Endocrine Responses and Adaptations to Strength Training

1. Endocrine Responses and Adaptations to Strength Training Shin-Shan Lu, Ph.D. Dept. Exercise Health Science National Taiwan University of Physical Education and Sport

3. Hormones • Hormones are chemical messengers that are synthesized, stored in, and released into the blood • Hormones have specific receptors on target tissues • Many hormones exert their effects on multiple tissues throughout the body (i.e. skeletal muscle, neurons, liver cells, immune cells, etc.) • Hormones most commonly studied in the field of exercise science include Testosterone, Growth Hormone (GH), Insulin Growth Factor I (IGF-I), & Cortisol

4. Hormones • Anabolic Hormones–hormones that promote tissue building i.e. Testosterone, IGF-I, GH, insulin • Catabolic Hormones– hormones that promote protein degradation in attempt at glucose synthesis i.e. Cortisol • The increase in protein synthesis and decrease in protein degradation are the first steps in muscle growth • Type I fibers depend more on the reduction in protein degradation • Type II fibers depend on a dramatic increase in protein synthesis

5. Mechanism of Hormone Action

7. Muscular Remodeling • Following a training period, muscle remodeling occurs as a result of damage to the muscular fibers, an inflammatory response, hormonal interactions and ultimately the synthesis of new proteins (Actin & Myosin) and their orderly incorporation into existing sarcomeres • The most prominent resistance training adaptation in muscle is an increase in the amount of a muscle’s contractile proteins: Actin & Myosin

8. Myosin proteins can undergo a conversion in their molecular structure from Type IIb to Type Ia • Also occurring is an increase in the synthesis and deposition of non-contractile, structural proteins to maintain the integrity and orientation of the contractile proteins

9. Heavy Resistance Exercise & Hormonal Increases • Hormones are secreted during and after the resistance exercise bout due to the physiological stress of resistance exercise • Acute hormonal secretions provide information to the body regarding such things as • The amount and type of physiological stress • The metabolic demands of the exercise • The need for subsequent changes in resting metabolism • The patterns of stress and hormonal responses combine to shape the tissues' adaptive response to a specific training program

10. The specific force produced in the activated muscle fibers stimulates membrane receptors and ultimately makes the fiber more sensitive to anabolic hormones, leading to muscular and strength growth. • If the stress is too great, catabolic actions in the muscle may occur as a result of the inability of anabolic hormones to bind to receptors

11. Neuroendocrine system Responses to Heavy Exercise

12. The magnitude of the hormonal response depends on the amount of tissue stimulated & the amount of tissue remodeling and repair post exercise stress • Only muscle fibers that are activated by the resistance training are subject to adaptation; and only those fibers realize the benefits of the resistance training program

13. Factors Affects Training-Related Adaptation in the Neuroendocrine system

14. Testosterone • The primary hormone that interacts with skeletal muscle tissue • Testosterone interacts with both skeletal muscle and the motor neurons that supply them • Following high intensity aerobic endurance exercise and/or resistance training result in an increase in blood concentration of testosterone in men in particular, and to a much less degree, women

15. This same type of exercise program can cause an increase in catabolic hormones, so testosterone increases may be related to the need for protein synthesis to keep pace with the catabolic protein loss • Hypertrophy does not typically happen through aerobic endurance training; a decrease in muscle fiber size may be realized

16. Testosterone can be increased through: • Large muscle group exercises • Heavy resistance (85-95% 1RM) • Moderate to high volume of exercise, with multiple sets, multiple exercises or both • Short rest periods (30s – 1 minute) • 2 years or more of resistance training experience • Testosterone levels are typically highest for males in the morning; with women having 15-20x less testosterone with little daily variation

17. Factors Affecting Testosterone • The use of large muscle group exercise • The time course of blood sampling around an exercise protocol • The pre-exercise concentraction

18. Testosterone Response to Various Strength Exercise Protocol

19. Effects of Isokinetic Exercise on Steroid Hormone (I)

20. Growth Hormone (GH) • Secreted by the pituitary gland; GH is one of the most potent anabolic hormones • Enhances cellular amino acid uptake and protein synthesis in skeletal muscle, resulting in hypertrophy of both Type I and Type II muscle fibers

21. GH stimulates the release of IGF-1, another anabolic hormone • It has been thought that exercise induced muscular hypertrophy was quite different from that achieved through GH injections; however the two techniques used together may have an additive effect

22. Post Exercise Serum GH Responses

23. Insuline Like-Growth Factors (IGF; Somatomedins) • Temporal increases after resistance exercise • These responses appear to be related to regulatory factors of IGF release and transport • Also related to protein binding, receptor availability, and serum GH

24. Cortisol • Contribute to catabolism through its action in carbohydrate metabolism • Cortisol : • Converts amino acids to carbohydrates • Increases levels of proteolytic enzymes (enzymes that break down protein) • Inhibits protein synthesis • Cortisol may have a greater affect on Type II fibers due to higher protein content

26. Cortisol may be more involved in the control of degradation in Type I fibers • Cortisol increases with resistance exercise, especially when rest periods are short and total volume is high and large muscle groups are used (note similarity to aerobic endurance training). • Cortisol’s role in overtraining, detraining or injury may be critical when muscle tissue atrophy and decreases in force production are observed

27. Effects of Isokinetic Exercise on Steroid Hormone (II)

28. Sympoadrenal production, release and Actions

30. Sympoadrenal Responses to Resistance Training • Before the lift E was at .06, while after it had risen to .3, and dropped back to base levels after 15 minutes of rest

31. Similar results were obtained for NE. That is, at rest, levels were at .4, but rose to 1.26 after the set was completed.

32. Hormonal Response to Resistance Training

33. 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 activated by the resistance training are subject to adaptation, including hormonal adaptations to stress

34. To increase serum testosterone • Use large muscle group exercises, or • Use heavy resistance (85-95% of 1 RM), or • Use moderate to high volume of exercise, multiple sets & exercises, or • Use short rest intervals

35. To increase Growth Hormone Levels • Use workouts with higher lactate concentrations; high intensity , heavy resistance (10 RM) with 3 sets of each exercise (high total work); short rest periods ( 1 minute) • Supplement diet with carbohydrates and protein before & after workout

36. To optimize responses of adrenal hormones • High volume, large muscle groups, short rest periods with varied training protocols, rest periods and volume to allow the adrenal glands to engage in recovery process (secrete less cortisol) and to prevent chronic catabolic responses of cortisol. This attempts to avoid overuse or overtraining.

37. Discussion • What is the most important hormone in adolescent and how it can be promoted by exercise training. • What is the function of anabolic steroids in human body and why it becomes a prohibited substance in sport. • How our endocrine systems response to exercise conditioning in sequence.