During the 1975 Major League All-Star Game pre-game workout in Milwaukee, WI, Baseball Hall of Fame pitcher, Tom Seaver, approached me and started explaining the forces with which he pitched.   He said two energy masses originated in the back of his legs and moved up to his buttocks where they combined and traveled up his back to his throwing shoulder from where it flowed along his arm and exploded out his fingertips.   Tom’s proprioceptive analysis provided an entertaining image.   However, muscles come in different sizes, shapes, attachment locations and muscle fiber to motor nerve ratios.   Different muscle fiber types have different metabolic processes and nutrient sources.   Therefore, before pitchers make pitching artistic, it is a science.

     Adult humans have about two hundred and fifty million muscle fibers.   Muscle fibers contain hundreds of myofibrils.   Myofibrils contain hundreds of alternating bands of actin and myosin filaments.

     Actin filaments resemble intertwined pearl strands with thin tropomyosin protein filaments wrapped around them.   Vesicles at tropomyosin filament ends store troponin.   Troponin enzymatically inhibits muscle contraction.   Light passes through actin filament bands isotropically.   Therefore, researchers call actin filament bands, I-bands.

     Myosin filaments resemble straight line layers fused together into thick strips with numerous paddle-like myosin cross-bridge appendages arising everywhere.   Adenosine Tri-Phosphate (ATP) molecules attach to every cross-bridge tip.   Light passes through myosin filament bands anisotropically.   Therefore, researchers call myosin filament bands, A-bands.

     Adenosine and three phosphates combine to make up ATP molecules.   When two ATP molecule terminal phosphates separate, they release heat energy and one inorganic phosphate (Pi) and leave adenosine di-phosphate (ADP) behind.

     Width-wise connective tissue lines bisect actin filament I-bands.   These connective tissue lines separate contractile units.   Therefore, researchers call these connective tissue lines, Z-lines after zwischen, the German word for between.   Sarcoplasmic reticulum nervous tissue networks surround myofibrils.   At Z-lines, these nervous tissue networks have outer vesicles that store calcium.   Calcium stimulates muscle contraction.   Therefore, a contractile unit contains a one-half actin filament I-band, a whole myosin filament A-band and another one-half actin filament I-band.

     The Sliding Filament Theory explains how muscles contract.   During contractile unit relaxation, troponin inhibits actin filament movement towards the myosin filaments.   However, ten sequential events causes muscle contraction (tension).
1.   Motor nerve impulses strike muscle fiber motor end plates.  
2.   Motor end plate activations release acetylcholine into sarcoplasmic reticulum nervous tissue networks.  
3.   Sarcoplasmic reticulum nervous tissue network activations release calcium.  
4.   Calcium neutralizes troponin.  
5.   Actin filament I-bands slide over myosin filament A-bands.  
6.   Actomyosin complexes release ATPase.  
7.   ATPases severe high energy bonds between two terminal phosphate components.  
8.   Severed terminal phosphate component high energy bonds produce adenosine di-phosphate (ADP), an inorganic phosphate (Pi) and heat energy.  
9.   Heat energy tilts myosin cross-bridges away from actin filament I-bands.  
10.   Actin filament I-bands slide over flattened myosin cross-bridges.

     When muscle fibers resynthesize sufficient ATP molecules to resupply depleted myosin cross-bridges, then myosin cross-bridges straighten and return actin filaments to relaxation status.   Simultaneously, calcium returns to their storage vesicles and troponin again inhibits actin filament affinity with myosin filaments.

     Three muscle fiber types serve our wide movement requirements.  
1.   Fight or flight emergencies require muscle fibers with high intensity movements.  
2.   Until metabolic processes become fully operational situations require muscle fibers with medium intensity movements.  
3.   After metabolic processes operate efficiently situations require muscle fibers with low intensity movements.

