Physical exercise: benefits and harms

Exercise stimulates tissue change and adaptation to physical activity, and rest and recovery allow these changes and adaptations to occur. Rest after exercise is as important as the patient’s desire to perform the exercise. Regular physical activity reduces the incidence of leading causes of death and the likelihood of injury, and improves physical fitness. Certain exercises are also prescribed for the rehabilitation of patients after AMI, major surgery, and musculoskeletal injury. Regardless of the indications, the following two principles must be taken into account when prescribing physical exercises:

• Physical activity goals should be specific to the patient, taking into account motivation, needs, physical capabilities and psychology to ensure maximum interest and participation in achieving the desired result;
• the volume of physical activity must be adequately calculated to achieve the desired effect, it must be sufficient for adaptation to a higher functional state, but not excessive, so as not to cause damage. According to the principle of decreasing repetitions, a lot of physical exercise is not always good; too little or too much is equally bad.

When prescribing physical exercise, it is necessary to specify its intensity (level of load), volume (amount of work per session), frequency (number of sessions) and gradual additional load (either increasing the duration of one or more elements or increasing the actual load). The balance of these elements depends on individual endurance and physiological principles (for example, increasing intensity may require decreasing volume and frequency). Strength, volume and frequency can be increased simultaneously, but up to a certain limit, since human endurance is not unlimited. It is necessary to establish the volume of exercise that is optimally beneficial and consistent with the patient's goals. Fixed and traditional recommendations (e.g. 3 times 10-12 repetitions, running for 30 minutes 3 times a week) are suboptimal and may not meet the individual and specific needs of the patient.

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Stretching and flexibility

Flexibility is important for safe and comfortable physical activity. Specific flexibility exercises involve slow, static stretching of muscle groups without jerking or jumping; these exercises can be performed before or after other forms of exercise or as a stand-alone program, as in yoga or breathing exercises. Although stretching before exercise mentally prepares a person for the exercise, there is no evidence that it reduces the risk of injury. There is no reason to discourage a patient from stretching as a warm-up if he or she enjoys it. General warm-ups (such as low-impact exercise, jogging, calisthenics, or other light exercise that increases core body temperature) are more effective as a warm-up than stretching. Stretching after exercise is preferable because already warm tissues are more easily stretched; this can be useful in strength training to increase range of motion and helps loosen muscles.

Strength exercises

Strength training (resistance training) involves forceful muscle contraction against a load, usually by lifting a free or machine-mounted load. Such exercises increase muscle strength, endurance, and muscle size and improve functional capacity and aerobic performance. Cardiovascular endurance and flexibility are increased simultaneously.

Volume is usually divided into categories: the amount of weight lifted, the number of sets and repetitions. However, such a parameter as the duration of the load, the total duration of lifting and lowering the weight in one set is no less important. The optimal load time is about 60 sec for normal conditions and 90-120 sec for rehabilitation after injuries. To increase strength, the load time is more important than the number of repetitions; the number of repetitions can be changed within the load time due to technique and the duration of the set. When the patient reaches a tension time of at least 60 sec with good technique, the weight (resistance) can be increased so that a tension time of at least 60 sec is acceptable for the next weight level. The number of sets is determined by the intensity of training.

Intensity is a largely subjective measure of the exertion experienced and how close to failure a person has come during a given set. Intensity can be objectively characterized by the weight lifted, expressed as a percentage of the person's 1-repetition maximum (1RM) of a given exercise. This means that for a person whose limit is 100 kg for a single set, 75 kg is 75% RM. Lifting <30-40% RM provides minimal strength gains, although aerobic conditioning can occur with sufficient time under tension and effort. Intensity is limited by the patient's motivation and endurance. For many patients undergoing rehabilitation, discomfort, pain, and lack of training lead them to use less load than they can handle. This is why more sets are recommended to achieve good results. However, prolonged high-intensity training is counterproductive even for trained athletes. Exercising to failure is not necessary to obtain the benefits of strength training. The intensity of training should be changed regularly to ensure mental and physical harmony.

Good technique is essential for safety; avoiding jerking or dropping the weight abruptly, which can cause minor tissue injuries due to sudden muscular effort; controlling breathing, which prevents dizziness (and sometimes fainting), which can occur with the Valsalva maneuver. Patients should exhale as they lift the weight and inhale as they lower it. If the movement is slow, such as lowering the weight in 5 seconds, patients may need to inhale and exhale more than once, but breathing should still be planned so that inhalation occurs before the lifting phase and exhalation occurs at the end. Blood pressure increases during resistance exercise but quickly returns to normal after it is completed. The increase is minimal when breathing technique is correct, no matter how much training the person has had.

Balance exercises

Balance exercises involve finding the center of gravity by practicing unstable positions, such as standing on one leg or using balance or teeter boards. Although specific balance exercises may help some people with poor proprioception, they are often misused to prevent falls in older patients. For most older patients, a controlled flexibility and strength program (such as slow movements using resistance machines or resistance bands) is more effective. Such a program builds joint strength and helps patients maintain stability while standing and walking. If a person has difficulty standing and walking due to poor balance, more challenging balance exercises, such as standing on a teeter board, are more likely to cause injury and are contraindicated in these patients.

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The Importance of Water in Exercise

Adequate hydration is important, particularly if exercise has been prolonged or has taken place in a hot environment. Individuals should be well hydrated before exercise, drink regularly during prolonged exercise, and replace any deficits that develop afterwards. During exercise, approximately 120–240 ml (the volume of one glass) of fluid every 15–20 min is adequate, depending on the heat and level of exercise. However, overhydration, which can cause hyponatremia and cramps, should be avoided. The fluid deficit that follows exercise can be calculated by comparing body weight before and after exercise, replacing the loss one-to-one (e.g. 1 L of fluid for every 1 kg lost). Plain water is adequate in most cases. Electrolyte-containing sports drinks may be preferable. However, fluids with a carbohydrate content >8% may slow gastric emptying, with a concomitant reduction in the rate of fluid absorption. In most cases, it is best to mix plain water with sports drinks in a 1:1 ratio, which will speed up the absorption of glucose and electrolytes. Patients with signs of heat loss or dehydration may require oral or intravenous electrolyte replacement.