C H A P T E R 3

1. C H A P T E R 3 NEUROMUSCULAR ADAPTATIONS TO RESISTANCE TRAINING

2. w Note changes in the muscle structure and in the neural mechanisms controlling the muscle that occur during resistance training. (continued) Learning Objectives w Learn the differences among the terms muscular strength, power, and endurance. w Examine how strength is gained through resistance training.

3. Learning Objectives w Learn what causes muscle soreness and how to prevent it. w Discover how to design and tailor a resistance training program to the specific needs of an individual. w Find out if there are strength training differences between women and men and between younger and older persons.

4. Homeostasis and Steady State Homeostasis: maintenance of a constant, unchanging internal environment by the physiological systems; normally only possible at rest; typically operate by negative feedback Powers and Howley, Exercise Physiology, 2004

5. Homeostasis and Steady State Steady State: a constant internal environment that may be different than rest, for example during steady state exercise Powers and Howley, Exercise Physiology, 2004

6. Acute Responses vs. Chronic Adaptations Acute responses to training involve how the body responds to one bout of exercise (for example, the increase in heart rate). Chronic physiological adaptations to training mark how the body responds over time to the stress of repeated exercise bouts (for example, the decrease in resting heart rate). 12 Week Training Before After After Before Before After

7. Defining Muscular Performance Strength—the maximal force a muscle or muscle group can generate (1RM) Power—the product of strength and the speed of movement. Key component of athletic performances. Muscular endurance—the capacity to sustain repeated muscle actions. Affected by strength, metabolic & circulatory capacity

8. Muscular Strength, Power, & Endurance wBench Press 1RM: wPower Test @ 1RM: wEndurance Test @ 75% of 1RM:

9. Selecting the Appropriate Resistance Strength—fewer reps and high resistance(<6RM); long rest Muscular endurance—many reps and low resistance (>20RM); short rest Muscle size— >3 sets; 6~12RM; short rest periods (<90s) Power— <5 reps w/ varying intensity over time (1~5RM or 6~10RM); ; emphasizing speed of movement

10. Dramatic effects of strength training Resistance training programs can produce a 25% to 100% improvement in strength within 3 to 6 months, irrespective of age or gender.

11. Results of Resistance Training on Muscle Strength in Males w Alterations of neural control of trained muscle. w Increased muscle size (hypertrophy).

12. Neural Adaptations w Synchronization and recruitment of additional motor units • Decreased neural inhibition; e.g., decreased GTO effects w Decreased co-activation of antagonist muscles w Increased rate coding (increased firing frequency of active motor units) Mechanisms of Gains in Muscle Strength Muscle Hypertrophy

13. Muscle Size wHypertrophy refers to increases in muscle size. wAtrophy refers to decreases in muscle size. • Although muscle strength involves more than just muscle size, in general strength is directly related to the cross-sectional area of the muscle or muscle group (specific force, e.g., kg force/cm2).

14. Muscle Size

15. A significant body of literature now shows: Resistance training can benefit almost everyone, regardless of his or her sex, age, level of athletic involvement, or sport.

16. Muscle Hypertrophy Transient—pumping up of muscle during a single exercise bout due to “squeezing” of fluid from the blood plasma into the interstitial spaces of the muscle because of high muscle pressures. Chronic—increase of muscle size after long-term resistance training due to changes in muscle fiber number (fiber hyperplasia) or muscle fiber size (fiber hypertrophy).

17. Muscle Fiber Hypertrophy w The numbers of myofibrils(thick and thin filaments) increase, so there are more cross-bridges in the cross-section of muscle, and hence, greater strength. wProtein turnover is continuous in the muscle; during hypertrophy, muscle protein synthesis increases more than proteindegradation during the post-exercise period. wTestosterone plays a role in promoting muscle growth. w Training at higher intensities, i.e., performing lower reps with higher loads, appears to cause greater fiber hypertrophy than training at lower intensities.

18. FIBER HYPERTROPHY AFTER TRAINING

19. Muscle Fiber Hyperplasia w Muscle fibers may split with intense weight training. w Each half may then increase in size. w Hyperplasia has been shown to occur in some experimental animal models; it has not been clearly demonstrated in human subjects. Quail and chicken: hanging a weight on the wing – hyperplasia of the latissimus muscles Cat: pulling a lever to obtain food – hyperplasia of the wrist flexor muscles

20. SPLITTING MUSCLE FIBER

21. Are Muscle Fiber Type Alterations Possible? Type FTb (IIb) fibers are converted to type FTa (IIa) with resistance training. There is recent evidence that some conversion from ST to FTa may occur with a combination of resistance training and short-interval speed work..

22. Protein Synthesis wDNA stores the information required for making all of the proteins needed by a cell wGene: segment of DNA that carries instructions about how to make specific proteins wNucleotide: Adenine, Guanine, Thymine, Cytosine, Uracil wChromosome: condensed form of DNA wProtein wAmino Acid: Alanine, Arginine, Glutamine, etc.

