3) EXERCISE SCIENCE for training subject in sports

Exercise physiology

1. EXERCISE SCIENCE 2 BFY SPORTS N FITNESS BFY SPORTS N FITNESS

2. WHAT MAKES THE BODY GO ? Energy is what makes us go, that which gives us the ability to carry out work. Several kinds of energy – light, electrical, thermal, chemical, mechanical. Ultimate source of all energy is the sun. Energy can neither be created nor destroyed, however it can be transformed and transferred. Energy that can be utilized by a cell in order to carry out metabolism is ATP BFY SPORTS N FITNESS

3. Aerobic metabolism is the supply of ATP in the presence of adequate oxygen at the cellular level Anaerobic metabolism is the supply of ATP in the lack of oxygen at the cellular level Muscle fiber in order to contract requires ATP which has to be cleaved The body’s cells require energy in the form of ATP. Since only a small amount of ATP is stored in the body, food (fat, carbohydrates, and protein) must be broken down into its simplest components (fatty acids, glucose, and amino acids, respectively), which are used to produce ATP or stored for later use. The cleaving or breakdown of ATP releases energy while the synthesis of ATP requires energy BFY SPORTS N FITNESS

4. Supplying the Body With Energy BFY SPORTS N FITNESS

5. PHOSPHAGEN SYSTEM Immediate source Comprises stored ATP (1-3 sec) and creatinine phosphate. Lasts for 8-10 secs High power i.e. very high to high intensity activity is utilizes this source primarily Anaerobic BFY SPORTS N FITNESS

6. ANAEROBIC GLYCOLYSIS It is the breakdown of glucose in an anaerobic manner The end product is lactic acid which inhibits muscle contraction and heat Lasts for 2-3 mins Fuels high intensity to moderately high intensity work Produces 2 ATP per glucose molecule BFY SPORTS N FITNESS

7. AEROBIC SYSTEM This is a long term source of energy It can utilize carbs, fats and protein as fuel in the presence of oxygen Most of the reactions of this system occur within the mitochondria It is the primary system supplying energy for work lasting more than 3 mins It produces 38 ATP per glucose molecule and hundreds of ATP per fat molecule depending on its length. BFY SPORTS N FITNESS

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9. Muscle-fiber Microanatomy Skeletal muscles are made up of many muscle fibers held in place by connective tissue (fascia). Muscle fibers are made up of myofibrils (protein filaments) composed of a series of repeating segments called sarcomeres. Sarcomeres, made up of thick (myosin) and thin (actin) myofilaments , are the functional contracting unit of skeletal muscle. BFY SPORTS N FITNESS

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11. Mu s c l e C o n t r a c t I o n BFY SPORTS N FITNESS

12. SLIDING FILAMENT THEORY OF MUSCLE CONTRACTION When acetylcholine is released from the CNS and detected, calcium is released. Calcium exposes binding sites along the actin for the myosin to attach. If sufficient ATP is present, cross-bridges are formed and the myosin pulls the actin toward the center, thereby shortening the sarcomere (all sarcomeres shorten simultaneously) and the muscle fiber itself. If multiple muscle fibers are stimulated to contract at the same time, the muscle will try to actively shorten by contracting. BFY SPORTS N FITNESS

13. TYPES OF MUSCLE CONTRACTION Concentric/ shortening- muscular force is able to overcome external resistance Eccentric/ lengthening- external resistance too great for muscular force Isometric/ static- muscular force equals external resistance Isokinetic - the speed of contraction is the same throughout the range of motion. Specialized machines are required for this. BFY SPORTS N FITNESS

14. TYPES OF MUSCLE FIBRES Slow twitch/ type I- these are slow to contract and produce small amounts of force but they have great resistance to fatigue High number of mitochondria; aerobic glycolysis and fatty-acid oxidation They produce most of their ATP aerobically in the mitochondria and are therefore also called oxidative fibers . dense capillarization to deliver oxygen. Well equipped for oxygen delivery High number of oxidative enzymes Used for low-intensity, longer-duration activities (e.g., walking, jogging, swimming) Usually more abundant in fatigue-resistant muscles (e.g., postural muscles) BFY SPORTS N FITNESS

15. Fast twitch/ type IIb / glycolytic- fast contracting muscle fibers capable of generating great force. Produces ATP by phosphagen and anaerobic glycolysis but fatigues easily. Contain larger quantities of enzymes required for anaerobic metabolism Utilize primarily the phosphagen and anaerobic glycolysis energy systems Specialized for anaerobic metabolism FT motor units innervate more muscle fibers, allowing greater force production. Fast oxidative glycolytic/ type IIa - capable of producing great force and fatigue resistant. Contains both aerobic and anaerobic enzymes. BFY SPORTS N FITNESS