     Emergency high intensity muscle fibers must resynthesize ATP without external resources.   They cannot wait for muscle glycogen or muscle triglyceride metabolism.   They cannot wait for oxygen transport.   Researchers name these muscle fibers, Fast Twitch I.   Because these muscle fibers resynthesize ATP with a coupled biochemical phosphogenic action, I call these muscle fibers, Fast Twitch Phosphagenic (FTP) muscle fibers.

     Fast Twitch Phosphogenic muscle fiber contractions break Adenosine Tri-Phosphate (FTP) down to Adenosine Di-Phosphate (ADP), an inorganic phosphate (Pi) and heat energy.   Phospho-creatin (PC) forms when heat energy combines creatine (C) with inorganic phosphates (Pi).   Adenosine Tri-Phosphate (ATP) resynthesizes when heat energy combines Adenosine Di-Phosphate with an inorganic phosphate (Pi).

     Fast Twitch Phosphogenic (FTP) muscle fibers require special biochemical enzymes.   FTP muscle fibers store very little phospho-creatine (PC).   Consequently, FTP muscle fibers intensely respond for about ten seconds.   FTP muscle fibers require about two minutes to recover.   Athletes cannot voluntarily activate FTP muscle fibers.   Only extremely emotional circumstances activate FTP muscle fibers.   However, during the 1968 Mexico City Olympics, longjumper Bob Beaman may have tapped into his FTP system when he set the world record by two feet.

     Short term medium intensity muscle fibers must resynthesize ATP without oxygen.   They cannot wait for oxygen transport.   Researchers name these muscle fibers, Fast Twitch II.   Fast-Twitch Glycolytic (FTG) muscle fibers metabolize glucose (C₆H₁₂O₆) to resynthesize adenosine tri-phosphate (ATP).   Because these muscle fibers metabolize muscle glycogen to resynthesize ATP, I call these muscle fibers, Fast Twitch Glycolytic (FTG) muscle fibers.

     Fast Twitch Glycolytic muscle fiber glycolysis requires twelve separate, sequential biochemical reactions that do not require oxygen.   Therefore, FTG muscle fibers are immediately available for medium intensity activities.   However, glycolysis’ waste product is lactic acid (2C₃H₆O₃).   When lactic acid accumulations reach about two and one-half ounces, FTG muscle systems cannot properly operate.   Athletes feel as though they are moving in slow motion.   Anaerobic means 'without oxygen.  ' FTG muscle fibers operate during anaerobic activities.  

     Long term low intensity muscle fibers resynthesize ATP with oxygen.   They require oxygen transport.   Researchers name these muscle fibers, Slow Twitch.   Because slow twitch muscle fibers require oxygen to metabolize muscle glycogen and muscle triglycerides, I call these muscle fibers, Slow-Twitch Oxidative (STO).   Slow-Twitch Oxidative (STO) muscle fibers metabolize the basic food cells glucose and lipids (C16H32O2) to resynthesize ATP molecules.   STO muscle fibers metabolize FTG’s lactic acid.

     STO muscle fibers contain mitachondria.   Mitachondria are subcellular structures of elaborate membrane systems that contain numerous enzymes to accelerate metabolism and ATP resynthesis.   However, mitachondria require oxygen.   Consequently, before STO muscle fibers can properly operate, the oxygen transport system must supply oxygen to mitachondrion.   The oxygen transport system takes about two minutes to get up to speed.   After the oxygen transport system supplies sufficient oxygen for metabolism and ATP resynthesis to sustain muscle contraction, STO muscle fibers effectively operate for long time periods.

     Once the oxygen transport system gets up to speed, athletes have almost inexhaustible ATP resynthesis sources.   Highly trained marathon runners can sustain oxygen transport equal to ATP resynthesis at approximately eighty percent of their maximum running intensity.   Only dehydrated blood volumes limit performances.   Aerobic means 'with oxygen.  ' Athletes activate STO muscle systems for aerobic activities.   The waste products of STO muscle systems are carbon-dioxide (CO₂) and water (H_2O).

