Therapeutic Exercise

Maintaining cardiovascular fitness and regular physical activity are important components of a healthy lifestyle, which provide a number of health-related benefits. Proper exercise prescription is crucial, and it entails an understanding of exercise physiology, metabolic energy systems, and musculoskeletal and cardiorespiratory physiologies, with particular consideration for special populations.

Energy Systems (eSlide 15.1)

The energy needed to fuel biologic processes is produced from the breakdown of adenosine triphosphate (ATP). There are limited stores of ATP in skeletal muscles, which can provide an immediate burst of high-intensity exercise for 5–10 seconds. After this, subsequent production of ATP may occur via three metabolic pathways: the ATP–creatine phosphate system, rapid glycolysis, and aerobic oxidation.

Adenosine Triphosphate–Creatine Phosphate System

The ATP–creatine phosphate system transfers a high-energy phosphate from creatine phosphate to adenosine diphosphate (ADP) to regenerate ATP.This anaerobic system can provide ATP for approximately 30 seconds for activities such as sprinting and weightlifting.

Rapid Glycolysis (Lactic Acid System)

Glycolysis uses carbohydrates, primarily muscle glycogen, as a fuel source. In the absence of oxygen, the anaerobic pathway is utilized, producing lactic acid. Anaerobic glycolysis begins and dominates for approximately 1.5–2 minutes to provide fuel for high-energy burst activities such as middle-distance sprints (400-, 600-, and 800-m runs) or weightlifting. Lactic acid accumulation limits physical activity as it leads to fatigue and diminished performance. However, under aerobic conditions, lactate serves as a metabolic intermediate, which is converted into pyruvic acid and subsequently into energy (ATP), or it can be used to produce glucose (hepatic gluconeogenesis) via the Cori cycle.

Aerobic Oxidation System

The final metabolic pathway for ATP production involves the Krebs cycle and electron transport chain. The mitochondrial aerobic oxidation system uses carbohydrates, fats, and small amounts of protein to produce ATP through oxidative phosphorylation, which provides energy after 2–3 minutes of activity and continues thereafter until limited by the amount of available fuel and oxygen. Short, intense activities rely on anaerobic systems, whereas longer and low-intensity activities use the aerobic system. Carbohydrates are primarily used at the onset of exercise, and there is a gradual shift to fat metabolism during prolonged exercise (lasting longer than 30 minutes).

Cardiovascular Exercise

Cardiorespiratory Physiology

The cardiorespiratory system delivers oxygen and nutrients to the cells and removes metabolic waste products. The normal resting heart rate (HR) is 60–80 beats/min. The HR increases linearly in proportion to the relative workload and is affected by age, body position, fitness, type of activity, presence of heart disease, medications, blood volume, and certain environmental factors, such as temperature and humidity. The maximal HR (HR _max ) decreases with age and can be estimated with the following formula: HR _max = 220 − age. Stroke volume (SV) is the amount of blood ejected from the left ventricle in a single heart beat and is equal to the difference between the left ventricular end-diastolic volume and left ventricular end-systolic volume. At rest, SV is 60–100 mL/beat and is generally higher in males than in females. During exercise, SV increases in a curvilinear relationship with the work rate but plateaus at approximately 50% of aerobic capacity because of reduced left ventricular filling time during diastole. Cardiac output (Q) is the volume of blood pumped by the heart each minute. Age, posture, body size, presence of cardiac disease, and physical conditioning can all affect the Q. During dynamic exercise, Q increases because of an increase in both the SV and HR. However, at 40%–50% of the maximal oxygen consumption ( V˙
V ˙
o _2max ), the increase is mainly because of an increase in HR. Blood pressure is the driving force behind blood flow. Systolic blood pressure (SBP) increases linearly with increasing work intensity, whereas diastolic blood pressure (DBP) remains unchanged or only slightly increased, regardless of body position. Failure of SBP to increase, decreased SBP with increasing work rate, or a significant increase in DBP are all abnormal responses to exercise. Arm work causes greater increases in HR, SBP, and DBP than leg work because a higher percentage of the available muscle mass is recruited to perform arm work.

