Endocrine Responses to Resistance Exercise

1. Endocrine Responses to Resistance Exercise chapter3 Endocrine Responses to Resistance Exercise William J. Kraemer, PhD, CSCS, FACSM, FISSN, FNSCAJakob L. Vingren, PhD, CSCSBarry A. Spiering, PhD, CSCS

2. Chapter Objectives • Understand basic concepts of endocrinology. • Explain the physiological roles of anabolic hormones. • Describe hormonal responses to resistance exercise. • Develop training programs that demonstrate an understanding of human endocrine responses.

3. Key Point • It has been theorized that the endocrine system can be manipulated naturally with resistance training to enhance the devel-opment of various target tissues, thereby improving performance.

4. Section Outline • Synthesis, Storage, and Secretion of Hormones

5. Key Term • hormones: Chemical messengers that are synthesized, stored, and released into the blood by endocrine glands and certain other cells.

6. Glands of the Body • Figure 3.1 (next slide) • The principal endocrine glands of the body along with other glands that secrete hormones

7. Figure 3.1

8. Section Outline • Muscle as the Target for Hormone Interactions

9. Muscle Cell • Figure 3.2 (next slide) • The muscle cell is a multinucleated cell in which each nucleus controls a region of the muscle protein (called a nuclear domain).

10. Figure 3.2

11. Section Outline • Role of Receptors in Mediating Hormonal Changes

12. Lock-and-Key Theoryfor Hormonal Action • Figure 3.3 (next slide) • A schematic representation of the classic lock-and-key theory for hormonal action at the cell receptor level

13. Figure 3.3

14. Androgen Receptor Diagram • Figure 3.4 (next slide) • Diagram of a typical androgen receptor on the DNA element in the nucleus

15. Figure 3.4

16. Section Outline • Steroid Hormones Versus Polypeptide Hormones • Steroid Hormone Interactions • Polypeptide Hormone Interactions

17. Steroid Hormones VersusPolypeptide Hormones • There are two main categories of hormones: • Steroid • Polypeptide (or simply peptide)

18. Hormone Structure • Figure 3.5 (next two slides) • Structure of • (a) a polypeptide hormone (growth hormone, 22 kDa) • (b) a steroid hormone (testosterone)

19. Figure 3.5a

20. Figure 3.5b

21. Steroid Hormones Versus Polypeptide Hormones • Steroid Hormone Interactions • A steroid hormone passively diffuses across the sarcolemma of a muscle fiber. • It binds with its receptor to form a hormone-receptor complex (H-RC). • H-RC arrives at the genetic material in the cell’s nucleus and “opens” it in order to expose tran-scriptional units that code for the synthesis of specific proteins. (continued)

22. Steroid Hormones Versus Polypeptide Hormones • Steroid Hormone Interactions (continued) • RNA polymerase II binds to the promoter that is associated with the specific upstream regulatory elements for the H-RC. • RNA polymerase II transcribes the gene by coding for the protein dictated by the steroid hormone. • Messenger RNA (mRNA) is processed and moves into the sarcoplasm of the cell, where it is translated into protein.

23. Steroid Migration • Figure 3.6 (next slide) • The slide shows typical steroid migration into a target cell by either testosterone in skeletal muscle or dihydrotestosterone in sex-linked tissues. • Only one hormone pathway (testosterone or dihydrotestosterone) is targeted for one cell, butthe two are shown together in this diagram.

24. Figure 3.6

25. Steroid Hormones Versus Polypeptide Hormones • Polypeptide Hormone Interactions • Cyclic adenosine monophosphate-dependent (cyclic AMP-dependent) signaling pathway • Cytokine-activated JAK/STAT signaling pathway • Prototypical growth factor, mitogen-activated signaling pathway

26. Polypeptide Hormone Interaction • Figure 3.7 (next slide) • The slide shows typical polypeptide hormone (growth hormone in this example) interaction with a receptor via the cytokine-activated JAK/STAT signaling pathway. • Although the hormone binds to an external receptor, a secondary messenger (STAT) is activated that can enter the cell nucleus. • Tyr-P = tyrosinase related protein

27. Figure 3.7

28. Section Outline • Heavy Resistance Exercise and Hormonal Increases

29. Key Point • The specific force produced in activated fibers stimulates receptor and membrane sensitivities to anabolic factors, including hormones, which lead to muscle growth and strength changes.