     Green plants photosynthesize the sun’s light energy into chemical energy.   By combining green plants’ chemical energies with carbon-dioxide (CO₂) and water (H₂O), green plants manufacture four basic food molecules.   Cellulose, protein, glucose and lipids are the four basic food molecules.   Indigestible cellulose helps digestive processes.   Proteins form enzymes and filaments.   FTG and STO muscle systems metabolize glucose to resynthesize ATP.   STO muscle systems metabolize lipids to resynthesize ATP.   Green plants eliminate oxygen.

     Green plants and humans form a biological energy cycle.   Green plants consume carbon-dioxide and water.   Green plants manufacture food molecules and eliminate oxygen.   Humans consume food molecules and oxygen.   Humans eliminate carbon-dioxide and water.   Green plants consume carbon-dioxide and water, and so on, and so on and so on.

                            SUN
                             |
                        GREEN PLANTS
                             |
          (------------- chemical energy ---- food + O2 )
          ( CO2 + H2O ------ HUMANS --------------------)

     Without well-defined finite structures, actin and myosin filaments would meaninglessly quiver.   Therefore, connective tissues form well-defined finite structures within which contractile units, myofibrils, muscle fibers and muscles operate.   Myofibril z-lines join with endomysium connective tissues.   Endomysium connective tissues surround individual muscle fibers.   Perimysium connective tissues surround selective muscle fiber bundles (fasciculi).   Epimysium connective tissues surround entire muscles.   Endomysial, perimysial and epimysial connective tissue intertwine at muscle fiber ends to form tendons.   Tendons attach muscles to bones.   Connective tissues provide muscle contraction stability.

     My myofibril force theory states, “Without regard for percentages of contractile units operating, myofibrils generate the same force.  ” Myofibrils achieve maximum lengths when zero percent of contractile units operate.   Myofibrils achieve minimum lengths when one hundred percent of contractile units operate.   If athletes did not exert identical forces without regard for percentages of contractile units operating, they could not lower weights they just raised.   When activities require specific joint angles, myofibrils match contractile unit contraction percentages to specific joint angles.   Myofibril number determines strength differences.  

     When athletes grab weights with one hand from waist high tables and raise them to shoulder heights, Kinesiologists label the joint action, concentric.   Concentric means something has a common center with something else, like concentric circles.   When athletes grab weights with one hand from waist high tables, but cannot raise them, Kinesiologists label the joint action, isometric.   Isometric means the same length.   When athletes lower weights from shoulder heights to waist high tables, Kinesiologists label the joint action, eccentric.   Eccentric means deviating from the center.  

     In all three joint actions, athletes contracted biceps brachii muscles.   Biceps brachii muscles attach across elbow joints.   The three joint actions differ in whether elbow joint angles decrease, remain the same or increase.  

     Concentric, isometric and eccentric refer to three muscle contraction types.   In the three examples, the same muscles operate.   Muscles apply force only when contractile units shorten maximum resting lengths.   Muscles contract in only one way, not three.   Therefore, these names are without meaning.  

     The phenomenon actually refers to changing joint angles.   Names assigned to phenomenon should describe the phenomenon.   Therefore, the following names describe the three joint actions.  

     In concentric muscle contractions, the joint angles across which contracting muscles operate decrease.   The Greek word for less is ‘meion’ and the Greek word for angle is ‘angkylos.  ’ Mioanglos properly describes the joint action.   Therefore, Mioanglos Joint Action means that the joint angles across which contracting muscles operate decrease.  

     In isometric muscle contractions, the joint angles across which contracting muscles operate remain the same.   The Greek word for equal is ‘isos’ and the Greek word for angle is ‘angkylos.  ’ Isoanglos properly describes the joint action.   Therefore, Isoanglos Joint Action means that the joint angles across which contracting muscles operate remain the same.  

     In eccentric muscle contractions, the joint angles across which contracting muscles operate increase.   The Greek word for more is ‘pleion’ and the Greek word for angle is ‘angkylos.  ’ Plioanglos properly describes the joint action.   Therefore, Plioanglos Joint Action means that the joint angles across which contracting muscles operate increase.  