Pulmonary ventilation ( V˙
V ˙
e) is the volume of air exchanged per minute. Increases in V˙
V ˙
e are generally directly proportional to an increase in oxygen consumption ( V˙
V ˙
o ₂ ) and carbon dioxide production ( V˙
V ˙
co ₂ ) until the anaerobic threshold is reached, signifying the onset of metabolic acidosis. V˙
V ˙
o _2max is widely used as a measure of cardiopulmonary fitness; it is defined as the highest rate of oxygen transport or use (i.e., consumption) that can be achieved at maximal physical exertion. Metabolic equivalents are used to quantify levels of energy expenditure and are considered the best index of physical work capacity. The physiologic effects of cardiovascular activity and other benefits of regular exercise training are summarized in eSlides 15.2 and 15.3 .

These changes are lost after 4–8 weeks of detraining. Overtraining fatigue syndrome can occur and is characterized by premature fatigability, emotional and mood changes, lack of motivation, infections, and overuse injuries.

Exercise Prescriptions

Components of an exercise prescription include the mode, intensity, frequency, duration, and progression of an exercise. The prescription should be developed with careful consideration of the individual’s health status, medications, risk factor profile, behavioral characteristics, personal goals, and exercise preferences. The recommendations for cardiorespiratory endurance training by the American College of Sports Medicine (ACSM) are summarized in eSlide 15.4 .

Medical Clearance and Preexercise Evaluation

Exercise training may not be appropriate for everyone and is contraindicated in the settings of acute cardiac disease or other conditions in which exercise may exacerbate the disease. The preexercise screening and need for physician evaluation depend on the risk for the individual and the intensity of the planned physical activity. Exercise stress tests are warranted in patients with known or suspected coronary or valvular heart disease, documented cardiac rhythm disorders, multiple cardiac risk factors, or pulmonary limitations; healthy individuals in high-risk occupations, such as pilots, firefighters, law enforcement officers, and mass transit operators; and men older than 40 years and women older than 50 years who are sedentary and plan to start a vigorous exercise program.

Muscle Physiology (eSlide 15.5)

Each skeletal muscle is made of many muscle fibers. The fibers contain hundreds to thousands of myofibrils that are suspended in a sarcoplasmic matrix containing potassium, magnesium, phosphate, enzymes, mitochondria, and the sarcoplasmic reticulum, which are essential for muscle contraction.

Physiology of Muscle Contraction

Sliding Filament Mechanism (eSlide 15.6)

The sliding filament mechanism of muscle contraction is shown in eSlide 15.6 . At the molecular level, as calcium is released from the sarcoplasmic reticulum, it binds to troponin C, uncovering active actin sites hidden by the troponin–tropomyosin complex, along with the release of ATP at the myosin heads, resulting in muscle contraction.

Muscle Fiber Types (eSlide 15.7)

Muscle fibers can be characterized on the basis of their speed of contraction or twitch. Type 1 (slow oxidative) fibers are best suited for endurance activities that require aerobic metabolism. Type 2 (fast twitch) fibers are most active during activities that require strength and speed. They are further categorized into type 2A (fast oxidative–glycolytic) and type 2B (fast glycolytic).

Muscle Fiber Orientation

Muscle fibers are arranged parallel to the length of the muscle. This produces a greater range of movement (ROM) than similar-sized muscles with a pennate arrangement of fibers.

Types of Muscle Contraction and Factors Affecting Muscle Strength and Performance (eSlide 15.7)

Isometric contractions cause no change in muscle length and no joint or limb motion. Isotonic contractions result in muscle length changes, producing limb motion. Concentric contractions result in muscle shortening, whereas eccentric contractions produce muscle lengthening. In general, more fast-twitch fibers are recruited during eccentric contractions than during concentric contractions. Isokinetic contractions are performed at a constant velocity.

Length–Tension Relationship

The maximum force of contraction occurs when a muscle is at its normal resting muscle length, which corresponds to about the midrange of joint motion or slightly longer; it is the length at which tension just begins to exceed zero. If a muscle is stretched beyond its resting length before contraction, resting tension develops and active tension (the increase in tension during contraction) decreases. The most efficient work occurs at approximately 30% of the maximum velocity of muscle contraction.

