Hormones And Exercise PDF

Hormonal Regulation of Metabolism in Exercise  Responses to Exercise What are some acute responses to exercise? What are some chronic adaptations to exercise training? What are some chronic adaptations to the acute responses to exercise??? WHY AM I ASKING THESE QUESTIONS TO BEGIN THE...

Hormonal Regulation of Metabolism in Exercise  Responses to Exercise What are some acute responses to exercise? What are some chronic adaptations to exercise training? What are some chronic adaptations to the acute responses to exercise??? WHY AM I ASKING THESE QUESTIONS TO BEGIN THE HORMONES CHAPTER???? 2 Acute Hormonal Responses Fig. 4.4. Kenney et al. 2019. Physiology of 3 Sport & Exercise. Hum.Kin.  Hormonal Regulation of Metabolism During Exercise These major endocrine glands are responsible for metabolic regulation: Anterior pituitary gland Thyroid gland Adrenal gland Pancreas (next lecture) Hormones released by these glands affect metabolic rate and metabolism of carbohydrate and fat during exercise. Pituitary Hormones And their downstream effects  Anterior Pituitary Gland Pituitary gland is attached to the inferior hypothalamus.  Controlled by hypothalamus Its three lobes are the anterior, intermediate, and posterior. Pituitary gland secretes hormones in response to hypothalamic hormone factors:  Includes both releasing factors and inhibiting factors.  Exercise causes stress, which is sensed by the hypothalamus. It then tells the pituitary to release hormones to restore homeostasis.  Anterior Pituitary Hormones Anterior pituitary secretes six specialized polypeptide hormones Each of the primary pituitary hormones has its own hypothalamic releasing hormone called a releasing factor  Neural input to the hypothalamus from anxiety, stress, and physical activity controls output of these releasing factors Fig. 20.5. McArdle et al. 2010. Exercise Physiology… LWW  Growth Hormone Growth hormone (GH) is a peptide hormone that promotes cell division and cellular proliferation throughout the body Resting levels higher in women Stimulated by GH-releasing hormone from hypothalamus GH is a potent anabolic hormone Promotes muscle growth (hypertrophy) Increases amino acid transport through the plasma membrane Activates cellular ribosomes that increase protein synthesis Stimulates release of insulin-like growth factors (IGFs) from liver Stimulates fat metabolism and slows carb (glycogen) breakdown  Growth Hormone Gluconeogenesis Actions IGFs Fig. 20.6. McArdle et al. 2010. Exercise Physiology… LWW  Growth Hormone and Tissue Synthesis Acute increase in response to exercise  Greater increase, with higher intensity / stress  Benefits muscle, bone, and connective tissue growth and remodeling  Optimizes the fuel mixture during physical activity  The net metabolic effect preserves plasma glucose concentration for central nervous system and muscle functions Effects of exogenous HGH on muscle hypertrophy are unclear  Some evidence for benefits for connective tissue repair (though still illegal in sports)  Possible benefit for elderly, but controversial side effects  http://www.youtube.com/watch?v=Tel4kYn_rIU  Growth Hormone Regulation Trained and sedentary individuals show similar increases in GH concentration with exercise to exhaustion but the sedentary person maintains higher GH levels for several hours into recovery  Nochronic effect of training on resting levels. Powers et al. 2009.  High GH levels Exercise in adulthood Physiology… McGraw Hill lead to acromegaly (gigantism)  Insulin-Like Growth Factors IGFs mediate many of GH’s effects  Believed to be one of the primary stimulators of hypertrophy In response to GH stimulation, liver cells synthesize the peptide hormones IGF-I and IGF-II IGFs travel in the blood attached to one of five types of binding proteins for release as free hormones to interact with specific receptors IGFs have potent anabolic effects:  Increase amino acid transport  Stimulate DNA transcription  Stimulate ribosomal translation “Deer antler spray” controversy  Thyroid Gland Anterior pituitary releases thyrotropin. Isalso called thyroid-stimulating hormone (TSH). Exercise increases TSH release. TSH travels to thyroid, stimulates T3 and T4. T3 and T4 are amine hormones that bind to intracellular receptors that lead to increases in  metabolic rates of all tissues  protein synthesis  number and size of mitochondria  glucose uptake by cells  glycolysis and gluconeogenesis rates  FFA mobilization Adrenal Hormones  Adrenal Hormones The adrenal glands have two distinct parts:  Medulla: Acts to prolong and augment sympathetic effects by secreting epinephrine (80%) and norepinephrine Epi is also known as “adrenaline”, while NorEpi is noradrenaline. These are also amine hormones that are collectively know as catecholamines  Cortex:Secretes steroid adrenocortical hormones that fit functionally into one of three groups: Mineralocorticoids, glucocorticoids, and gonadocorticoids (androgens) Fig. 20.9. McArdle et al. 2010. Exercise Physiology… LWW  Catecholamines Essential part of Cannon’s “Fight or Flight” response  Amine hormones that act via 2nd messengers (e.g. cAMP system)  Epi and NE also neurotransmitters that can be released from sympathetic nerve endings Norepinephrine (NE) is an epinephrine (Epi) precursor Metabolic effects:  Both stimulate glycogenolysis and lipolysis  Also stimulate glucagon secretion and inhibit insulin  Maintains blood glucose Glycogen- olysis Fig. 20.10. McArdle et al. 2010. Exercise Physiology… LWW  Adrenal Medulla Releases catecholamines (fight or flight). Epinephrine 80%, norepinephrine 20% – Exercise  sympathetic