Although a light-hearted attitude may prevail, as it often times does among persons studying fitness, learning scientific concepts and principles of fitness is a prerequisite for success in the area of fitness-training.  Because the study of fitness involves the study of scientific principles, sometimes, it demands a level of concentration that is equivalent to that required in the study of science.  However, anyone who is willing to make an earnest effort to learn about fitness will determine that the scientific topics studied and discussed in this course are easily understood.  Five scientific disciplines, which focus on the study of the human body and how it responds to physical activity, are chemistry, biology, anatomy and physiology, physiology of exercise, and biomechanics (physics).  Research in these disciplines has revealed what we need to know about the management of fitness-training programs to achieve higher levels of fitness and sport performance.

This course is divided into three parts.  It allocates the first to the theories and principles of science, which prepare students for an understanding of how the design of the human body allows it to respond to physical activity.  The second section introduces students to theoretical models of fitness activities, which may be used to identify, analyze, and plan for an individual’s fitness and conditioning needs.  There are eight components of fitness covered in this course: flexibility, cardio respiratory endurance, strength, skill, body mass composition, energy, nutrition, and strategy.  The third section of this course entertains the area of program design.  In this section the concepts and principles of fitness and conditioning already presented in the first two sections are applied to develop three eight-week training programs, each of which represents one training cycle of three different training periods for a given year, pre-season, in-season, off-season, and post-season; a year may be divided into four periods: pre-season, in-season, off-season, post-season.  The purpose of the third section is to give you an opportunity to learn and practice the concepts and principles covered and observed in this course on how to enhance the levels of participation and performance of individuals and athletes in their daily lives.

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The Science of Fitness 

The study of fitness and conditioning is commensurate with the study of science.  This viewpoint is supported by the realization that an understanding of fitness requires an understanding of the human body, and that there are many branches of science, which contribute to this enlightenment.  Thus, it is logical to conclude that the study of fitness should begin with the study of science.  Five branches of science that contribute to an understanding of fitness and conditioning are given in Table 2.1.  The concepts comprising this table are essential for an understanding of how physical activity influences body functions to improve or maintain desirable levels of fitness.

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The most critical concepts needed to achieve an awareness of how fitness is attained in the human body are embodied in the five scientific disciplines listed above.  All of these disciplines have contributed to an understanding of how the organizational and structural hierarchy of the human body ( chemistry, organelles, cells, tissues, organs, and organ systems) are affected by physical activity.   A discussion of the relationships of the structural hierarchy of the body to the study of fitness is essential for an understanding of how fitness is affected by physical activity and how physical activity can be regulated to achieve optimal functioning and improved levels of performance.  Although this knowledge is, generally, accomplished through contributions from the five scientific disciplines listed above, most of what we learn about the principles of sport fitness is derived from the study of exercise physiology, which includes findings from the other scientific disciplines.  However, you are advised to remember that an understanding of some concepts and principles, regarding fitness, can only be acquired by studying appropriate topics in the other scientific disciplines.

Basic chemistry explains how the components (chemicals) of matter, the materials of which gases, liquids, and solids making up the body are constructed, interact to cause specific outcomes, such as the creation of energy for muscle activity.   Biochemistry or biological chemistry, the chemistry of living things, and organic chemistry, the chemistry of carbon compounds, are two important branches of chemistry that are closely linked and utilized to help us achieve an understanding of the functions of the human body.  Basic chemistry and biochemistry (the chemistry of living material) provide the background needed to understand body functions.  That is, chemistry underlies all physiological processes, including movement, the pumping of your heart, and the management of your thoughts.  Therefore, the study of fitness is influenced by the study of chemistry. 

Knowledge gained through the study of biology, which is defined as the science that deals with living things, is based on the laws of physics and chemistry.  However, since biology applies the laws of these two disciplines to understand living things and since there are so many processes and areas of study related to living things, biology is divided into many special areas of study to advance our knowledge of the human body, including knowledge of fitness.  Another special area of biology is anatomy and physiology.  Anatomy is the study of the form or structure of body parts and how these parts relate to one another.  Physiology deals with the functioning of the structural machinery of the body as it relates to how the parts of the body work and carry out the activities that maintain life.  Because anatomy and physiology can be studied separately, there must be a unique benefit that comes from the study of these disciplines together.  When physiology is combined with the study of anatomy, structure and function are combined to gain new perspectives as to how the constituent parts of living organisms interact to maintain ideal conditions for life.  Thus, the focus of anatomy and physiology is the relationship of structure to function or the principle of complimentarity of structure and function.  That is, function is determined by structure; what a structure can do depends on its specific form.  For example, bones provide support and protection to body organs, but it is the hard mineral deposits of which bones are constructed that make these functions possible.  Of course, the ideas above makes the study of biology and anatomy valuable sources of man's knowledge of sport participation and performance.