     Motor nerve cells accompany blood vessels under endomysial connective tissues to individual muscle fibers.   Nerve cells have one nucleus, several dendrites, one axon and one synaptic knob.   Motor nerve cells have indented myelin sheaths surrounding their axons.   Myelin sheaths protect against unwanted electrical disturbances and accelerate nerve impulse conduction velocities.   When stimulated, sodium molecules enter nerve cell bodies and change the electrical polarity.   At eleven millivolt polarity, nerve cells send their nerve impulses down their axons to their synaptic knobs.   Non-myelinated axons conduct nerve impulses at between thirteen and twenty-two miles per hour.   Myelinated axons conduct nerve impulses at between one hundred and thirty-five and two hundred and twenty-five miles per hour.  >/P>

     Motor nerve synaptic knobs attach to muscle fibers at motor end plates.   Synaptic knobs contain mitachondria.   Mitachondria resynthesize acetylcholine.   Acetylcholine stimulates sarcoplasmic reticulum tubule and vesicle networks.  

     Approximately four hundred and twenty thousand motor nerves supply approximately two hundred and fifty million muscle fibers.   However, motor nerves do not innervate the same number of muscle fibers.   Fine control motor nerves, like eye muscles, innervate only about twenty-five muscle fibers.   Moderate control motor nerves, like hand muscles, innervate about four hundred muscle fibers.   Gross control motor nerves, like lower leg muscles, innervate about two thousand muscle fibers.   Motor units consist of one motor nerve and its muscle fibers.  

     Activities have specific motor unit contraction and relaxation sequences.   Simple motor skills, like bicycle riding, have simple motor unit contraction and relaxation sequences.   Complicated motor skills, like baseball pitching, require complicated motor unit contraction and relaxation sequences.   Complex motor skills require more perfect practice of its motor unit contraction and relaxation sequence.  

     After thousands of perfect motor unit contraction and relaxation sequence practices, athletes’ central nervous systems permanently align their protoplasmic nerve tissues.   Researchers label these permanent specific protoplasmically aligned central nervous system tissues, engrams.   During competitions, superior athletes automatically activate engrams.   Therefore, athletes must practice activities’ motor unit contraction and relaxation sequence perfectly.  

     Athletes injure muscles in different ways.   When athletes improperly apply force, they strain mal-aligned muscles.   When athletes vigorously increase motion ranges, they tear connective tissues.   When athletes generate high velocity limb movements beyond physiological deceleration limits, muscle tissues tear.   Improper motor unit contraction and relaxation sequence programming tears muscle tissues.  

     Improper force application injuries occur most commonly.   Pitcher injuries usually result from improper force application techniques.   Biomechanists and kinesiologists have the professional responsibility to determine the proper force application techniques for all physical activities.   Unfortunately, they have failed to meet their obligations.  

     Increasing ranges of motion injuries occur because coaches train athletes to avoid ranges of motion injuries.   Coaches routinely recommend ‘stretching’ exercises.   They claim stretching exercises increase flexibility.   Stretching exercises apparently increase ranges of motion about specific joints.   However, stretching exercises do not increase myofibril lengths.   Stretching exercises trains athletes to use fewer contractile units to maintain specific joint stabilities.   When fewer contractile units contract, myofibril lengths increase.   However, contractile units, myofibrils and muscle fibers do not stretch, they are finite length tissues.  

     Toe touches provide an interesting example.   Toe touches increase athletes’ knees-locked toe touch range of motion.   However, they did not stretch their ‘hamstring’ muscles.   Biceps femoris’ long head, semimembranosis and semitendinosis muscles (hamstring muscles) stabilize hips and torsos during toe touches.   Therefore, they cannot stretch when contracting.   Actually, because athletes use fewer myofibril contractile units to stabilize their hips and toe touches, their myofibrils are longer.  

     To prevent high velocity deceleration muscle injuries, the cerebellum regulates these velocities.   The cerebellum restricts limb velocities below deceleration capacities.   However, during emotional competitions, athletes sometimes exceed deceleration capacities.  

