1. Part III Exercise Physiology 1

2. The study of the body’s immediate and long- term responses to exercise Useful for... See table on p. 120 Generally, evaluating fitness programs, designing effective fitness regimes, and assessing individual fitness in a vast array of applications It’s purpose is simply to understand everything there is to know about exercise 2

3. Chapter 10 Basic concepts of exercise metabolism 3

4. Objective from syllabus To summarize basic concepts of exercise metabolism The idea here is that, in order to understand how we can exercise, we must understand the body’s capacity to do work (i.e. produce energy) 4

5. Exercise metabolism Production of energy for exercise What do you know about energy limits for exercise? Could you sprint a mile with the right kind of training? 5

6. Exercise metabolism Production of energy for exercise Production of ATP Energy supply Muscles do work Work requires energy How does work done (energy cost) differ across different exercises? How does sprinting 100 yards differ from walking it? From jogging it? Our job is to understand the basic properties and capabilities of energy supply 6

7. Exercise metabolism Production of energy for exercise Production of ATP (adenosine triphosphate) ATP is the basic worker of the body It is the source of energy that allows muscles to contract (without muscle contraction you have no movement) It provides the energy by breaking down into ADP and phosphate While exercising, continued work is possible provided ADP and phosphate is reconstituted fast enough to provide enough ATP for the work done This reconstitution of ATP itself requires chemical energy, supplied by one of three different systems 7

8. Exercise metabolism Production of energy for exercise Production of ATP (adenosine triphosphate) 3 systems: (Differ according to the intensity of work they support – that is, the units of ATP per second they can reconstitute) The immediate energy system The anaerobic glycolytic system The oxidative system See table on p. 124 (good summary) 8

9. Exercise metabolism Production of energy for exercise The immediate energy system Relies on stores of phosphocreatine (PCr) to resynthesize ADP & phosphate into ATP Resynthesizes more ATP per unit time than any other system, but has a finite capacity – PCr runs out Used at the start of all exercise, and for high intensity brief bursts of work Doesn’t get replenished until you’ve been at rest for about 6 minutes Creatine supplements – useful for repeated bouts of high intensity work (health cost?) 9

10. Exercise metabolism Production of energy for exercise The anaerobic glycolytic system Relies on glucose to resynthesize ADP & phosphate into ATP Is the major source of ATP for exercise lasting between 20s and 3min In a 30s sprint, this system provides 60-65% of the ATP Glucose comes mostly from muscle stores, some from blood Lactic acid is the byproduct of glycolysis ATP is produced via the Krebs cycle Glycogen boosting/loading – see later 10

11. Exercise metabolism Production of energy for exercise The oxidative system Relies on oxygen to resynthesize ADP & phosphate into ATP Is the major source of ATP for exercise lasting more than 3min Oxygen, of course, comes from breathing, hence when you use this system, you breath heavily, or you get into oxygen debt This is the system where VO2 max becomes important – anyone heard of that? (see later) ATP resynthesis by this system is slow relative to the others 11

12. Exercise metabolism Production of energy for exercise The 3 energy systems as a continuum All systems always function – it’s the extent to which each is relied upon that changes with the kind of work done Think about a marathon...when would each system be used? 12

13. Production of energy for exercise The 3 energy systems as a continuum 13 Exercise metabolism The energy system continuum: the relative contribution of each system to ATP resynthesis depends on exercise duration and intensity

14. Exercise metabolism Production of energy for exercise The fueling of ATP by fats, proteins, and carbohydrates Carbohydrate (glucose) – can be used to supply energy aerobically or anaerobically Fats (fatty acids) & proteins (amino acids) – can only be used to supply energy via oxidative system Relative use of fat (fatty acids) and carbohydrates (glucose): Rest, low intensity – each used equally Higher intensity – relies more on glucose (proteins - amino acids –used more only when glucose is in very short supply – e.g. sustained endurance exercise) 14

15. 15 fats proteins carbohydrates Carbon dioxide Lactic acid The un-reconstituted ADP &P i The reconstituted ATP, & water

