1	Chapter 6: Endocrine Responses to Resistance Exercise
2	Adaptations to Stress Endocrine system plays a vital role in the adaptation to stress. Hans Selye’s General Adaptation Syndrome – stress followed by a period of adaptation or improvement in the function The adaptation plateaus, but if stimulus continues it may destroy the organism. Removal of the stress allows recovery and improved function.
3	Resistance Training Programs Only natural stimulus that causes an increase in lean tissue mass. There are many differences in the ability of the resistance program to produce increases in muscle and CT size. The type of resistance training dictates the hormonal response.
4	It has been theorized that the endocrine system can be manipulated naturally with resistance training to enhance the development of various target tissues, thereby improving performance.
5	Synthesis, Storage, and Secretion of Hormones Hormones are chemical messengers synthesizes, stored and released into the blood by Endocrine Glands and other specificialized cells. Neurons synthesize, store and secrete neurotransmitters, which may have hormonals functions. Endocrine glands are signalled to secrete hormones by chemical or neural stimulation
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9	Example of Neural stimulation: Adrenal Medulla secretes the hormone epinephrine on neural stimulation from the brain.
10	Example of Hormonal stimulation: Adrenal Cortex synthesizes and secretes the hormone cortisol after stimulation by another hormone Adrenocorticotropic hormone (ACTH) which is released from the pituitary gland.
11	Basic definition of a hormone stimulation of an endocrine gland results in the release of a hormone into the blood which carries the information to a hormone specific receptor on a target tissue (peptide hormones) or directly to the DNA in the nucleus of the cell (steroid hormones).
12	Autocrine Mechanisms Autocrine secretion of a hormone means the cell releases the hormone inside of itself, via external stimulus, but the hormone never leaves the cell. Example: Insulin-like growth factor (IGF) could be released inside the cell on stimulation of mechanical force production or due to growth hormone interactions with muscle.
13	Paracrine Mechanisms secretion of hormones to interact with adjacent cells, without the need of circulation.
14	Binding Proteins carry hormones in the blood They carry both peptide hormones and steroid hormones Most hormones are not active until separated from their binding protein. Some binding proteins have biological actions
15	Multiple functions Many hormones affect multiple tissues Example: testosterone interacts with almost every tissue in the body; muscle, bone, connective tissue, kidney, and liver. Multiple physiological roles; regulating reproduction; maintenance of the internal environment; energy production, utilization, and storage; and growth and development. Hormones interact with other hormones
16	Muscle as the Target for Hormone Interactions Protein in the muscle cell is controlled by many nuclei in the cell. Muscle remodeling involves the disruption and damage of muscle, inflammation, hormonal actions, and the synthesis of new proteins The inflammatory process involves the immune system under endocrine control
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18	Changes due to resistance training Training adaptation is an increase in actin and myosin. Heavy-chain myosin proteins can change in their structure from type IIb to IIa. Non-contractile proteins are changed in order to establish structural integrity.
19	Protein synthesis Stimulation of protein synthesis by heavy resistance exercise starts at the gene level. Type I fibers depend on the reduction of protein degradation Type II fibers depend on an increase in size; hypertrophy
20	Anabolic Hormones Hormones are involved in the synthesis of protein and degradation mechanisms. Anabolic hormones promote tissue building; insulin, insulin-like growth factor, testosterone, and growth hormone Thyroid hormone facilitates the action of these hormones. Anabolic hormones also block the catabolic hormones; cortisol and progesterone which degrade muscle protein to support gluconeogenesis.
21	The Role of Receptors in Mediating Hormonal Changes Hormone tries to influence the DNA Receptors for the hormone not found on the DNA Receptors function with a specific hormone in a lock-and-key fashion. Some cross-reactivity where a receptor is partially activated with a non-specific hormone; allosteric reactions.
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24	Receptor Domains May be external to the cell membrane Internal to the cell membrane Or, partially inside and outside (integrated) Hormones attach to the receptors causing inhibition or facilitation of protein synthesis When no further adaptation can occur receptors can become nonresponsive to the hormone; a Down reaction
25	Other adaptations Receptors have the ability to increase or decrease binding sensitivity The number of receptors can be altered Testosterone, as a result of exercise, affects only the number of receptors sites but not sensitivity
26	Steroid Hormones vs. Polypeptide Hormones Steroid Hormone Interactions From adrenal cortex and gonads are soluble and diffuse passively across sarcolemma May have transport proteins to facilitate steroid influx After diffusing across the sarcolemma, the hormone binds to its receptor to form a hormone-receptor complex (H-RC) The H-RC acts on the DNA and mRNA is produced for the specific protein
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29	Polypeptide Hormone Interactions Are made up of amino acids; growth hormone and insulin Can bind to receptors in the blood or in the cell membrane of the target tissue Polypeptide hormones can have different receptor domains; internal, external, or integrated.
