C H A P T E R 6

1. C H A P T E R 6 METABOLIC ADAPTATIONSTO TRAINING

2. Learning Objectives w Find out how training can maximize the capacity of our energy systems and our potential to perform. w Learn the different muscle adaptations that occur with aerobic and anaerobic training. w Find out how specific types of aerobic and anaerobic training can improve performance. w Discover the best way to monitor changes in training.

3. Training Effects on the Skeletal Muscles Aerobic (endurance) training leads to w Improved muscle blood flow, and w Increased capacity of muscle fibers to generate ATP through oxidative metabolism. Anaerobic training leads to w Increased muscular strength and power, and w Increased tolerance for high acid production (low pH) through increased buffering capacity.

4. Individuality of Responses to Aerobic Training of Families and Individuals Twenty weeks of training: bars are families; points within bars are individual family members

5. . w Improved submaximal aerobic endurance and VO2max Adaptations to Aerobic Training w Ultimately, the magnitude of these changes depends on genetic factors

6. w Increased number of capillaries around the muscle fibers, which facilitates a greater delivery of oxygen . Muscular Adaptations w Increased cross-sectional area of ST fibers w Conversion of FTb to FTa fibers; there may be a small conversion of FT to ST fibers – this is controversial w Increased myoglobin content in the muscle fibers, which allows muscle to store more oxygen and facilitates oxygen diffusion within the fiber to the mitochondria (think seals and whales!) w Increased density of mitochondria in the fibers, and therefore, an increased oxidative enzyme activity

7. CAPILLARIZATION IN MUSCLES Untrained Trained

8. Training Effects on VO2max and SDH Activity (Krebs Cycle Enzyme) Note the difference in % increases in VO2max and SDH activity: this argues against muscle oxidative capacity limiting VO2max.

9. LEG MUSCLE ENZYME ACTIVITIES

10. Adaptations Affecting Energy Sources w Trained muscles store more glycogen and triglycerides than untrained muscles. w FFAs are better mobilized from muscle and fat cells and more accessible to trained muscles. Increased muscle store of fat Increased delivery because of increased muscle blood flow wMuscles’ ability to oxidize fat increases with training!! wMuscles’ reliance on fat stores conserves glycogen during prolonged exercise!!

11. MITOCHONDRIA (A), GLYCOGEN (B), AND TRIGLYCERIDES (C)

12. Adaptations to Aerobic Training w Increased fat availability and capacity to oxidize fat lead to increased use of fat as an energy source, which spares glycogen. This is one of the primary metabolic changes that occurs with aerobic training.

13. USE OF ENERGY SOURCES WITH INCREASING INTENSITY

14. . . QO2max vs VO2max . QO2max measures the maximal respiratory or oxidative capacity of muscle. . VO2max measures the body's maximal oxygen uptake.

15. . . QO2max and VO2max with Training

16. . Muscle oxygen consumption • At rest, about 20% of the oxygen consumption (~0.35 l/min) of the body is by the muscles (which make up ~ 40-45% of the body weight) • During maximal exercise, about 90% of the oxygen consumption (~3.5 l/min in a normally active person, ~7 l/min is the highest recorded) of the body is by the muscles

17. Volume w Frequency of exercise bouts w Duration of each exercise bout Intensity – energy cost per unit time of exercise w Interval training w Continuous training Aerobic Training Considerations

18. w Athletes who train with progressively greater volumes eventually reach a maximal level of improvement beyond which additional training volume will not improve endurance or VO2max (reach their genetic potential?). . Training Volume w Volume is the load of training in each training session (duration) and over a given period of time (frequency). w Adaptations to given volumes vary from individual to individual. w An ideal aerobic training volume appears to be equivalent to an energy expenditure of about 5,000 to 6,000 kcal per week.

19. Training Intensity: Power Output/Time w Muscular adaptations are specific to the intensity as well as the volume of training. wAthletes who incorporate high-intensity speed training show more performance improvements than athletes who perform only long, slow, low-intensity training (high volume). w Aerobic intervals are repeated, fast-paced, exercise bouts followed by short rests – interval training is usually most effective. w Continuous training involves one continuous, high-intensity exercise bout – because of fatigue, generally not as effective as interval training.

20. Adaptations to Anaerobic Training w Increased muscular strength and power* w Slightly increased creatine kinase and glycoytic enzymes; small increases in [ATP] and [PCr]; changes in muscle enzyme activity depend on type of training. w Improved mechanical efficiency w Increased muscle oxidative capacity (for sprints longer than 30 s) w Increased muscle buffering capacity*

21. Performance in a 60-S Power Test Before and After Anaerobic Training Thus, training increased power, but not fatigue resistance.

22. . w Repeated measurements of VO2max Methods of Monitoring Training Changes w Lactate threshold tests w Comparing lactate values taken after steady-state exercise at various times in the training period

23. CHANGES IN LACTATE THRESHOLD WITH TRAINING

24. Determining training progress The most practical and simplest protocol for monitoring training appears to be comparing single blood lactate values taken after a fixed-pace activity at various times during a training period. As you become better trained, your blood lactate concentration is lower for the same rate of work.

25. TRAINING AND BLOOD LACTATE CONCENTRATION (fixed level of work)

26. Anaerobic Training Performance improvements after anaerobic training (short, high-intensity training) appear to be related more to muscular strength gains than improvements in the anaerobic yield of ATP through the ATP-PCr and glycolytic systems.

27. Muscle Buffering Capacity w Anaerobic training improves muscle buffering capacity, but aerobic training does little to increase the muscles' capacity to tolerate sprint-type activities. w Improved muscle buffering capacity allows sprint-trained athletes to generate energy for longer periods before fatigue limits the contractile process.

28. Selected Muscle Enzyme Activities (mmol g min ) for Untrained, Anaerobically Trained, and Aerobically Trained Men . . -1 -1 Anaerobically Aerobically Untrained trained trained Aerobic enzymesOxidative systemSuccinate dehydrogenase 8.1 8.0 20.8Malate dehydrogenase 45.5 46.0 65.5Carnitine palmityl transferase 1.5 1.5 2.3 Anaerobic enzymesATP-PCr systemCreatine kinase 609.0 702.0 589.0Myokinase 309.0 350.0 297.0Glycolytic systemPhosphorylase 5.3 5.8 3.7Phosphofructokinase 19.9 29.2 18.9Lactate dehydrogenase 766.0 811.0 621.0 a a a a a a a a Denotes a significant difference from the untrained value.