16. Exercise metabolism Production of energy for exercise Lactic acid – friend or foe? Lactic acid accumulates as a consequence of glycolysis Concentration in muscles and blood can increase up to 15 x during max exercise (rowing example) Increases acidity of muscles & blood (LA  La + H -, & H - lowers pH of muscle/blood) [lower pH   acidity] Increased acidity slows anaerobic pathway This inhibits ATP production...= fatigue Protective, as excess acidity kills cells…self-regulation 16

17. Exercise metabolism Production of energy for exercise Lactic acid – friend or foe? Lactic acid is circulated to various body parts (heart, liver, other muscles) & oxidized (removed) both during and after exercise In muscle, its breakdown can be used to reconstitute ATP (providing further fuel for exercise) via oxidative pathway In the liver, after exercise, it can be used to form glucose, which is used to resynthesize glycogen lost during exercise 20-40 minutes to remove LA after exercise Removal is faster if still gently exercising (LA used as fuel to reconstitute ATP) Recovery exercise should be gentle – don’t want to create more LA 17

18. Exercise metabolism Oxygen supply during sustained exercise Aerobic system provides >50% ATP for exercise > 3 minutes, & 20-30% when exercise lasts 30-60s Whatever ATP cannot be supplied by aerobic system must be supplied anaerobically 18

19. Exercise metabolism Oxygen supply during sustained exercise VO 2 measures energy expenditure First few minutes – oxygen debt (energy supplied anaerobically – discomfort) then O 2 system kicks in (“second wind”) Constant exercise can result in plateau of V O 2 (steady state) – could go on forever… If intensity keeps rising, so does V O 2...until it reaches “V O 2 max” After exercise, oxygen continues to be used, to remove lactate, and resynthesize the various energy stores (called excess post exercise oxygen consumption - EPOC) 19

20. Exercise metabolism Oxygen supply during sustained exercise Summary of previous slide: 20

21. Exercise metabolism Oxygen supply during sustained exercise V O 2 max (aerobic power) as an indicator of endurance exercise capacity V O 2 max is...the maximum amount of oxygen that can be used to synthesize ATP – hence a measure of the highest intensity work you can manage without relying in addition on the finite energy supplies of the other two energy systems (to increase total possible energy supply) 21

22. Exercise metabolism Oxygen supply during sustained exercise V O 2 max (aerobic power) as an indicator of endurance exercise capacity V O 2 max responds to training, but is also partially genetically determined Be careful of simplistic statements here – the extent of genetic determination is a complex matter (c. 40%...used to be thought to be 90%!) Also, many other factors combine to determine who succeeds at high intensity aerobic events (Lance Armstrong did not succeed just because he has a huge V O 2 max...though he does) 22

23. Exercise metabolism Measurement of exercise capacity Aerobic or endurance exercise capacity V O 2 max measures aerobic power, but endurance exercise capacity measures capacity to perform prolonged aerobic exercise (not the maximum intensity) Specificity of exercise (running, bicycling, arm ergometers, rowing machines, etc...) V O 2 max – highest volume of O 2 (p/unit time) consumed during exercise – but the person will continue exercising for a while after reaching this – why? 23

24. Exercise metabolism Measurement of exercise capacity Anaerobic exercise capacity Anaerobic power (2-3s) E.g. Margaria-Kalamen step test Anaerobic capacity (30-60s) E.g. Wingate bike test (30s in my experience) Why measure exercise capacity? Measures training effectiveness Talent identification Exercise prescription (VO 2 max, heart rate, perceived exertion – see next slide) Different levels of VO 2 appropriate for different types of athlete (see ch. 11) 24

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26. Exercise metabolism The cardiorespiratory system and oxygen supply during exercise Cardiorespiratory system: Lungs, breathing tubes (trachea, bronchii, other tubes), heart & blood vessels Oxygen passed from air sacs in lungs (alveoli) to blood in capillaries surrounding these sacs Transfer v. rapid Blood goes from pulmonary veins to heart, then to arteries, then to capillaries It is this later stage of distribution and gas exchange that limits endurance performance 26

27. Exercise metabolism The cardiorespiratory system and oxygen supply during exercise Cardiovascular response to exercise HR & respiration increase prior to exercise in the trained person HR increases with work intensity (oxygen supply) Max HR estimate = 220 – age (very variable about this estimate (I can still get to 200 – shouldn’t be able to according to this) 27