When the study of anatomy and physiology are combined with other sciences to determine the effect of exercise on the body physiology of exercise is actualized.  This branch of science is often divided into three main divisions: exercise, health fitness, and performance.  No matter what the focus of the various sciences may be, including physiology of exercise, all of them must include the organizational hierarchy of the structures making up the human body.  Therefore, as the study of fitness unfolds the focus of each lesson can be shifted to the activities of chemical elements, organelles, cells, tissues, organs, and organ systems and to how these levels serve as the mechanism for improving sport performance and participation.

The musculoskeletal system (two systems) of the human body are organized to function together according to the unique cells and tissues of which they are made.  It is formed of bones, joint connectors, and muscle groups that make movement possible.  These structures are configured in many ways to allow a great variety of movements or activities.  Knowledge of how the musculoskeletal anatomy makes movement possible involves the study of forces or biomechanics.   This scientific discipline identifies the mechanisms through which movement is created to explain the safest and most efficient patterns of movement. For example, knowledge of the best way to perform a spike in the game of volleyball or the bench press in resistance training is acquired through the study of biomechanics.  However, in order for muscles to move and bones to harden to make movement possible, energy must be provided for these capabilities along with hundreds of other human functions. Thus, the study of forces, as are all other studies presented in this lesson, is interconnected with the study of body functions and therefore the study of other scientific disciplines.

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Levels of Structural Complexity 

To understand how physical activities influence the functions of the human body, no matter where individuals start their journey, they must consider the levels of structural complexity before they can grasp the true meaning of fitness and conditioning.  

The human body incorporates many levels of structural complexity.  The simplest level of this structural hierarchy is the chemical level.  At this level, atoms, tiny building blocks of matter, are acted upon by a variety of physical and chemical forces that make them attractive to each other and form molecules, such as water, sugar, and protein and acids and bases, which are two classes of biologically important compounds.  Through the study of chemistry, scientists have learned that there is a natural tendency for molecules of different types to completely mix with each other.  This is because each molecule is moving constantly.  Their movement is random and due to the energy found in the individual molecules.  This motion produces energy, which remains constant in the universe, thefirst law of thermodynamics.  Therefore, energy can neither be created nor destroyed.  However, energy can change from kinetic energy, the energy of motion, to potential energy, the energy an object has due to its position and vice versa; potential energy can change to kinetic energy.  Whenever energy is converted from one form to another, some useful energy is lost.  This statement is the second law of thermodynamics.  The loss of energy may be released as heat or stored as chemical energy in the form of some useful compound (potential energy).  One example is the use of adenosine triphosphate or ATP, a compound that supplies energy to body cells for biologic work, including muscle contraction.  The potential energy within the ATP molecule is then utilized for all the energy-requiring processes of the cell.  This energy receiver-energy donor cycle, in essence, represents the two major energy-transforming activities in the cell: 1) formation and conservation of ATP from the potential energy in food, and 2) use of the chemical energy in ATP for biologic work.  There will be more discussion about energy in the following lessons.

At the chemical level of the structural hierarchy of the human body, molecules, which are formed by the attractive nature of atoms making up various elements, associate in very specific ways to form organelles, basic components of the microscopic cells.  Cells, comprised of organelles, are the smallest living structural and functional units of an organism.  Individual cells vary widely in size and shape according to the unique functions that they have in the body.  All cells utilize nutrients and maintain their boundaries, but only certain cells can perform specific functions.  For example, there are certain cells in the eyes that form the transparent lens of the eye, secrete mucus, or conduct nerve impulses.   

The study of living things has revealed that the cell is the minimal unit that displays all the characteristics of life.  It is necessary to understand the structure and workings of this basic unit to understand a complex organism, such as the human body.  Analysis shows that a cell is composed of many basic chemicals found in nature.  Those elements are bound together in special ways and arranged into complex molecules, which are in turn fashioned into more complex structures.  Biologically important chemical reactions are controlled by the cell and responsible for the breakdown of nutrients and the manufacture of their own essential molecules.  Understanding how cells are constructed and how they work enables scientists to control their functions for the benefit of all. 

The simplest form of living organisms are composed of single cells, but in human beings, the hierarchy continues to the tissue level.  Tissues consist of groups of similar cells that have a common function.  Ultimately, each basic group of biological functions performed in the body is determined by a coordinated group of tissues, called organs.  The four basic tissue types in the body are the epithelial tissue (also called epithelium), muscle tissue, connective tissue, and nervous tissue.  Each of these tissue types has a characteristic role in the body.  Epithelium covers the body surface and lines its cavities; muscles cause movement; connective tissue supports the body and protects its organs; and nervous tissue provides a means of rapid internal communication by transmitting electrical impulses.