16. There is usually a combination of both fiber types in all muscles [ Most people have about equal percentages of FT and ST fibers.] with certain muscles having a predominance of one fiber type over the other in accordance with its function There is a genetic variation in fiber proportion from person to person. [ Muscle-fiber distribution is largely determined by genetics.] Persons better at low-intensity endurance activities may have a larger percentage of ST fibers. Persons better at high-intensity, sudden bursts of activity probably have a larger percentage of FT fibers. Type I cannot be converted to type II and vice versa. However type IIb can be shifted towards type IIa through specific training. [ “Intermediate” fiber types have a high capacity for both fast anaerobic and slow aerobic movements, and are adaptable based upon the training stimulus.] Order of recruitment of muscle fibers is from type I to type IIa to type IIb as the intensity of exercise increases. BFY SPORTS N FITNESS

17. Muscle Fiber Response to Training All three muscle fiber types are highly trainable. Adapt to the specific demand placed on them Muscle fiber types are recruited sequentially in response to force generation: ST then FT FT muscle fibers are more closely related to the hypertrophy (increase in size) of fibers in response to a strength program. Muscular endurance training is specific to both ST and FT fibers and motor units . BFY SPORTS N FITNESS

18. Type I Type IIa Type Iib Speed of contraction Low Medium High Force capacity Low Medium High Fatigue resistance High Medium Low Mitochondrial content High Medium Low Size Low Medium High Efficiency High Medium Low Aerobic capacity High Medium Low Anaerobic capacity Low Medium High The following table compares the three types of muscle fiber using the relative terms low, medium, and high. BFY SPORTS N FITNESS

19. FACTORS AFFECTING FORCE PRODUCTION IN A MUSCLE Number and type of motor unit stimulated Frequency of stimulation Limb length and anatomical insertion of tendon Gender Age BFY SPORTS N FITNESS

20. Musculotendinous Receptors Muscle spindle Located in the muscle belly lying parallel to the fibers Causes a reflexive contraction (stretch reflex) in the muscle when the muscle senses a stretch force. It simultaneously causes the antagonist to relax (reciprocal inhibition). GTO Located between the muscle belly and its tendon Causes muscle inhibition (autogenic inhibition) when it senses tension. BFY SPORTS N FITNESS

21. REFLEXES CONCERNED WITH MUSCLE CONTRACTION The stretch reflex – brought about by muscle spindle. There is a reflex contraction of the muscle if it is stretched suddenly or forcefully or excessively Autogenic inhibition – brought about by the golgi tendon organ. There is a relaxation of the muscle if there is excessive tension generated which can injure the tendon (prolonged stretch or extreme contraction) BFY SPORTS N FITNESS

22. Reciprocal innervation/ reciprocal inhibition – when a muscle is contracting against resistance, its opposing muscle will relax and vice versa Co-contraction – if a body part is statically held when gravity is not acting upon it, opposing groups of muscles will contract simultaneously to hold it in place, provided none of them is the prime mover. BFY SPORTS N FITNESS

23. HOW DOES OXYGEN REACH THE WORKING MUSCLES ? BFY SPORTS N FITNESS

24. Oxygen Delivery Oxygen delivery is a function of cardiac output (the quantity of blood pumped per minute). Cardiac output (Q) = Stroke volume (SV) x Heart rate (HR) (in beats per min) Stroke volume is the amount of blood pumped during each heartbeat. Cardiac output increases due to increases in both SV and HR. HR typically increases in a linear fashion up to maximal levels. SV increases to about 40–50% of maximal capacity, and then plateaus. BFY SPORTS N FITNESS

25. HEART RATE the number of times the heart beats in one minute. Normal HR is 60-100 beats/ min Contraction- systole and relaxation- diastole . A systole and diastole of either atria or ventricles together makes up a cardiac cycle . If the average heart rate at rest is considered to be 72 beats/ min, the duration of a cardiac cycle is 0.8 sec. Tachycardia is a heart rate greater than normal Bradycardia is heart rate lesser than normal BFY SPORTS N FITNESS

26. STROKE VOLUME It is the amount of blood that is pumped out by the left ventricle per beat. Average SV is 80 ml per beat Stroke volume can only increase upto a limit as exercise intensity increases End diastolic volume- blood left in the ventricle at the end of ventricular relaxation, just prior to contraction Ejection fraction- the percentage of end diastolic blood that is pumped out per beat BFY SPORTS N FITNESS

27. CARDIAC OUTPUT It is the amount of blood pumped out of the heart into the systemic circulation per minute It is a product of HR and SV Cardiac output increases as the intensity of activity increases An increase in cardiac output is an indicator of increased oxygen delivery BFY SPORTS N FITNESS