28. Exercise metabolism The cardiorespiratory system and oxygen supply during exercise Cardiovascular response to exercise Stroke volume (amount of blood pumped per contraction of heart): increases with work intensity With training, SV continues to increase Cardiac output: Blood pumped p/minute Function of both SV and HR, naturally Increases linearly with increased work rate Minute ventilation (air brought into lungs): number of breaths, and their depth Blood flowing though lungs is full of oxygen, even when working maximally – so that’s not a cause of exhaustion (nasal strips not necessary) Though respiratory muscles may fatigue 28

29. MaximalSub-maximal Exercise metabolism The cardiorespiratory system and oxygen supply during exercise Distribution of blood flow during exercise At rest 29

30. Exercise metabolism Human skeletal muscle cells Human Skeletal Muscle Fiber Types CharacteristicSlow-twitch (ST)Fast twitch (FTa)Fast twitch (FTb) Fiber sizeSmallLarge Contraction SpeedSlowFast ForceLowHigh Glycolytic capacityLowHigh Oxidative capacityHighModerately highLow Capillary supplyHighModerately highLow Fatigue resistanceHighModerateLow 30

31. Exercise metabolism Human skeletal muscle cells Muscle fiber type and exercise capacity Activation of fiber types during exercise Fig 10.12 100 80 60 40 20 0 LightModerateMaximal % Muscle fibers used Muscular force ST fibers FTa fibers FTb fibers Note – this is not a diagram of the amount of force produced Use this idea in the design of training programs – which type of fiber do you need? 31

32. Exercise metabolism Human skeletal muscle cells Skeletal muscle “fiber typing” – muscle biopsy 32

33. Exercise metabolism Human skeletal muscle cells Importance of muscle fiber type to sport performance Many other sports activities do not rely exclusively on a particular fiber type 33

34. Exercise metabolism Energy cost of activity Factors implicated: Intensity Efficiency of technique Body mass (depending on whether activity is supported – for example, swimming and running differ greatly) Has implications for: the amount you need to eat to support training The number of calories you’ll burn performing an activity 34

35. Exercise metabolism Importance of diet to energy metabolism and exercise performance Why athletes need a high carbohydrate diet 200 150 100 50 0 50150250 Low Moderate High Exercise time to exhaustion Glycogen in muscle Energy released per liter of O 2 consumed SubstrateEnergy p/l of O 2 (kcal) Carbohydrate5.05 Fat4.70 Protein4.82 So, if you have more glycogen, you can exercise longer before exhaustion 35 So you get more energy p/l of O2 with carbs

36. Exercise metabolism Importance of diet to energy metabolism and exercise performance Do athletes need extra protein? No, provided they have a healthy diet (see table 10.5, p. 141) Having too much can be bad – excess is excreted through kidneys or laid down as fat – it does not get used to produce extra muscle Importance of replacing water lost during exercise 70-80% of work done is lost as heat Can sweat 1 and 6.3 pints p/hr! See recommendations on p.141 Note that for exercise of up to 1hr, recommendation is for plain water 1 hr+ of intense exercise brings a recommendation for sport drinks (w/glucose, electrolytes) 36

37. Michael Phelps’ Breakfast http://www.guardian.co.uk/lifeandstyle/wo rdofmouth/2008/aug/15/myattemptatmich aelphelpsb 37

38. Chapter 11 Physiological adaptations to training 38

39. Objective from syllabus To summarize how training can affect the capacity to perform work 39

40. Physiological adaptations to training Overall training goals: Outcomes are dependent on the program – must bear in mind the different energy systems Always need to work on muscular strength, power and endurance 40

41. Physiological adaptations to training Training-induced metabolic adaptations Start by estimating needs of activity to be trained for (in terms of energy system Examples Endurance training increases muscle glycogen stores Muscle PCr stores increase with power training and short sprint training Sweating increases in the trained person (starts earlier and increases in total volume – e.g.Craig Sharp, Seb Coe) 41

