special subjects
Overview of Exercise
Introduction
Exercise stimulates tissue change and adaptation (eg, increase in muscle mass and strength, cardiovascular endurance), whereas rest and recovery allow such change and adaptation to occur ( Overview reference ). Recovery from exercise is as important as the exercise stimulus. Regular physical activity reduces the likelihood of medical illness, decreases the incidence of the major causes of death, and improves the overall health and quality of life for patients with most medical conditions. By increasing muscle mass and strength and fostering cardiovascular endurance, exercise improves functional status for sports and activities of daily living and protects against injury. Specific exercise programs are also commonly prescribed to rehabilitate patients after myocardial infarction, major surgery, and musculoskeletal injury. Preoperative exercise regimens are prescribed before many elective surgical procedures to enhance postoperative recovery ( Overview reference ). Regardless of indication, recommendations for exercise should be based on 2 main principles: Goals for activity should be specific to the patient, accounting for motivation, needs, physical ability, and psychology, to maximize the likelihood of patient participation and desired outcome. Activity should be prescribed in a proper dose to achieve a desired effect. An exercise stimulus should be sufficient for the body to adapt to a higher state of function, to maintain a level of function, or to slow the loss of function, but not so great that it causes injury or nonadherence. More exercise or higher-intensity activity is not always better; too little or too much activity may prevent achievement of desired outcomes and effective recovery. The amount of exercise a person requires (as opposed to "can tolerate") to achieve a particular outcome or goal should take into consideration the principle of diminishing returns. A small amount of exercise may yield some results, but perhaps not the full or intended results. More activity would be required to generate desired results, but at some point, the harm outweighs the benefit. For example, 25% more work may yield 5% better results but places more strain on the joints and the person's mental and physical capacities, and the additional work may require more recovery time. Therefore, exercise programs should be designed economically, with gradually increasing overall demands (eg, how much or how hard to exercise) while monitoring results (gains and recovery). A prescription for exercise should specify intensity (level of exertion), volume (amount of activity in a session), frequency (number of exercise sessions), and progressive overload (either the amount of increase in one or more of these elements per workout or the actual load). The balance of these elements depends on individual tolerance and physiologic principles (ie, as intensity increases, volume and frequency may need to decrease, whereas as volume increases, intensity may need to decrease). Intensity, volume, and frequency can be increased concurrently, but increases are limited because human tolerance to strain is finite. The objective is to discover the appropriate amount of exercise for optimal benefit in the context of the patient’s goals, health status, and current fitness level. Fixed and traditional generic recommendations (eg, 3 sets of 10 to 12 repetitions, running 30 minutes 3 times/week) may be suboptimal because they do not address a person’s specific requirements or capability (ie, people with marked deconditioning require a different program than people with the ability to train at higher intensity levels). Variation in the regimen helps avoid over-adaptation (staleness) to the same stimulus as well as minor injuries due to repetitive actions. Achieving long-term adherence is important and challenging. People differ greatly in their motivation and ability to sustain what they may perceive as arduous activity. To improve adherence, training programs typically start at low intensity levels and gradually increase to the target level. Some people require individually supervised exercise (eg, by a personal trainer), others benefit from the support of organized group activity (eg, an exercise class, group bike ride), and some are able to engage in long-term solitary exercise. For people to sustain motivation over the long term, exercise prescriptions should take into account their needs (eg, leg strengthening exercises for someone wheelchair dependent), what is actually required for them to achieve a particular goal (ie, how realistic the goal is), and preferences (eg, the type of fitness program). Exercise programs should encompass multiple dimensions of fitness, including Stretching and flexibility Aerobic capacity (cardiovascular endurance) Strength (including muscular endurance and muscle size or structure) Balance Activity Activity 125-lb (57-kilogram) person 125-lb (57-kilogram) person 175-lb (80-kilogram) person 175-lb (80-kilogram) person Aerobics 283 396 Biking 453 635 Cross-country skiing 453 635 Downhill skiing 340 476 Golf Riding cart 198 277 Carrying clubs 311 436 Hiking 340 476 Ice skating 396 555 In-line skating 283 396 Running 8-minute mile 708 992 12-minute mile 453 635 Softball 283 396 Swimming 453 635 Swing dancing 226 317 Tae kwon do 283 396 Tennis (singles) 453 635 Walking 198 277 Weight lifting 170 238 Yoga 226 317 *Average calories expended in 1 hour. 