Principles of Exercise Prescription
The ideal exercise prescription addresses cardiorespiratory, muscular fitness, flexibility, and body composition. A dose-response relationship exists between physical activity and health outcomes in domains, such as all-cause mortality, cardiorespiratory health, metabolic health, weight loss, bone health, cancer risk reduction, and sleep (1). Exercise prescriptions should be individualized with four main, adjustable components: frequency, intensity, time, and type (FITT).
Exercise Prescription for Cardiorespiratory Fitness
For cardiorespiratory fitness, the 2018 Physical Activity Guidelines suggest at least 150 min a week for moderate-intensity (3 to 5.9 metabolic equivalents [METs]), or at least 75 min·wk−1 for vigorous-intensity (≥6 METs) aerobic physical activity over 3 to 5 d·wk−1 (1). The Talk Test is a simple way to measure relative intensity where an individual can talk but not sing during moderate-intensity activity and cannot say more than a few words without pausing for breath with vigorous-intensity activity (2). Gradual adjustments to FITT can minimize shortness of breath, muscle soreness, injury, and risk of overtraining (3). Higher intensity exercise, when appropriate, can provide greater health and fitness benefits (4). Progression of 5 to 10 min every 1 to 2 wk over 4 to 6 wk is reasonable for adults. Interval training that alternates between levels of intensity can yield similar gains compared with traditional endurance training but with less time commitment (5). Aiming for total energy expenditure of ≥500 to 1000 METs·min−1·wk−1 is associated with lower rates of cardiovascular mortality (2). In terms of time, the guidance for adults no longer requires physical activity to occur in bouts of at least 10 min (1). Exercise types include (A) endurance activity with minimal skill or physical fitness, (B) vigorous intensity requiring minimal skill, (C) endurance activity requiring skill, or (D) recreational sport.
Exercise Prescription for Musculoskeletal Fitness
Musculoskeletal fitness uses resistance training that varies in intensity based on strength, hypertrophy, power, and local muscular endurance goals. The 2018 Physical Activity Guidelines suggest resistance training of all major muscle groups with at least one set of 8 to 12 repetitions and at least 2 d·wk−1 (1). Beginners start at 60% to 70% of 1-repetition maximum (RM) for 8 to 12 repetitions to improve fitness while experienced exercisers can have wider ranges based on goals (2). A higher frequency of training for a muscle group can lead to increased muscle hypertrophy when it increases total weekly training volume (6,7). Intensity and repetitions for experienced exercisers depends on the goal of strength (>60% 1-RM), hypertrophy (80% to 100% 1-RM), power (up to 60% 1-RM for 3 to 6 repetitions), or lean muscle endurance (≥15 repetitions) (2). Incorporation of progressive overload is used to achieve increases in muscular fitness as the exercise program advances. Examples include increasing loads by 5% each subsequent session or varying the sets per week. Resistance exercise programs should prioritize large before small muscle groups and multiple-joint before single-joint exercises. Pairing opposing muscle groups in a routine can help avoid imbalances (8). In terms of rest intervals, individuals seeking time efficiency can rest 60 to 120 s in between sets (9).
Incorporating flexibility training when muscles are warm can increase range of motion. At least 2 to 3 d·wk−1 of stretching and 60 to 90 s per joint total is recommended (2,8). Static, dynamic, ballistic, and proprioceptive neuromuscular facilitation approaches to flexibility exercises are each effective for increasing range of motion. Improvement in range of motion can be expected after 3 to 4 wk of stretching two to three times per week (2). Dynamic stretches of at least 30 s, which mimic the intended exercise, are recommended prior to exercise (2). Regular flexibility exercises can improve postural stability and balance which is particularly relevant for aging adults to reduce risk of fall.
Screening and Referrals before Exercise
Preparticipation screening is used to identify individuals who are at risk for adverse exercise-related cardiovascular events and musculoskeletal injury. Traditional cardiovascular risk factors include a history of diabetes, hypertension, hyperlipidemia, age, sex, obesity, and premature family history of cardiovascular disease (2). The United States Preventive Services Task Force advises against routine use of resting or exercise electrocardiogram to screen asymptomatic individuals at low risk (atherosclerotic cardiovascular disease<10%) (10). Acute coronary syndrome can be triggered by unaccustomed vigorous physical activity. This event risk decreases with gradual increases in regular exercise volume (8). Individuals who have sedentary lifestyles ought to start with light to moderate-intensity exercise. Tools, such as the ACSM preparticipation algorithm or 2020 Physical Activity Readiness Questionnaire, may help highlight those individuals who need further medical evaluation prior to increased physical activity (2).
Overcoming the Inertia of Sedentary Behavior
Strategies to enhance confidence can help overcome sedentary behavior. They require setting realistic goals that are specific, measurable, attainable, relevant, and time-based. Maintaining daily progress, using positive reinforcement, and finding social support are ways to overcome exercise barriers. Motivational interviewing can increase motivation for change and ensure adherence to exercise (2).
The authors declare no conflict of interest and do not have any financial disclosures.
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