42. Physiological adaptations to training Training-induced metabolic adaptations Factors limiting exercise performance Power & Speed lasting a few seconds Muscle fiber (FT) recruitment, balance & coordination Brief high intensity (can be maintained < 1 min) ATP from PCr system primarily PCr depletion, “highish” lactate levels, chemical... Elite sprinters (100m-200m) use PCr to resynthesize ATP quicker than non-elite sprinters 42

43. Physiological adaptations to training Training-induced metabolic adaptations Factors limiting exercise performance Longer high intensity (1-7 minutes) 30s to 2-3 min PCr depletion, high lactate levels, chemical...see last bullet pt. ATP provided quickly, but limited by LA Electrolyte (potassium, sodium, calcium, etc…) distribution becomes an issue 3-10 min LA accumulation, glycogen depletion, electrolyte distribution 43

44. Physiological adaptations to training Training-induced metabolic adaptations Factors limiting exercise performance Prolonged moderate to high (10-40 min) Some lactate, some glycogen loss, dehydration, chemical... Very prolonged Glycogen loss, dehydration, increased body temperature, low blood glucose, amino acid ratio in blood Latter 2 highly involved in sensation of fatigue 44

45. Physiological adaptations to training Training-induced metabolic adaptations Factors limiting exercise performance Note that some (many) sports use combinations of all three systems, in different proportions, so training needs to reflect that Research attempts to specify what energy systems are used most in which sporting activities 45

46. Physiological adaptations to training Training-induced metabolic adaptations Immediate and anaerobic system changes after strength and sprint training Increased stores of PCr, ATP & glycogen in muscle (esp. FT) Increased ATP generated by anaerobic glycolysis (also higher levels of lactic acid, but increased capacity to tolerate it balances this out) Muscle fiber size increases, increased # cross bridges, more muscle fibers are activated, and chemical balance is maintained (allowing for better maintenance of electrical conductance & excitation) All changes lead to more power, of course See table on page 145 46

47. Physiological adaptations to training Training-induced metabolic adaptations Changes in aerobic metabolism after endurance training 6 weeks should increase VO2 max by 20% to 40%! Activity of enzymes in Krebs cycle increases by 100% +… See table on page 146 47

48. Physiological adaptations to training Training-induced metabolic adaptations Activity of enzymes in Krebs cycle increases by 100% +… See table on page 146 48

49. Physiological adaptations to training Training-induced metabolic adaptations Changes in aerobic metabolism after endurance training Summary of important changes… See table on page 146 49

50. Physiological adaptations to training Summary of important changes... AdaptationConsequence VO2 max  Duh... Muscle glycogen  work before fatigue Kreb’s cycle Enyzmes  use of oxygen Use of fats for fuel  Don’t use so much glycogen Lactic acid removal  work before fatigue Lactate threshold  work before fatigue # capillaries within muscle  Good stuff in, bad out Muscle oxygen extraction  O2 for ATP Muscle myoglobin  O2 transport in muscle 50 Iron containing protein – enhances O2 transport for metabolism

51. Physiological adaptations to training Endurance training-induced changes in the cardiorespiratory system Oxygen consumption Stays the same at rest or at moderate exercise It’s the max that increases Amount of adaptation with training depends on amount of training and whether you’re already close to your max 51

52. Physiological adaptations to training Endurance training-induced changes in the cardiorespiratory system Heart rate Normal = 60-70 bpm Endurance = 30-40 bpm (sometimes) Amount of blood pumped maintained by bigger stroke volume Stroke volume Increases both at rest and at work As intensity increases so stroke volume increases (in the trained person) 52

53. Physiological adaptations to training Endurance training-induced changes in the cardiorespiratory system Cardiac output Increases with alteration in stroke volume (only when exercising) Oxygen extraction Increased (muscles are able to extract more oxygen from blood during exercise) There’s also more blood available (see above) 53

54. Physiological adaptations to training Endurance training-induced changes in the cardiorespiratory system Blood composition Less viscous, more oxygen carrying capacity, better thermoregulation Endurance training-induced respiratory changes More air breathed p/minute (adaptations in respiratory muscles) Better able to get rid of CO2, deplete lactic acid 54