23. Protein Synthesis • *Transcription Belk & Borden, Biology, Pearson Prentice Hall, 2004

24. Protein Synthesis • *Transcription Belk & Borden, Biology, Pearson Prentice Hall, 2004

25. Protein Synthesis • *Transcription Belk & Borden, Biology, Pearson Prentice Hall, 2004

26. Protein Synthesis • *Transcription Belk & Borden, Biology, Pearson Prentice Hall, 2004

27. Protein Synthesis • *Transcription Belk & Borden, Biology, Pearson Prentice Hall, 2004

28. Protein Synthesis • * Translation Belk & Borden, Biology, Pearson Prentice Hall, 2004

29. Protein Synthesis • * Translation Belk & Borden, Biology, Pearson Prentice Hall, 2004

30. Protein Synthesis • * Translation Belk & Borden, Biology, Pearson Prentice Hall, 2004

31. Protein Synthesis • * Translation Belk & Borden, Biology, Pearson Prentice Hall, 2004

32. Protein Synthesis • * Translation Belk & Borden, Biology, Pearson Prentice Hall, 2004

33. Muscle Protein Degradation • ATP-dependent • - Proteosome • - Proteins are tagged by Ubiquitins, then degraded by proteosomes • ATP-independent • - Lysosome • - Calpain

34. Muscle Response to Exercise • Rates of muscle protein synthesis (RPS) are suppressed during resistance exercise. • Endurance Exercise leads to no appreciable change in muscle protein synthesis, while RPS is elevated after Resistance Exercise (6~48 h post RE).

35. Muscle Response to Training • Endurance Training (high frequency low-force output) • No appreciable change in muscle mass • Proliferation of mitochondria • Higher capillary density and blood flow to exercising muscle • Resistance Training (low frequency high-force output) • Elevated cross-sectional area in trained muscle • No change in mitochondrial volume • No change in number of capillaries • Onset of training results in strength gains that are not accompanied by changes in muscle CSA – enhanced efficiency for motor unit activation and effective use of muscle mass

36. Muscle Response to Training Rates of mixed gastrocnemius muscle protein synthesis after 5 weeks of resistance exercise

37. Satellite Cells Satellite cells are “adult stem cells” that are available to maintain a relatively constant nucleus to muscle mass ratio. Brooks, Fahey, & Baldwin, Exercise Physiology, McGraw-Hill, 2005

38. SATELLITE CELL Morgan and Partridge, Int J Biochem Cell Biol. 2003

39. SATELLITE CELL Hawke, Exerc Sport Sci Rev 33: 63, 2005

40. SATELLITE CELL Morgan and Partridge, Int J Biochem Cell Biol. 2003

41. Acute Muscle Soreness w Probably results froman accumulation of water (edema) or waste products in the muscles (e.g., lactic acid) w Usually disappears within minutes after exercise, with no lasting effects This may be experienced, for example, after a hard bout of uphill running, stair climbing, or other concentric exercise.

42. Delayed-Onset Muscle Soreness (DOMS) w Results primarily from eccentric contractions w Is associated with damage or injury to muscle fibers w Probably is caused by inflammation in the damaged muscles w May be due to edema (associated with the inflammation) in the muscle compartment w Is felt 12 to 48 hours after a strenuous bout of exercise, and may last up to a week First paper to use the acronym, “DOMS” - Armstrong, RB. Med Sci Sports Exerc 16: 529, 1984

43. Muscle before and immediately after running a marathon Disrupted sarcomeres

44. Muscle Fibers Immediately after a Marathon

45. Exercise-induced muscle injury Inflammation 2 days after downhill running Normal Inflamed

46. Armstrong’s Sequence of Events in DOMS 1. Structural damage to muscle fibers from high forces 2. Impaired calcium homeostasis resulting in necrosis 3. Inflammation: macrophage invasion of the damaged tissue 4. Accumulation of irritants that stimulate nociceptors within muscle

47. Muscle Injury and Performance w Injury causes a reduction in the force-generating capacity of muscles due to 1. physical disruption of the muscle, 2. failure in the excitation-contraction coupling process, and 3. loss of contractile protein w Maximal force-generating capacity returns after weeks w Muscle glycogen synthesis is impaired

48. Reducing Muscle Injury w Reduce eccentric component of muscle action during early training w Start training at a low intensity, increasing gradually or w Begin with a high-intensity, exhaustive bout of eccentric-action exercise to cause much soreness initially, but decrease future pain Over-the-counter anti-inflammatory drugs (e.g., aspirin) have not been shown to be effective in alleviating DOMS, although there is some disagreement on this issue.

49. Exercise-Induced Muscle Cramps wMay be due to fluid or electrolyte imbalances and/or sustained alpha-motoneuron activity from increased muscle spindle activity and/or decreased Golgi tendon organ activity. w Rest, passive stretching, and holding the muscle in the stretched position can be effective treatments w Proper conditioning, stretching, and nutrition are possible prevention strategies.