30	Polypeptide signaling pathways Cyclic AMP-dependent signaling pathway Cytokine-activated JAK/STAT signaling pathway a. Involve a family of soluble tyrosine kinases (known as Janus Kinases) which activate transcription factors called STAT (signal transduction activating transcription) Prototypical growth factor, mitogen-activated signaling pathway
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32	"4." 4. Polypeptide hormones are not fat soluble and cannot penetrate the sarcolemma. 5. Must rely on a secondary messenger (STAT) to relay information 6. The secondary messenger directs its actions to specific areas in the cell
33	Heavy Resistance Exercise and Hormonal Increases Increase in anabolic hormone levels consequent to Heavy resistance exercises Neural stimulation from an alpha motoneuron to a muscle causes other signals from brain (electrical, chemical, hormonal) to a number of endocrine glands. Hormones are secreted during and after the exercise bout
34	"4." 4. The patterns of stress and hormonal responses combine to shape the tissues’ adaptive response to a specific training program. 5. Muscle fibers of the activated motor units are stimulated and forces are placed on the sarcolemmas of the fibers by the heavy external loads lifted. 6. The stress alters the sarcolemma’s permeability to nutrients and affets sensitivity and synthesis of receptors in the membrane
35	"7." 7. Local inflammatory related to tissue damage and repair mechanics are activated 8. The specific force produced in the activated fibers stimulates receptor and membrane sensitivities to anabolic factors, including hormones which lead to muscle growth and strength changes 9. Remodeling follows the exercise session. 10. Synthesis of actin and myosin and a reduction of protein degradation 11.Catabolism occurs if stress is too great.
36	Potential growth Only muscle fibers that are activated by resistance training are subject to adaptation Some fibers are at full potential and will not respond Hormonal interactions are related to the adapted size of the fibers, dictated by loads, and exercise angles used in the resistance training program All motor units in a muscle may not be stimulated to the same extent during an exercise; as well as load patterns, progression schemes Volume of work and type of protocol are vital to the response pattern and magnitude of hormonal changes
37	Mechanisms of Hormonal Interactions Depends on several factors: Increased concentration of blood levels of hormones increases probability of interaction with receptors. If physiological function to be affected is near genetic maximum the receptor will not be sensitive; genetic potential limits size of muscle. Adaptations to heavy resistance exercise is anabolic and related to increases in muscle size. Inapporpriate exercise prescriptions can lead to a catabolic effect and ineffective training program
38	Other factors causing increases in strength Not all force production improvements can be explained by hypertrophy Neural factors integrated with the hormonal factors Some hormonal mechanisms may not be operational in both men and women A myriad of adaptation strategies due to many hormonal mechanisms, program design, training level, sex, genetic predisposition, and adaptational potential
39	Hormonal Changes in Peripheral Blood Many different physiological mechanisms contribute in varying degrees to the observed changes in peripheral blood concentrations of hormones Fluid volume shifts – water shifts from blood to the cell after exercise causing an increased concentration, but still increase receptor interaction probabilities Tissue clearance rates – circulation through certain organ systems keeps the hormones away from potential receptors Hormonal degradation
40	"d." d. Venous pooling of blood – can increase concentrations of hormones in venous blood and increase time of exposure to target tissues. e. Interactions with binding proteins in the blood f. Receptor interactions
41	Adaptations of the Endocrine System The endocrine system itself can undergo a training adaptation. Amount of synthesis and storage of hormones Transport of hormones via binding proteins Time need for the clearance of hormones Amount of hormonal degradatoin that takes place over a given period of time
42	The Primary Anabolic Hormones Testosterone is the primary hormone that interacts with skeletal muscle Dihydrotestosterone is the primary adrogen that interacts with sex-linked tissues Different process in the biosynthesis of testosterone, figure 6.8
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44	"4." 4. Testosterone has both direct and indirect effects on muscle tissue 5. Can promote GH responses in the pituitary, which can influence protein synthesis 6. Also influences the nervous system by increasing the amount of neurotransmitters 7. Can interact with the muscle itself 8. Testosterone is transported from testes in men, ovaries and adrenal glands in women via a transport protein, which goes to membrane or cytoplasm, then migrates to the nucleus, resulting in protein synthesis
45	"9." 9. Increases in blood concentrations of testosterone have been observed in men during and following high-intensity aerobic endurance and resistance exercise; balance catabolism 10. Small testosterone increases in women after resistance exercise 11. Exercise variables that influence Testosterone production Large-muscle group exercise Heavy resistance Moderate to high volume of exercise Short rest periods 2 years or more of resistance training
46	Free Testosterone and Sex hormone-binding Globulin Free testosterone remains unaltered or lower after resistance exercise Younger men have more free testosterone and total testosterone than older men. The bound testosterone may increase the rate of hormone delivery to a target tissue.