Torque–Velocity Relationship

A muscle generates the greatest amount of force during fast eccentric (lengthening) contractions, followed by isometric contractions and slow concentric contractions. The least force is produced during fast concentric (shortening) contractions.

Effects of Resistance Training (eSlide 15.8)

The s pecific a daptations to i mposed d emands (SAID) principle states that a muscle adapts to the specific demands imposed on it, enabling it to handle a greater load. Observed strength gains within the first few weeks of a weightlifting program are mostly because of neuromuscular adaptations. Muscle hypertrophy is the enlargement of total muscle mass and cross-sectional area. It occurs after 6–7 weeks of resistance training and is more prominent in fast-twitch muscles than in slow-twitch muscles.

Exercise Prescription

Advancements in a training program can include increasing the amount of weight lifted (progressive resistive exercise), number of repetitions, or rate of exercise. One repetition maximum (RM) is the maximum weight that can be lifted at a time and is commonly used as a measure of one’s current strength and a basis for establishing strength training programs and goals. Exercising to the point of fatigue can be critical for developing muscle strength. Using higher weights to the point of fatigue is more effective; however, low weight–high repetitions can be more appropriate, especially when training after an injury.

Progressive Resistance Exercise Protocols

Examples of progressive resistance exercise protocols are as follows:

1.

The DeLorme (progressive resistive) method: three sets of 10 repetitions. The weight for the first set is 50% of the 10-RM, the second set is 75%, and the third set is 100%.
2.

The Oxford (regressive resistive) technique: 10 repetitions at 100% of the 10-RM, followed by 10 repetitions at 75% and 10 repetitions at 50%.
3.

Daily adjusted progressive resistance exercise (DAPRE) method: four sets of exercise per muscle group. The first set in DAPRE involves 10 repetitions at 50% of the individual’s 6-RM, second set involves six repetitions at 75%, and the third set involves as many repetitions as possible at the individual’s 6-RM. The number of repetitions performed in the third set determines the resistance for the fourth set.

Plyometrics

Plyometric exercises are brief explosive maneuvers that consist of an eccentric muscle contraction followed immediately by a concentric contraction. This more advanced type of stretch–shortening cycle is analogous to a spring coiling and uncoiling. It involves a more neural feedback that influences muscle length and tension and is primarily used in athletic training.

Proprioception

Proprioceptive organs, including muscles (particularly intrafusal spindle fibers), skin, ligaments, and joint capsules, generate afferent information crucial to the effective and safe performance of motor tasks. Impaired proprioception increases the risk for injury and may influence progressive joint deterioration associated with osteoarthritis, rheumatoid arthritis, and Charcot disease.

The tilt or wobble board is commonly used as part of proprioceptive training after ankle ligamentous injuries.

Neurofacilitation Techniques

Neurofacilitation techniques may be applied in patients with central nervous system (CNS) dysfunction. The following are commonly used in a more eclectic manner to provide compensatory techniques during the course of recovery, with the goal of improving function.

Proprioceptive Neuromuscular Facilitation

Proprioceptive neuromuscular facilitation (PNF) uses spiral or diagonal movement patterns to indirectly facilitate movement, with the therapist providing maximal resistance to the stronger motor components, thereby facilitating the weaker components of the patterns. PNF techniques are best used in patients with hypotonia of supraspinal origin and are not recommended for spastic patients because they may increase tone.

Brunnstrom Techniques

These techniques use resistance and primitive postural reactions to facilitate gross synergistic movement patterns and increase muscle tone during early recovery from CNS injury. They are useful in patients with flaccid hemiplegia.

Bobath Techniques

These are neurodevelopmental techniques that use reflex inhibitory movement patterns to decrease hypertonia. These inhibitory patterns are generally antagonistic to the primitive synergistic patterns performed without resistance. Neurodevelopmental techniques also incorporate advanced postural reactions to stimulate recovery.

Flexibility (eSlide 15.9)

Flexibility is the ROM present in a joint or group of joints that allows normal and unimpaired function. Although it varies innately with gender (females have more flexibility than males) and ethnicity, improved flexibility can be acquired through stretch training. Flexibility is greatest during infancy and early childhood and decreases with age. It is an important component of therapeutic exercise that prevents injury, reduces muscle soreness, enhances skill and performance, and provides muscle relaxation. Excessive flexibility may be a detriment to performance if it produces instability. In general, stiff structures benefit from stretching, whereas hypermobile structures require stabilization rather than additional mobilization.