55. Physiological adaptations to training Endurance training-induced changes in the cardiorespiratory system Endurance training induced changes in the lactate threshold Lactic acid production increases rapidly at a certain work intensity (= the LA threshold) Somewhere between 50% (untrained low) to 85% (trained high) of VO2 max Here’s the difference between trained/untrained It’s the max intensity that the aerobic system can manage without the anaerobic system contributing a large dose of the energy Actually a better measurement of max aerobic performance than VO2 max (important to measure in elite athletes) The intensity that can be maintained without fatigue (theoretically) 55

56. Physiological adaptations to training Muscular system changes after strength training Muscular fitness Strength, power, endurance Muscular strength Can increase for a variety of causes (neural, structural, metabolic) Contribution may vary across individuals (20% to 100% over several months) Training specificity is still relevant (if you want maximum strength gains, must train the 1-3 rep max occasionally (largest FTb fibers only recruited at 70% of max or greater) 56

57. Physiological adaptations to training Muscular system changes after strength training Muscular strength Muscle hypertrophy Starts after 6-8 weeks training Major cause of strength gain after this  muscle fiber size,  connective tissue between fibers Fiber size  because of  # of contractile filaments (more cross bridges that generate force) Protein synthesis , exceeds protein degradation (more protein in muscle) Hypertrophy will be specific to the muscle fibers trained (if you want hypertrophy in all fibers, vary resistance and increase training time...but that means longer sessions, more problems with fatigue...wait, I’ll take some supplements...you can see how it goes) Largest fibers are FTb, and they are also the strongest, so they are the ones to target for big muscles (big loads - grunt) 57

58. Physiological adaptations to training Muscular system changes after strength training Muscular strength Metabolic adaptations ATP, PCr & glycogen content of muscle  Enzyme activity  (  PCr brkdown, ATP production) Increases capacity for brief powerful contractions Neural adaptations 1-8 weeks Better synchronicity of motor unit recruitment, less neural inhibition…real neural level adaptations Reduced antagonist muscle activation, increased synergist muscle activation, and of course better coordination 58

59. Physiological adaptations to training Muscular system changes after strength training Muscular power and endurance Power = strength (greater force) with speed Faster contractions have less potential force, and vice versa (at any one point – clearly to move a 10lb weight quicker requires more force) Max power occurs at something like 30-50% max force How you train (speed/strength) is directly linked to the training effect...specificity of training Endurance increases with strength – the stronger you are, the less %MVC you need to use for any given contraction, so you can maintain it for longer (same total submax force can be achieved w/fewer motor units) 59

60. Physiological adaptations to training Muscular system changes after strength training Training and muscle fiber number or type Fiber type largely genetically determined  in # fibers possible, but unlikely to contribute much to strength change compared to hypertrophy and neural adaptation Alteration from FTb to FTa also possible (though very difficult) – but can be reversed when training stops  oxidative capacity, capillary #...endurance No evidence of alteration from ST to FT 60 Now questioned (see for example Ericsson 2004)

61. Physiological adaptations to training Basic principles of training Specificity Match the speed, force, and timing of the target activity Training variables Mode, duration, intensity and frequency...all can be varied Training for health will differ greatly from training for sport Overload Manipulate training variables across workouts to ensure muscles worked to capacity 61 e.g. Steve Cram e.g. Surgeon general’s recommendation, ACSM

62. Physiological adaptations to training Basic principles of training Individualization Tailor training to suit your own needs...we’re all a little different Reversibility Unless you keep exercising you will lose the adaptations caused by becoming fit (detraining is rapid) Training to maintain fitness does not have to be as rigorous as that required to cause it (50% reduction in training ok for 2-3 weeks…little loss of fitness) Periodization Little peaks, followed by plateaus, followed by changes in intensity or other training variables, followed by increased peaks, and so on... Microcycles (1-2 weeks) and macrocycles (2 weeks – 2 months) Training is planned around peaking at the right time 62

63. Physiological adaptations to training Basic principles of training Overtraining Too much of a good thing...can have serious consequences Fatigue, illness, injury Requires prolonged rest and less training – sometimes for several months Correct training requires both understanding the scientific principles, and observing the individual athlete to see whether it’s working for them. 63