nervous system  epinephrine and norepinephrine Catecholamine release increases. Heart rate, contractile force, blood pressure Glycogenolysis & lipolysis Blood flow to skeletal muscle  Catecholamines and Exercise  Increase abruptly with the onset of exercise  Levels are highly correlated with exercise intensity  Levels gradually fall during prolonged, moderate intensity exercise  Exercise training blunts catecholamine response Fig. 5.14. Powers et al. 2009. Exercise Physiology… McGraw Hill Fig. 20.11. McArdle et al. 2010. Exercise Physiology… LWW Adrenergic Receptors How do catecholamines facilitate so many Receptor type determine cells’ response to acute responses to hormone exercise? Also called adrenergic receptors Activates 2nd messenger system, either cAMP or [Ca] Two classes of receptors: α- receptors  Vasoconstriction  ↑ blood clotting  Opposes β receptor responses β- receptors increase  Vasodilation  Bronchodilation  Heart rate & contractility  Glycolysis, Glycogenolysis (muscle)  Glycogenolysis (liver)  Lipolysis (adipose) Adrenergic Receptors Many common medications utilize these adrenergic receptors What benefit would a Beta agonist provide? What benefit may a Beta blocker provide? What benefit may an Epi-pen provide? Adrenergic Receptors How does the body “know” where to redirect  These receptors are also responsible for some blood flow during of the blood flow changes that we know take exercise? place during exercise. Fig. 8.8. Kenney et al. 2020. Physiology of Sport… Hum.Kin.  Adrenal Cortex Releases corticosteroids. Glucocorticoids Alsomineralocorticoids, gonadocorticoids Major glucocorticoid is cortisol. Why would a “steroid” shot Stimulates gluconeogenesis. be beneficial? Known as a “stress” hormone Acts as an anti-inflammatory, depresses anti- immune reactions. Increases FFA mobilization, protein catabolism. Cortisol typically referred to as a “catabolic” hormone due to its effects on protein. Main function of cortisol is to maintain blood glucose Fig. 20.9. McArdle et al. 2010. Exercise Physiology… LWW Gonadocorticoids The reproductive organs provide the major source of the so-called sex steroids, but the adrenal cortex produces gonadocorticoids with similar actions The adrenal cortex produces dehydroepiandrosterone (DHEA), which exerts effects similar to the dominant male hormone testosterone The adrenal cortex also produces small amounts of the “female” hormones estrogen and progesterone Gonadal Hormones  Gonadal Hormones No “male” or “female” hormones exist but rather general differences in hormone concentrations between the sexes Testosterone is the most important androgen secreted  Initiates sperm production and stimulates development of male secondary sex characteristics The ovaries provide the primary source of estrogens (estradiol, progesterone)  Estrogens regulate ovulation, menstruation, and physiologic adjustments during pregnancy  Progesterone contributes regulatory input to the female reproductive cycle, uterine smooth muscle action, and lactation  Testosterone Testosterone  The primary androgen hormone that interacts with skeletal muscle tissue  Large muscle group exercises, higher volume & shorter rest result in acute increased serum total testosterone concentrations in men.  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. Serum Testosterone Responses to Exercise  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 Fig. 3.9. Baechle et al. 2009. Essentials of Strength… Human Kinetics Fig. 20.14. McArdle et al. 2010. Exercise Physiology… LWW  Testosterone Anabolic Steroids  Adverse Effects The medical problems related to anabolic steroids may be somewhat overstated. Many of the side effects linked to abuse are reversible upon cessation. Side effects differ between anabolic steroid use under medical supervision and consuming many drugs at high doses. Most severe cases seen in body-builders  Majority of anabolic steroid ‘research’ is anecdotal, due to a lack of well- designed studies. Fig. 8.2. Baechle et al. 2009. Essentials of Strength… Human Kinetics Prohormones Testosterone Precursors (Prohormones)  Taking hormones that are precursors to testosterone  Very little evidence of ergogenic benefits  May present higher risk for adverse side effects similar to those associated with anabolic steroid use.  i.e. androstenedione, DHEA Hormonal Control of Lipolysis  Regulation of Fat Metabolism During Exercise FFA mobilization and fat metabolism are critical to endurance exercise  Glycogen depleted, fat energy substrates needed  In response, fat breakdown (lipolysis) accelerated Triglycerides (aka triacylglycerol)  glycerol + 3 FFAs  Fat stored as triglycerides in adipose tissue  Broken down into free fatty acids, transported to muscle  Rate of triglyceride breakdown into FFAs: possible determinant of rate of cellular fat metabolism Lipolysis is stimulated by: (decreased) insulin cortisol epinephrine norepinephrine GH TAG (triacylglycerol) 1 Glycerol + 3 FFA  Regulation of Fat Metabolism During Exercise Stimulate lipolysis via the Cyclic AMP Pathway & Hormone-Sensitive Lipase cAMP pathway: GH, Epi or NE epinephrine norepinephrine GH They stimulate lipolysis via activation of hormone-sensitive lipase (HSL) enzyme via the cAMP pathway. HSL TAG (triacylglycerol) 1 Glycerol + 3 FFA  Figure & Notes References Kenney, Wilmore, Costill. Physiology of Sport and Exercise (7th ed). Human Kinetics, 2018. McCardle, Katch, Katch. Exercise Physiology: Nutrition, Energy, and Human Performance, 8th Edition. Wolters Kluwer Health, 2014. Baechle & Earle. Essentials of Strength & Conditioning, 4th Edition. Human Kinetics, 2016. 34