1. Endocrine Responses to Resistance Exercise
chapter 3
Endocrine Responses to Resistance Exercise
William J. Kraemer, PhD, CSCS, FACSM, FISSN, FNSCA Jakob L. Vingren, PhD, CSCS Barry 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. Muscle Remodeling Involves:
Disruption and damage of muscle fibers
An inflammatory response
Involves immune system and various immune cells (T cells) which are under endocrine control
Hormonal interactions
Synthesis of new proteins and incorporation into existing or new sarcomeres

12. Muscle Remodeling
The increase in protein synthesis and decrease in protein degradation are first steps in muscle growth.
Type I depend more on a reduction of protein degradation
Type II depend on a dramatic increase in protein synthesis

13. Muscle Remodeling
Hormones are involved with protein synthesis and degradation mechanisms.
Anabolic hormones – promote tissue building
insulin, insulin-like growth factors, testosterone, growth hormone
Catabolic hormones – degrade cell proteins and support glucose synthesis
cortisol, progesterone

14. Section Outline Steroid Hormones Versus Polypeptide Hormones
Steroid Hormone Interactions
Polypeptide Hormone Interactions

15. Steroid Hormones Versus Polypeptide Hormones
There are two main categories of hormones:
Steroid
Polypeptide (or simply peptide)

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

17. Figure 3.5a

18. Figure 3.5b 18

19. 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)

20. 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.

21. 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, but the two are shown together in this diagram.

22. Figure 3.6

23. 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

24. 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

25. Figure 3.7

26. Section Outline
Heavy Resistance Exercise and Hormonal Increases

27. 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.

28. Section Outline
Mechanisms of Hormonal Interactions

29. 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.

30. Heavy Resistance Exercise and Hormonal Increases
Hormones are secreted during and after the resistance exercise
Due to physiological stress of the exercise
When forces are produced it requires the activation of high-threshold motor unites
Not typically stimulated by other types of exercise
Stress produces alterations in sarcolemma’s ability to import nutrients and in the sensitivity and # of hormone receptors

31. Heavy Resistance Exercise and Hormonal Increases
The extent of hormonal interactions in the growth of muscle fibers is dictated by loads and exercise angles used in training program
If use same exercise only specific set of muscle fibers will grow
Some fibers may be close to genetic ceilings for size
Volume of work, rest periods, and type of protocol are vital to hormonal changes

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

33. Section Outline Primary Anabolic Hormones Testosterone Growth Hormone
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)

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

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

36. Primary Anabolic Hormones
Testosterone
The primary androgen hormone that interacts with skeletal muscle tissue
Indirect effects on muscle tissue:
GH responses that lead to protein synthesis
Interact with receptors on neurons which can increase the amounts of neurotransmitters and influence protein changes
Direct effects on muscle tissue:
Gets into cell and binds to nuclear androgen receptor which binds to DNA and causes in increase in DNA transcription – thus protein synthesis
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.

37. Key Point
Large muscle group exercises result in acute increased serum total testosterone concentrations in men.
Heavy resistance (85-95% of 1 RM)
Moderate to high volume achieved with multiple sets, multiple exercises or both
Short rest intervals (30 seconds to 1 min.)
Two years or more of resistance training experience.

38. Primary Anabolic Hormones
Testosterone
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
Training time and experience may be very important factors in altering resting and exercise-induced concentrations
Role in skeletal muscle may change as upper limits of muscle size are achieved
Resistance training increases the muscle androgen receptor content

39. Serum Testosterone Responses 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

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

41. 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

42. Physiological Roles of GH
Decrease glucose utilization and glyocogen synthesis
Increase AA transport across cell membrane
Increase protein synthesis
Increase utilization of fatty acids
Increases lipolysis
Increase availability of glucose and AA
Increases collagen synthesis

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

44. Figure 3.10

45. Primary Anabolic Hormones
Growth Hormone
Growth Hormone Responses to Stress
GH responds to exercise stressors, including resistance exercise.
Significant stimulus is hydrogen ion and lactate
GH response depends on load, rest, and volume of exercise.
Most significant increases with 1-minute rest with 10RM vs. 5 RM

46. Primary Anabolic Hormones
Growth Hormone
Growth Hormone Responses in Women
GH concentrations and responses to exercise vary with menstrual phase.
Women have higher blood levels of GH than do men.