28. Oxygen Extraction Oxygen extraction from the blood at the cellular level depends on muscle fiber type and the availability of specialized oxidative enzymes. Slow-twitch muscle fibers are specifically adapted for oxygen extraction and utilization. Aerobic production of ATP occurs in the mitochondria of the cells. The circulatory system increases blood flow to the active muscles and decreases blood flow to non-active areas such as the viscera, allowing a higher concentration of O 2 to be extracted. BFY SPORTS N FITNESS

29. Capillarization allows more blood to flow slowly by the muscle fibers thereby making time for oxygen extraction Oxygen extraction takes place in the muscle fibers through mitochondrial enzymes Oxygen uptake (VO2 ) is determined by oxygen delivery and oxygen uptake, however oxygen extraction and not oxygen delivery is the limiting factor in oxygen uptake BFY SPORTS N FITNESS

30. Oxygen Consumption The more oxygen a person can take in, deliver, and utilize, the more work he or she can perform. VO 2 max refers to one’s maximal oxygen consumption. It is expressed in either “relative” terms (mL/kg/min) or “absolute” terms (L/min). Relative VO 2 max allows comparisons between individuals. Absolute VO 2 max is used to determine caloric expenditure during specific activities. Approximately 5 kcal of energy are burned for every liter of oxygen consumed. BFY SPORTS N FITNESS

31. Oxygen Consumption During Aerobic Exercise As soon as aerobic exercise begins, more ATP is required. To meet this demand, the body’s sympathetic nervous system takes over and stimulates an increase in cardiac output and the release of epinephrine and norepinephrine, which prepare the body for increased metabolic demands. Once exercise begins, it takes two to four minutes for the body to meet the increased metabolic demand of oxygen. During this time, the anaerobic energy systems take over. When the cardiorespiratory system has fully taken over, a new level of steady-state oxygen consumption is achieved . BFY SPORTS N FITNESS

32. Return of Oxygen to Resting Levels Cardiac output, blood pressure, and ventilation return to resting levels. Oxygen consumption slowly declines, but remains elevated above resting level—excess post exercise oxygen consumption (EPOC). During this time, phosphagen stores are being replenished, remaining lactate is being removed from the blood, the metabolic rate decreases, etc. BFY SPORTS N FITNESS

33. Anaerobic Threshold The anaerobic threshold (AT) is reached when exercise intensity increases above steady-state aerobic metabolism and anaerobic production of ATP occurs. When the AT is crossed, exercise can only be sustained for a few minutes before hyperventilation begins to occur. Lactate accumulates progressively in the blood and the oxygen deficit and corresponding EPOC are extremely high. At this point, the body attempts to rid excess CO 2 (a by-product of acid metabolites). The increase in respiration is called the second ventilatory threshold (VT2). VT2 is an indirect indicator of AT. BFY SPORTS N FITNESS

34. Chronic Training Adaptations to Exercise SAID principle (specific adaptation to imposed demands) Examples include: Improved cardiac output efficiency (increased SV and lower HR) (aerobic training) Increase in respiratory capacity (aerobic training) Increase in maximal oxygen consumption (aerobic training) Increase in bone density (weightbearing exercise) Improved control of blood glucose and lipids (physical activity) Maintained or improved lean body mass (weightbearing activity) Decreased depression and anxiety (physical activity) Higher quality of life (physical activity) BFY SPORTS N FITNESS

35. Overtraining Overtraining often occurs during periods of intense overload in which signs and symptoms are individualized and include a combination of both physiological and emotional factors. Some signs and symptoms include: A decline in physical performance with continued training Elevated heart rate and blood lactate levels at a fixed submaximal work rate Weight loss Sleep disturbance Multiple colds or sore throats Irritability, restlessness, excitability, and/or anxiousness Loss of motivation and vigor Lack of mental concentration and focus Lack of appreciation for things that are normally enjoyable The best way to prevent overtraining is periodization. BFY SPORTS N FITNESS

36. Delayed Onset Muscle Soreness (DOMS) Research suggests DOMS is caused by tissue injury from excessive mechanical force, particularly eccentric force, exerted on muscle and connective tissue. Generally appears 24–48 hours after strenuous exercise Is thought to result from a series of events activated by strenuous exercise: First, structural damage occurs as a result of strenuous eccentric muscle actions. As a result, calcium is leaked out of the sarcoplasmic reticulum and collects in the mitochondria, halting ATP production. The build-up of calcium activates enzymes that break down proteins. The breakdown of proteins causes an inflammatory process. Lastly, the accumulation of histamines, potassium, prostaglandins and edema stimulates pain receptors, leading to the sensation of DOMS. Attempt to reduce DOMS by starting at a low intensity and progressing slowly through the first few weeks while minimizing eccentric actions. BFY SPORTS N FITNESS

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