47	Testosterone Responses in Women Concentration about 1/15^th to 1/20^th that of men. No acute increase in testosterone after resistance training (figure 6.9)
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49	Training Adaptations of Testosterone Training time and experience influence the resting and exercise-induced concentrations Resistance training with multiple sets, 5-10 RM, adequate muscle mass used. Elite weight lifters showed a concomittant increase in LH and FSH, higher brain regulators of Testosterone May have a role in the NS by augmenting neural adaptations
50	Growth Hormone Anterior Pituitary gland secretes GH Enhances cellular amino acid uptake and protein synthesis in muscle resulting in hypertrophy of Type I and II fibers Direct effect or through IGF-I from liver. Many different target tissues
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52	Main Physiological roles of GH Decreases glycogen utilization Decreases glycogen synthesis Increases Amino Acid transport across cell membranes Increases protein synthesis Increases fat utilization Increases lipolysis Increases availability of glucose and amino acids Increases collagen synthesis
53	"9." 9. Stimulates cartilage growth 10. Increases retention of N, Na, K, and P 11. Increases renal plasma flow and filtration 12. Promotes compensatory renal hypertrophy 13. Enhanced immune cell function Exercise increases secretion of GH
54	The Efficacy of Pharmalogical Growth Hormone 1. GH treatment alone is not effective in causing strength increases and that involvement of the total motor unit is necessary, even though there may be hypertrophy.
55	Growth Hormone Responses to Stress GH increases in response to breath holding, hyperventilation, and hypoxia Not all resistance exercise regimen increase GH; 28% of 7RM for high number of reps, results no change in GH An intensity threshold exists with Longer rest periods >3minutes, may be due to glycolytic metabolism
56	"4." 4. GH increases are sensitive to volume of exercise, amount of rest between sets (less rest more GH), and resistance used (10 RM; with 1 minute rest)
57	Growth Hormone Responses in Women Higher blood levels of GH than men throughout the menstrual cycle With Heavy resistance training (5RM) and long rest periods (>3 min) women showed no increase in GH, however 10 RM and short rest periods (1 min) showed significant increases in serum GH More research needed to confirm the exercise protocol periodization over the course of the menstrual cycle.
58	Insulin-like Growth Factors Liver secretes IGFs after GH stimulates liver-cell DNA, which takes about 8-29 hours. 6 binding proteins regulate the amount of IGF in plasma, and serve as a reservoir for IGFs. IGF can make some cells synthesize the binding protein IGF has a profound effect on synthesizing protein, and interacts with other hormones in response to resistance training and can contribute to muscle hypertrophy and increases in strength
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60	"5." 5. Acute increases in IGF may be due to disruption of the muscle and fat cells from exercise 6. The amount of increase depends on starting concentration; an increase in IGF if basal concentrations are low; no increase if they are high.
61	The Adrenal Hormones Cortisol A glucocorticoid is a primary signal for CHO metabolism and glycogen stores in muscle. When glycogen stores are low in the muscle it stimulates catabolic reactions of protein to provide amino acids for conversion to glucose It increases the level of proteolytic enzymes (breakdown proteins) Inhibits protein synthesis (glucose sparing) More effect on type II fibers
62	"6." 6. Joint immobilization, disease, injury, starvation, etc., causes cortisol to initiate protein degradation. 7. Testosterone and Insulin block the catabolic effects of cortisol 8. Acute increases in serum cortisol following exercise indicate an inflammatory response to tissue remodeling.
63	Resistance Exercise Responses of Cortisol Increases with resistance training, more when rest periods are short and total volume is high. After a period of training testosterone disinhibits cortisol even though the concentration increases Increases in cortisol may indicate that there is a large remodeling process in muscle tissue The testosterone/cortisol ratio also has been used to determine the anabolic-catabolic status of the body, but with limited success.
64	Catecholamines Primarily epinephrine, but also norepinephrine and dopamine, secreted by the adrenal medulla. Important for strength and power expression Act as NS motor stimulators, peripheral vascular dilators, and enhanced enzyme systems in muscles Act to stimulate other anabolic reactions
65	Physiological functions of Epinephrine and Norepinephrine Increase force production via central mechanisms and increased metabolic enzyme activity Increase muscle contraction rate Increase BP Increase energy available Increase Blood flow Augment secretion rates of other hormones such as testosterone.
66	"7." 7. Epinephrine is involved in metabolic control, force production, and the response mechanisms of other hormones, such as testosterone, GH, and IGFs. 8. Stimulation of the catecholamines is one of the first endocrine mechanisms to occur in response to resistance exercise.
67	Manipulating the Endocrine System Naturally with Resistance Training 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.
68	"To Increase Serum Testosterone Concentrations" To Increase Serum Testosterone Concentrations Use large muscle group exercises (e.g., deadlift, power cleans, squats), or Use heavy resistance (85% to 95% of 1RM), or Use moderate to high volume of exercise, achieved with multiple sets or multiple exercises, or Use short rest intervals (60-90s)
69	"To increase Growth Hormone Levels" To increase Growth Hormone Levels Use workouts with high lactate concentrations and associated acid-base disruptions; that is, use high intensity (10RM, or heavy resistance) with three sets of each exercise (high total work) and short (1 minute) rest periods, or Supplement diet with CHO and protein before and after workouts
70	"To Optimize Responses" To Optimize Responses of Adrenal Hormones Use high volume, large muscle groups, and short rest periods, but vary the training 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 of cortisol. This way the stress of the exercise will not result in overuse or overtraining