designed exercise program that accounts for patient age, baseline fitness level, and any comorbidities are low and far exceeded by the wide-ranging health benefits. Following an acute illness or injury, it is often best to rest and recover before resuming exercise. In some cases, alternative forms of exercise that do not exacerbate the acute condition may be used (eg, swimming or water aerobics during osteoarthritis flare). Links to topics addressing exercise in patients with specific diseases are provided in the text, as are strategies for reducing risk during exercise. (See 'Guidance for patients with significant chronic disease or other conditions' above and 'Strategies to reduce risk during exercise' above.)
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