     When muscles powerfully contract while opposing (antagonist) muscles are contracting, antagonist muscle fibers tear.   Tearing ‘hamstring’ muscles is a good example.   When athletes mis-program their sprinting motor unit contraction and relaxation sequence, they tear their biceps femoris muscles’ short head.   When the central nervous system sends contraction signals to muscles, they also send inhibitory signals to their antagonist muscles.   However, the biceps femoris muscle’s short head receives its inhibitory signal from a different sensory nerve than the other ‘hamstring’ muscles.   Consequently, the biceps femoris muscles’ short head inhibitory signal arrives late and the powerful antagonistic muscle contraction tears the biceps femoris muscles’ short head.  

     When body builders pose, they co-contract antagonistic muscles.   For example, they contract biceps brachii and triceps brachii muscles simultaneously without injury.   These co-contractions occur without meaningful joint actions.   These are co-contractions without joint actions.   However, co-contractions with joint actions tear muscles.   The biceps femoris muscles’ short head and plantaris muscle are two examples.  

     Muscle tears require rehabilitation.   When improper force application techniques tear muscles, athletes must learn proper force application techniques.   Until athletes can perform proper force application techniques without tearing injured muscles, they should use cold-induced vaso-dilation.   Cold-induced vaso-dilation means pack injured regions with ice.   Athletes conform gallon zip-locked plactic bags filled with crushed ice around injured regions directly against skin.  

     Ice coldness initially vaso-constricts effected blood vessels and reduces blood flow.   Blood flow deprivation causes effected muscles to emit pain signals for oxygen deprivation (hyperemia).   Oxygen-deprived muscle cells eventually die.   However, reactive hyperemia prevents oxygen-deprived muscle cell deaths.   Reactive hyperemia vaso-dilates blood vessels serving oxygen-deprived muscle cells.   Vaso-dilation floods injured muscle cells with healing blood.   Therefore, throughout rehabilitations, injured athletes should use cold-induced vaso-dilation.  

     In the October 1, 1907 American Journal of Physiology, Warren P.   Lombard and F.   M.   Abbott published, "The Mechanical Effects Produced by the Contraction of Individual Muscles of the Thigh of the Frog.  " Lombard and Abbott sought to explain how the muscles on the front and back of the thigh contracted simultaneously when humans stood up from sitting positions.   They analyzed the actions of twenty-two muscles of the thigh and hip.   They offered lever and pulley explanations.   Kinesiologists accepted their theory and called it, 'Lombard's Paradox.  '

     However, frogs do not have hips.   The ‘quadriceps’ muscles, vastus lateralis, vastus intermedialis and vastus medialis, straighten the knee joint, but the ‘hamstring’ muscles, biceps femoris’ long head, semimembranosis and semitendinosis, straighten the hip joint.   The biceps femoris’ short head does also straightens the hip joint.   When people stand up from sitting, they first bend forward at their waists.   To bend forward at their waists, they use their ‘hamstring’ muscles to stabilize their hips.   Then, they use their ‘quadriceps’ muscles to straighten their knees.   The concurrent muscle actions cause the simultaneous ‘hamstring’ and ‘quadriceps’ muscle contractions.  

     When limbo dancers move under low bars with their hips thrust forward and thorax and heads leaning way back, they straighten their bodies without straightening their hip joints.   Pregnant women stand up from sitting without straightening their hip joints.   Both keep their thorax and heads backward and use the muscles that bend the hip forward to remain upward.  

     Everybody can do similarly.   First, stand up from the front edge of a chair with your thorax and head leaning forward.   You will find that the ‘hamstring’ and ‘quadriceps’ muscles contract simultaneously.   Second, stand up from the front edge of a chair with your thorax and head leaning backwards.   You will find that only the ‘hamstring’ muscles contract.   Therefore, when people stand up from sitting with their thorax and head leaning forward, co-contraction with joint action does occur, but at very controlled velocities.