64. Physiological adaptations to training Basic principles of training Continuous and interval training 64

65. Physiological adaptations to training Basic principles of training Continuous and interval training Continuous training Benefits vary (see table previous slide) Low intensity: 50-60% for non-athletes, 70-80% for athletes High intensity: 60% + for non-athlete, 85% + for athlete Can vary pace to avoid monotony, spread training benefits 65

66. Physiological adaptations to training Basic principles of training Continuous and interval training Interval training Often more beneficial than continuous (can work at greater intensity, causing greater adaptations – e.g. synchronous motor unit recruitment) 66

67. Physiological adaptations to training Training for cardiovascular endurance Healthy, young individual: To improve VO 2 max, exercise for at least 15min at 60% of VO 2 max or better, 3 x p/week or more Older, unfit, infirm: can still improve with less intensity ( low as 30-40% VO 2 max ) 67

68. Physiological adaptations to training Training for cardiovascular endurance Reliably improving fitness: 50-85% VO 2 max for 20-60m, 3-5 x p/wk Elite athlete: several hours a day at 85% or more of max (!) It’s a continuum – the fitter you are, the harder it is to gain further improvements 68

69. Physiological adaptations to training Methods of strength training Health stuff: strength training improves: glucose tolerance blood lipid levels body composition Strength training helps with: Back pain Osteoporosis Mobility Muscle tone 69

70. Physiological adaptations to training Methods of strength training Types of muscle contractions Static (isometric) & dynamic (concentric, eccentric) contractions can be used in training (static are rare) Types of strength training Isometric not good (gains specific to joint angle trained) Iso-inertial (isotonic – fixed resistance) & isokinetic (fixed speed, you maximize force [machine measures how much force you can produce moving at a given speed]) Remember training specificity Isotonic training most realistic and so gives most gains Isokinetic machines mostly used therapeutically 70

71. Physiological adaptations to training Methods of strength training Training to improve muscular strength and endurance and to induce hypertrophy # reps; # sets; # sets x # reps (total volume); resistance Express intensity as either an absolute (10RM) or relative weight (% 1RM) Power: hypertrophy first, then strength, then speed work To develop  RepsSetsIntensityRest between sets Max strength2-63—6High> 3 min Hypertrophy8-123-6Moderate> 3 min Endurance15-251-4Moderate< 1 min Power2-63-5Fast moving> 3 min HR fitness8-201-2Moderate< 1 min 71

72. Physiological adaptations to training Methods of strength training The role of eccentric muscle actions in strength training These are most problematic for injury/soreness, but seem to confer benefits in training effects too (why would this be a surprise?) Most normal exercises incorporate both concentric and eccentric contractions 72

73. Physiological adaptations to training Causes of muscle soreness Weakens muscle (sore muscle is weak muscle) Can be immediate... “Burning” in the muscle caused by LA build up – temporary (gone after a few hours) Or delayed... DOMS can last for several days (it’s the one that greets you when you wake up the next day, even two days later) Likely after eccentric work Once you’ve had it once, it becomes less likely to occur again (in that training regime) It does not seem to be a necessary part of training…though tissue damage is involved in strength gain 73

74. Physiological adaptations to training Exercise for health-related fitness ACSM and USSG exercise guideline summaries www.acsm.org/physicalactivity What should I do to stave off illness/CVD/stay healthy? Answer varies greatly from one individual to another See tables on p. 161 for summary Explaining the summaries Types of recommended exercise “large muscle groups” – walking, cycling, jogging – impact CVD risk factors, and less likely to be risky in terms of inflated blood pressure (as opposed to weight training) 74

75. Physiological adaptations to training Exercise for health-related fitness Explaining the summaries Intensity of exercise “moderate” – you get the training benefits but at less injury risk 50-70% for fat burn & health, 70-85% for fitness gain Duration of exercise 15+ min for health, less than 60 min to avoid injury Long duration low intensity for fat burn vice versa for… Frequency of exercise Less than 3 x per week – little gain in fitness, more than 5, greater risk of injury Low intensity exercise can be done every day (low injury risk) 75

76. Physiological adaptations to training Exercise for health-related fitness Resistance exercise Good for reduced risk of heart disease, osteoporosis, and increased functional capacity 76