30. Section Outline • Mechanisms of Hormonal Interactions

31. Mechanisms of Hormonal Interactions • Interactions with receptors are greater when • exercise acutely increases the blood concentrations of hormones. • Receptors are less sensitive when • the physiological function to be affected is already close to a genetic maximum, • resting hormone levels are chronically elevated due to disease or exogenous drug use, and • mistakes are made in exercise prescriptions.

32. Section Outline • Hormonal Changes in Peripheral Blood

33. Hormonal Changes in Peripheral Blood • Mechanisms contributing to changes in peripheral blood concentrations of hormones: • Fluid volume shifts • Tissue clearance rates • Hormonal degradation • Venous pooling of blood • Interactions with binding proteins in the blood • These mechanisms interact to produce certain concentrations of hormones in the blood, which influences the potential for interaction with receptors.

34. Key Point • Hormone responses are tightly linked to the characteristics of the resistance exercise protocol.

35. Section Outline • Adaptations in the Endocrine System

36. Adaptations in the Endocrine System • Examples of the potential types of adaptation with resistance exercise: • Amount of synthesis and storage of hormones • Transport of hormones via binding proteins • Time needed for the clearance of hormones through liver and other tissues • Amount of hormonal degradation that takes place over a given period of time • How much blood-to-tissue fluid shift occurs with exercise stress • How many receptors are in the tissue

37. Section Outline • Primary Anabolic Hormones • Testosterone • Free Testosterone and Sex Hormone–Binding Globulin • Testosterone Responses in Women • Training Adaptations of Testosterone • Growth Hormone • Efficacy of Pharmacological Growth Hormone • Growth Hormone Responses to Stress • Growth Hormone Responses in Women • Training Adaptations of Growth Hormone (continued)

38. Section Outline (continued) • Primary Anabolic Hormones • Insulin-Like Growth Factors • Exercise Responses of Insulin-Like Growth Factors • Training Adaptations of Insulin-Like Growth Factors

39. Primary Anabolic Hormones • There are three primary hormones involved in muscle tissue growth and remodeling: • Testosterone • Growth hormone (GH) • Insulin-like growth factors (IGFs)

40. Primary Anabolic Hormones • Testosterone • The primary androgen hormone that interacts with skeletal muscle tissue • Effects on muscle tissue: GH responses that lead to protein synthesis, increased strength and size of skeletal muscle, increased force production potential and muscle mass • Diurnal variations • Men: Exercise later in the day is more effective for increasing overall testosterone concentrations over an entire day. • Women: There are lower concentrations and little variation during the day.

41. Biosynthesis of TestosteroneFrom Cholesterol • Figure 3.8 (next slide) • The series of chemical reactions in the biosynthesis of testosterone from cholesterol

42. Figure 3.8

43. Key Point • Large muscle group exercises result in acute increased serum total testosterone concentrations in men.

44. Primary Anabolic Hormones • Testosterone • Free Testosterone and Sex Hormone–Binding Globulin • A higher total (bound) testosterone level allows for the potential of more free testosterone. • The free hormone hypothesis states that only the free hormone interacts with target tissues. • Testosterone Responses in Women • Women have 15- to 20-fold lower concentrations of testosterone than men do, and if acute increases occur after a resistance training workout, they are small. • Training Adaptations of Testosterone

45. Serum TestosteroneResponses to Exercise • Figure 3.9 (next slide) • Male (green bars) and female (gold bars) serum testosterone responses to two exercise programs: • (a) a protocol entailing eight exercises using 5RM and 3-minute rest periods between sets and exercises • (b) a program that called for eight exercises using 10RM and 1-minute rest periods between sets and exercises(the total work for the second protocol was higher) • * = significantly above preexercise levels • + = significantly above the other group

46. Figure 3.9 Reprinted, by permission, from Kraemer et al., 1990.

47. Primary Anabolic Hormones • Growth Hormone • Secreted by the pituitary gland • Interacts directly with target tissues, which include bone, immune cells, skeletal muscle, fat cells, and liver tissue • Regulated by neuroendocrine feedback mechanisms and mediated by secondary hormones • GH release patterns altered by age, gender, sleep, nutrition, alcohol consumption, and exercise

48. Growth Hormone Cybernetics and Interactions • Figure 3.10 (next slide) • Diagram of growth hormone cybernetics and interactions

49. Figure 3.10

50. Primary Anabolic Hormones • Growth Hormone • Efficacy of Pharmacological Growth Hormone • Pharmacological use of GH has unknown and unpredictable results. • Growth Hormone Responses to Stress • GH responds to exercise stressors, including resistance exercise. • GH response depends on load, rest, and volume of exercise.