47. Key Point
Growth hormone is important for the normal development of a child and appears to play a vital role in adapting to the stress of resistance training. However, GH injections result in a wide variety of secondary effects not related to changes in muscle size or strength and can, in fact, result in hyper-trophy with less force production than occurs with exercise-induced hypertrophy.

48. Primary Anabolic Hormones
Insulin-Like Growth Factors
Exercise Responses of Insulin-Like Growth Factors
Insulin-like growth factor I (IGF-I) is most studied because of its role in protein anabolism.
Exercise results in acute increases in blood levels of IGF-I.

49. Primary Anabolic Hormones
Insulin-Like Growth Factors
Training Adaptations of Insulin-Like Growth Factors
Changes in IGF-I appear to be based on the starting concentrations before training.
If basal concentrations are low, IGF-I increases.
If basal concentrations are high, there is no change or it decreases.

50. Section Outline The Adrenal Hormones Cortisol Catecholamines
Role of Cortisol
Resistance Exercise Responses of Cortisol
Catecholamines
Role of Catecholamines
Training Adaptations of Catecholamines

51. The Adrenal Hormones Cortisol Role of Cortisol
Catabolic effects
Converts amino acids to carbohydrates, increases the level of enzymes that break down proteins, and inhibits protein synthesis
Resistance Exercise Responses of Cortisol
Cortisol increases with resistance exercise.
Training may reduce the negative effects of this increase.
Vast differences are observed in the physiological role of cortisol in acute versus chronic responses.

52. Key Point
Resistance exercise protocols that use high volume, large muscle groups, and short rest periods result in increased serum cortisol values. Though chronic high levels of cortisol may have adverse catabolic effects, acute increases may contribute to the remodeling of muscle tissue.

53. The Adrenal Hormones Catecholamines Role of Catecholamines
Increase force production via central mechanisms and increased metabolic enzyme activity
Increase muscle contraction rate
Increase blood pressure
Increase energy availability
Increase blood flow
Augment secretion rates of other hormones, such as testosterone
Training Adaptations of Catecholamines

54. Key Point
Training protocols must be varied to allow the adrenal gland to engage in recovery processes and to prevent the secondary responses of cortisol, which can have negative effects on the immune system and protein structures.

55. How Can Athletes Manipulate the Endocrine System?
General Concepts
The more muscle fibers recruited for an exercise, the greater the extent of potential remodeling process in the whole muscle
Only muscle fibers recruited for an exercise are subject to adaptation, including hormonal adaptations to stress

56. How Can Athletes Manipulate the Endocrine System?
To Increase Testosterone Concentrations
Large muscle group exercises (e.g., deadlift, power cleans, squats)
Heavy resistance (85% to 95% of 1 RM)
Moderate to high volume of exercise, achieved with multiple sets or multiple exercises
Short rest intervals (30 – 60 seconds)

57. How Can Athletes Manipulate the Endocrine System?
To Increase Growth Hormone Levels
Use workouts with higher lactate concentrations and associated acid-base disruptions;
High intensity (10 RM or heavy resistance) with 3 sets of each exercise (high total work) and short (1 minute) rest periods
Supplement diet with carbohydrate and protein before and after workouts

58. How Can Athletes Manipulate the Endocrine System?
To Optimize Responses of Adrenal Hormones
Use high volume, large muscle groups, and short rest periods, but vary the protocol and the rest period length and volume to allow the adrenal gland to engage in recovery processes (secreting less cortisol) and to prevent chronic catabolic responses to cortisol. This way the stress of the exercise will not result in overuse or overtraining.