Epithelial tissues perform a wide variety of functions, including protection, absorption, secretion, and sensation.  The epithelial layer of the skin -- the epidermis -- covers the entire body and protects it from threats such as mechanical injury, chemicals, bacteria, and fluid loss.  The epithelial tissue lining the digestive tract absorbs nutrients and water into the body.  Some epithelial cells are organized into glands that secrete cell products like hormones, enzymes, or sweat.  Other epithelial cells are specialized as sensory receptors that receive information from the environment.  For example, epithelial cells in taste buds and the nose are specialized as chemical receptors.

Everything that enters or leaves the body must cross one or more layers of epithelium.  Food taken into the mouth and swallowed is not really “inside” the body until it is absorbed through the epithelium of the gut and enters the blood.  To a large extent, the ability of epithelial tissues to let matter pass through its surfaces regulates the exchange of substances between the different parts of the body, as well as, between the body and the environment.

Muscle tissue is specialized to contract.  Movements is the result of the contraction of elongated, cylindrical, or spindle –shaped cells of muscle tissue.  Each cell comprising muscle tissue is referred to as a fiber because of its length.  A muscle fiber or cell contains many thin, longitudinal, parallel contractile fibers called myofibrils. Two proteins, myosin and actin, are the chief components of myofibrils, and play a key role in contraction of muscle cells, which are classified into three types: smooth, skeletal, and cardiac.  Smooth muscle is located on the walls of the digestive tract, blood vessels, and certain other internal organs.  Each of its spindle-shaped fibers contain a single nucleus.  Skeletal Muscles make up the large muscle masses attached to the bones of the body. Skeletal muscle fibers are very long (about 1 inch) and have many nuclei, an exception to the generalization that cells contain only one nucleus.  And they are located so that the entire central part of the skeletal muscle fiber is utilized as contractile units.  Unlike smooth and cardiac muscles, which are not normally regulated at will, skeletal muscle fibers are generally under voluntary control. 

A microscopic view of skeletal and cardiac fibers reveal that they have alternating light and dark transverse stripes, or striations, that change their relative sizes during contraction.  Striated muscle or skeletal and cardiac muscle can contract rapidly, but they cannot remain contracted for a long period of time.  They must relax and rest momentarily before contracting again.  This observable fact supports concerns for rest as an essential aspect of fitness training.

Cardiac muscle is the main tissue of the heart.  The fibers of cardiac muscle are joined end-to-end, and they branch and rejoin, forming complex networks.  Most of us have no conscious control over how fast our heart beats.  Key words to remember for this muscle type are cardiac, striated, and involuntary.  Cardiac muscle usually contracts at a fairly steady rate set by the heart’s pacemaker, but neural controls allow the heart to shift into high gear for brief periods, as when you race across the tennis court to make an overhead smash. Collectively, the three types of muscle found in the body perform four important functions: they produce movement, maintain posture, stabilize joints, and generate heat.  The most popular theory about muscle growth is that we are borne with a specific quantity of muscle fibers that can be activated.  These fibers, depending on the amount of physical activities materialized, are either activated or thickened, which is hypertrophy, or they are inactivated and become flaccid, a condition called atrophy.

If you examine the organs of the body, you will find that almost every organ has connective tissue that supports and cushions its structures. It is the most abundant and widely distributed type of tissue in the body.  It also exists in more varied forms than any of the other tissue types, as connective tissue is found in skin, membranes, muscles, bones, nerves, and all internal organs.  The functions of connective tissue are varied.  It connects tissues to each other and forms a supporting framework for the body as a whole and for its individual organs.  Blood, a form of fluid connective tissue, transports substances throughout the body. It also exists as delicate paper-thin webs, strong and tough cords, and rigid bones that protect and hold internal organs together. 

All five of the connective tissues explained above, as do the other types of tissues in the body, respond to physical activity.  As physical activity is experienced or not experienced, they adapt more or less.  Thus, the functions at each level of the structural hierarchy of the body become more efficient or less efficient, according to the type and level of activity experienced.

Connective tissue contains three types of fibers: collagen, elastic, and reticular.  The collagen fibers are the most numerous.  When collagen is not produced in sufficient amounts, the bones become over dense and brittle; and they are easily broken.  This is a defect that occurs at birth, Osteopetrosis, not Osteoporosis.  It is the results of an imbalance between the formation of bone and the breakdown of the bone.  Symptoms can include fractures, frequent infections, blindness, deafness, and strokes. Many desirable characteristics are present in the body as a result of the different kinds of connective tissues that exist.  However, in the absence of sufficient exercises functional imbalances can occur, which are analogous to Osteoporosis, brittle bones as the body ages.  This means that cellular activities reverse the adaptation process to make the functions of the body less efficient in the absence of sufficient exercise and proper nutrition.