Determinants of Flexibility

The muscle–tendon unit is the primary target of flexibility training, given that muscle has the largest capacity for lengthening. Dynamic factors include neuromuscular variables, such as the muscle tension feedback control system composed of intrafusal fibers (muscle spindles) and Golgi tendon organs (musculotendinous unit) that act via their segmental input at the spinal cord, as well as external factors, such as pain associated with an injury. Flexibility is generally assessed in terms of limb joint ROM with the use of a goniometer or similar device. The Schober test and fingertip-to-floor measurements can be used to assess trunk flexibility.

Methods of Stretching

Ballistic

This method uses the repetitive rapid application of force in a bouncing or jerking maneuver. Ballistic stretching is not recommended as it increases the risk for injury because of muscle guarding caused by overstretching.

Passive

This method is performed by a partner or therapist who applies a stretch to a relaxed joint or extremity. It requires excellent communication and slow and sensitive application of force.

Static

This method involves the application of a steady force for a period of 15–60 seconds. It is the easiest and safest type of stretching and is particularly helpful for any form of therapeutic or recreational exercise, including athletic activity. It is also associated with decreased muscle soreness after exercise.

Neuromuscular Facilitation

This is most frequently used in hold–relax and contract–relax techniques, wherein isometric or concentric contraction of the musculotendinous unit follows a passive or static stretch. The prestretch contraction facilitates relaxation and flexibility via the muscle length–tension thermostat discussed previously in this chapter.

ACSM’s Guidelines for Exercise Prescriptions for Strength Training and Musculoskeletal Flexibility (eSlide 15.10)

Please refer to eSlide 15.10 for the recommended guidelines.

Exercise for Special Populations

Physical Inactivity and Obesity

Physical inactivity is associated with increased fat and visceral adipose tissue accumulation, which increases the risk for diabetes, heart disease, and stroke. Body mass index (BMI) greater than 23 kg/m ² and 25 kg/m ² in middle-aged women and men, respectively, increases the risk for coronary heart disease. Treatment of obesity should be tailored according to its severity and the presence of comorbidities.

Exercise for Fat Reduction (see eSlide 15.15)

Successful weight loss requires a combination of diet and exercise. Caloric restriction should accompany moderate-intensity, land-based activity of 30–60 minutes per day at least twice a week, with a regimen aiming to reach 60%–85% of resting HR during exercise and activating all major muscle groups (in the chest, abdomen, back, and all extremities). Medications may be considered as an adjunct among people with BMI greater than 30 kg/m ² or those with obesity-related disorders.

Pregnancy (eSlide 15.11)

The acute physiologic responses to exercise are generally increased during pregnancy.

Pregnant women can continue to do aerobic exercise at mild-to-moderate intensity (30 minutes at least three times a week) and undergo strength-training program that incorporates all major muscle groups and permits multiple repetitions. However, pregnant women should avoid exercising in the supine position after the first trimester (because of decreased Q in that position), isometric exercises and Valsalva maneuvers, prolonged periods of motionless standing, and recreational activities with a high risk for falling or abdominal trauma. Adequate hydration and nutrition (e.g., an additional 300 kcal/day) should be ensured, and exercise should be continued only to the point of fatigue and not exhaustion. Exercise is contraindicated in the presence of vaginal bleeding, dyspnea before exertion, dizziness, headache, chest pain, muscle weakness, calf pain or swelling, preterm labor, decreased fetal movement, and amniotic fluid leakage. If calf pain and swelling are present, thrombophlebitis should be ruled out. Exercise may be resumed 4–6 weeks postpartum.

Children (eSlide 15.12)

Healthy children should be encouraged to engage in physical activity on a regular basis, especially in light of the increasing rates of childhood obesity and comorbidities. However, given their immature anatomy and physiology, the design of any exercise program should consider their increased risk for overuse injuries, the possibility of damage to epiphyseal growth plates, and their tendency toward hypothermia or hyperthermia (because of less efficient thermoregulation).

