Workouts promote physical fitness which comprises: cardiovascular endurance, muscular strength, muscular endurance, flexibility, and agility. This article will discuss the physiological changes that occur during physical exercise and workouts.
According to 2008 physical activity guidelines for Americans, 150 moderate to vigorous exercises per week for adults help prevent a wide range of cardiovascular diseases - stroke, diabetes, hypertension, depression, and cancer (lung and endometrial cancer) as well as reduce risks of early death, weight gain, hip fracture, and improvement of sleep quality.
During exercise, the oxygen and substrate requirements in the skeletal muscles increase as well as the elimination of metabolic wastes and carbon dioxide. To satiate these demands, chemical, thermal and mechanical stimuli alter the metabolic, cardiovascular, and ventilatory functions.
When the human body is challenged with tasks such as physical exercise and workouts, it undergoes physiological modifications to cope with the stress. The degree of the adjustments is associated with the intensity, duration, and frequency of the exercise, the force used in training, and the body's level of fitness before the training.
The response of the body to physical exercise occurs in the musculoskeletal, nervous, cardiovascular, respiratory, endocrine, and immune systems.
Cardiovascular System
The cardiovascular system is composed of the heart, blood, and blood vessels. The design responds to exercises in an integrated way that allows it to satisfy the metabolic requirement of the working muscles and preserve the needed homeostasis for a normal body operation. The response is proportional to the oxygen demands of the skeletal muscles which increase as the rate of physical exercise grows.
Physical exercise affects the constituents of the cardiovascular system differently. Energy demand during exercise is greater than those at rest. This prompts an increase in oxygen and nutrient delivery to the active cells and tissues.
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| Physical exercise affects the constituents of the cardiovascular system differently. Energy demand during exercise is greater than those at rest. This prompts an increase in oxygen and nutrient delivery to the active cells and tissues. |
The cardiovascular system responds to high demands by increasing blood flow to the working muscles while at the same time maintaining the arterial pressure within homeostatic parameters.
Cardiac Response
During exercise, the whole body's oxygen consumption increases according to the depth of the exercise. The cardiac output and oxygen extraction also increase to accommodate the elevated blood and oxygen needs of the working tissues.
The cardiac response to physical exercise involves both increased heart rate and stroke volume which is directly related to neural and hormonal mechanisms, alternation in venous blood flow which increases ventricular preload, and peripheral vasodilation which decreases afterload.
Cardiac Output
Cardiac output is the measure of blood leaving the left ventricles of the heart per minute. The volume increases rapidly during moderate exercise. The rate of increase is dependent on the intenseness of the exercise which determines the oxygen demand of the workout. The steady state of cardiac output is maintained by the increase in heart rate and stroke volume.
Heart Rate
Heart rate defines the number the heart beats per minute. The increase or decrease is influenced by hormonal and neural factors.
When an exercise is initiated, parallel activation of the motor cortex and cardiovascular control center of the medulla occurs. The muscles are also stimulated to contract. The mechanoreceptors and chemoreceptors stimulated by muscle contraction promote the continued rise in heart rate which is vital in enabling increased cardiac output.
Stroke Volume
This is the volume of blood pumped per heartbeat. The increase in stroke volume is a function of changes in preload, afterload, and intrinsic cardiac contractility. More venous blood returning to the heart increases preload in the ventricles resulting in more forceful ventricular contraction and higher stroke volume. The afterload decreases due to peripheral resistance which helps to produce a greater stroke volume.
Blood Pressure
Mean arterial pressure increases with dynamic exercise as a result of increased systolic blood pressure. The diastolic blood pressure remains near resting levels.
Blood pressure response to exercise is both age and gender-related. Young men (20-29 years) have lower blood pressure during maximal exercise compared to older men (70-79 years) with higher blood pressure. Older women (79yrs) experience blood pressure elevation to 203mm/Hg. The blood pressure of women in their 20s increases to 90mm/Hg from 74mm/Hg.
It is important to note that both low and exaggerated blood pressure during heightened exercise is associated with cardiovascular diseases which cause mortality.
Respiratory System
The challenge of exercise increases pulmonary ventilation almost immediately through the stimulation of respiratory centers in the brain stem and feedback from the proprioceptors in the muscles and joints of the active limbs.
At a higher exercise level, an increase in carbon dioxide production, hydrogen ions, and body and blood temperature stimulates a further increase in pulmonary ventilation.
The increment in pulmonary ventilation is linked to increases in tidal volume and the respiratory rate which matches the high oxygen intake and carbon dioxide output.
During strenuous exercise, breathing capacity does not reach its maximum level, and therefore not responsible for the limitation in oxygen delivery to the muscles during intensive exercise. Hemoglobin is fully saturated with oxygen in people having normal functioning of the respiratory system.
Endocrine System
The hormonal system plays a fundamental role in the maintenance of homeostasis at rest and during exercise. The system controls the release of hormones from specialized glands which exert their influence on targeted cells and organs.
During exercise, some hormones (catecholamines) are secreted at high levels. Insulin is released in decreased amounts to lower the stimulus to use blood glucose.
Catecholamine is essential in increasing blood glucose, increasing skeletal muscles, and breaking down glycogen (glycolysis) and lipids (lipolysis) to release more energy to the working body.
Increased Adrenocorticotropic (ACTH) - cortisol secretion promotes the formation of glucose (gluconeogenesis) in the liver and increased fatty acids mobilization. Glucagon increases blood glucose levels through glycogenolysis and gluconeogenesis. Antidiuretic hormone (ADH) increases to facilitate water retention to maintain plasma volume. Prostaglandins may increase to elicit local vasodilation necessary in heat dissipation, thus cooling the body.
Immune System
The immune system provides surveillance against foreign proteins, viruses, and bacteria using specialized cells synthesized by the bone marrow and thymus gland. In conjunction with the nervous and endocrine systems, the immune system influences the overall response of the body to exercise.
Moderate exercise has been proven to boost some components of the immune system: natural killer cells, circulating T- and B- Lymphocytes, and cells of the monocyte-macrophage system hence reducing the incidences of some infections and certain cancer types.
High-intensity of exercise or exercise that involves excessive training and workout has adverse effects on the immune system. High-intensity single-episode training leads to a declined functioning of all major cells of the immune system. Overtraining could reduce the response of T-Lymphocytes to mutagenic stimulation, decrease antibody synthesis, and lower the levels of immunoglobulins and complement.
Body Temperature
The maximum energy requirement for muscular work is between 20 and 25%. The remaining energy is released in a non-reusable form as heat energy which elevates the body temperature. To dissipate the excess heat generated from an increase in metabolic activities during exercise, blood supply to the skin increases which is achieved by vasodilation of cutaneous blood vessels by the inhibition of vasoconstriction.
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| To dissipate the excess heat generated from an increase in metabolic activities during exercise, blood supply to the skin increases which is achieved by vasodilation of cutaneous blood vessels by the inhibition of vasoconstriction |
Sweating is another method that eliminates the heat from the body in the process of evaporation. Further heat is lost in the exhaled air with ventilation. The hypothalamus is responsible for the regulation of body temperature.
Physical exercises induce different adaptations in human physiological processes and functions. They enhance the good health of the heart muscles, pulmonary ventilation, immune responses, thermoregulation, homeostasis, and the endocrine system. Death caused by chronic and lifestyle diseases can be greatly reduced by consistent workouts.
Adequate exercise routines must include aerobics, exercises that strengthen and maintain body strength and mass, and stretching exercises that ensure good joint mobility, flexibility, and agility.
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