Nerve tissue consists of two basic kinds of cells: nerve cells, or neurons, which are functional or conducting units of the nervous system, and special connecting and supporting cells called neuralgia.   All neurons are characterized by a single cell body and two types of processes: one axon, which transmits a nerve impulse away from the cell body, and one or more dendrites which carry impulses toward the cell body.  The basic function of nervous tissue is to make rapid communication between body structures and control of body functions possible.  Certain nerve damage is irreversible because the genetic code responsible for the healing of neurons is turned off.  However, it is important to realize that all types of connective tissues can respond, favorably, to fitness activities.

The next level of organization in the structural complexity of the human body is the organ level.  At the organ level, extremely complex physiological processes become possible.  An organ is a discrete structure composed of at least two tissues types.  The stomach is a good example of an organ: its lining is an epithelium that produces digestive juices; the bulk of its wall is composed of muscle that acts to churn and mix stomach contents (food); its connective tissue reinforces the soft muscular walls; and its nerve fibers increase digestive activity by stimulating the muscle to contract more vigorously and the glands to secrete more digestive juices.  The liver, the brain, and a blood vessel are very different from the stomach, but they are organs as well.  You can think of each organ of the body as a specialized functional center responsible for necessary activity that no other organ can perform.  Ultimately, these basic types of tissues determine the variety of biological functions performed in the body as a coordinated group of tissues, called organs and all of them respond favorably to fitness activities. 

The next level of organization is the organ system level.  Organs that cooperate and work closely with one another to accomplish a common purpose are said to be part of a particular organ system. For example, organs of the cardiovascular system, mainly the heart and blood vessels, ensure that blood containing nutrients, oxygen, and other vital substances are continuously circulated to all body cells.  Organs making up the digestive system, the mouth, esophagus, stomach, intestine, and so forth, break down ingested food so that the nutrients can be absorbed into the blood.  The digestive system also removes indigestible food residues from the body.  The organ systems of the body that must be considered, understood, and evaluated, in regard to their relationship, adaptation, and contribution to fitness, are the cardiovascular, respiratory, digestive, integumentary, skeletal, muscular, nervous, endocrine, and  organ systems.

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Summary

Contributions from many scientific disciplines have revealed that the human body responds in a variety of ways to physical activities.  Five disciplines that have contributed to the formulation of the scientific concepts that are essential for the successful creation of fitness training programs are chemistry, biology, anatomy and physiology, physiology of exercise, and biomechanics.  The use of phenomenon or concepts and principles of training (discussed in Lesson 2) discovered through the study of these five disciplines have paved the way for the design of more effective fitness training programs, which may ensure the attainment of optimal levels of body functioning and higher levels of fitness.  Knowledge and understanding of the scientific concepts and principles discovered by scientists are necessary to achieve outstanding performance in various recreational and competitive sports.  The responses of the body to physical activities prepare it for improved well-being and better participation in sports.  For this reason, another name for physical activities is fitness activities, which are physical activities that improve body functions.  Fitness activities may be classified according to their affect on four areas of fitness that should be emphasized in fitness-training programs.  They are flexibility, cardio respiratory endurance, muscular strength, and body fat composition.  The levels of fitness achieved in these areas are dependent upon the adaptations that occur throughout the structural complexity or organizational hierarchy of the body, which begins at the chemical level and progresses to organelles, cells, tissues, organs, and organ systems level.  Each level of organization contributes to the level of fitness attained, maintained, or loss in four components of fitness.

At the chemical level, all of the molecular and structural interactions necessary for life are also essential for the adaptations that result from physical activities.  These processes become more organized and complex at each higher level.  they move from organelles to the cells, the smallest living structural and functional units of the body to tissues, the second functional level of organization.  Then, the organ level of organization, which further specializes the capabilities of the body’s functions, becomes a factor.  This level of function utilizes unique body parts from different tissues to perform special functions in the body.  The final level in the process is the organ systems level; this level reveals how activities at all other levels of the body complement each other through the thousands of complex functions needed to sustain and adapt the body to what it experiences. 

Due to the responses of the structural complexity of the body to physical activities, muscles become more dense by activation of a greater number of muscle cells, which increases work against resistance and makes them longer to permit greater range of motion in joints; the heart and blood vessels transport more blood to increase the ability of the body to use oxygen; and less fat is stored in the body, which reduces the percentage of body fat contained in the body, thereby improving optimal functioning and performance.  In the absence of appropriate fitness activities these effects are reversed.

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