Activity for Older Adults (eSlide 15.13)

The loss of strength and stamina, attributed to aging, is partly caused by reduced physical activity. Loss of muscle mass (known as sarcopenia) results from disuse of the muscle, with an associated decrease in growth factors and functional motor units. V˙
V ˙
o _2max decreases by approximately 5%–15%, and HR _max decreases by 6–10 beats/min each decade, starting at 25–30 years of age. However, the benefits of exercise include lowering the risk for cardiovascular morbidity and being associated with higher functional health and better cognitive function. Exercise or activity modifications for medical comorbidities and limitations are important. Aquatic (pool) therapy is particularly helpful for individuals with both peripheral joint and spinal facet arthropathies. Mind–body integrative approaches, such as yoga, Tai Chi, and Pilates, are safe and useful alternatives.

Diabetes Mellitus (eSlide 15.14)

The response to exercise in patients with type 1 diabetes mellitus depends on a variety of factors, including the adequacy of glucose control by exogenous insulin. Serum glucose concentrations in the general range of 200–400 mg/dL require medical supervision during exercise, and exercise is contraindicated for those with fasting glucose serum values greater than 400 mg/dL. Exercise-induced hypoglycemia is the most common problem during exercise, and it may last for up to 4–6 hours postexercise. Aerobic and resistance training guidelines for patients with type 1 diabetes mellitus are similar to those for the general population. However, additional precautionary measures include the following: frequent blood glucose monitoring, decreasing the insulin dose (e.g., by 1-2 units, as prescribed by the physician) or increasing carbohydrate intake (e.g., 10-15 g carbohydrate per 30 minutes of exercise) before an exercise session, avoiding exercise during times of peak insulin levels, eating carbohydrate snacks before or during prolonged exercise sessions, being able to detect the signs and symptoms of hypoglycemia and hyperglycemia, exercising with a partner, using proper footwear, avoiding exercise in excessively hot environments, avoiding jarring activities (if advanced retinopathy is present), and being aware of medications that can mask hypoglycemic or angina symptoms (e.g., beta-blockers).

Hypertension (eSlide 15.15)

Aerobic or endurance exercise training may be part of the initial nonpharmacologic treatment strategy, along with lifestyle modification, for individuals with mild-to-moderate essential hypertension. The recommended mode, frequency, duration, and intensity of exercise for patients with hypertension are generally similar to those for healthy individuals but with lower intensities (e.g., 40%-70% of V˙
V ˙
o _2max ). Resistance training may be incorporated but should not be the primary form of exercise. Exercise should be avoided if resting SBP is greater than 200 mm Hg and/or DBP is greater than 110 mm Hg. When exercising, the SBP should be maintained at less than 220 mm Hg and/or the DBP at less than 105 mm Hg.

Peripheral Vascular Disease (eSlide 15.15)

Patients with peripheral vascular disease (PVD) experience ischemic leg pain (claudication) during physical activity because of a mismatch between active muscle oxygen supply and demand. Pain is typically described as a burning, searing, aching, tightness, or cramping sensation in the calf, but it may originate from the buttock and radiate down the leg. The pain disappears with rest, but it may persist in severe cases. Treatment for severe PVD includes blood thinners, angioplasty, or bypass grafting. Weight-bearing exercise is preferred if tolerated, but non–weight-bearing exercise is a suitable alternative, with intensity limited by pain.

Myofascial Pain Syndrome and Fibromyalgia (eSlide 15.15)

Patients with myofascial pain syndrome or fibromyalgia will benefit from initial low-intensity aerobic exercise combined with stretching. On the basis of the physiologic response and maintenance of functional skills, the intensity of exercise is increased.

Organ Transplantation (eSlide 15.15)

Patients with an organ transplant are deconditioned and weak postoperatively, which can be partly attributed to their immunosuppressive medications. After heart transplantation, sinus node denervation is present, which makes the HR response an unreliable measure of exercise intensity. In these patients, the Borg Rate of Perceived Exertion Scale is preferred. Rehabilitation after solid organ transplantation appears highly beneficial. It also aids in psychological and physical recovery, thereby improving the quality of life.

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Tags: Braddom’s Rehabilitation Care: A Clinical Handbook

Apr 6, 2024 | Posted by drzezo in PHYSICAL MEDICINE & REHABILITATION | Comments Off

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