Endocrine System and Resistance Training CHAPTER 6 3

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Endocrine System and Resistance Training

• CHAPTER 6

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Objectives

• Understand hormones and target tissue
• Explain anabolic and catabolic hormones
• Describe hormone responses to strength training
• Design training programs to stimulate hormone
  secretion

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Endocrine Glands

• Secrete substances (hormones) into blood or body
  fluid
• Promotes homeostasis
• Based on Selyes General Adaptation Syndrome
• Tissue adaptations are related to endocrine
  responses to exercise

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• Hormones- chemical messengers synthesized and
  released by endocrine glands
• Nervous system- fast and short acting
• Endocrine system- slow and longer lasting
• Target tissue- the tissue the hormone effects

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• Peptide hormones (protein)- indirectly effects
  cell function by binding to a hormone receptor
• Steroid hormones (fat)- directly effect the DNA
  in the nucleus of a cell
• Hormones function in reproduction growth and
  development energy production, utilization, and
  storage immunity

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Major Endocrine Glands

• Liver
• Adrenal cortex
• Adrenal medulla
• Pancreas
• Ovaries/testes

• Hypothalamus
• Pituitary
• Thyroid
• Parathyroid
• Heart

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Endocrine Function in Muscle

• Muscle tissue is remodeled with exercise
• Muscle is multinucleated with one nucleus
  controlling a nuclear domain
• Increase in actin and myosin
• Conversion of IIx to IIa fibers
• Increase in size
• Type I, decrease in protein degradation
• Type II, increase in protein synthesis

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HormonesAnabolic vs. Catabolic

• Build up
• Protein synthesis
• Hypertrophy
• Occurs more in type II muscle fibers

• Break down
• Protein degradation
• Atrophy
• Occurs more in type I muscle fibers

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Hormonal Mechanisms

• Lock and key mechanism- hormone is the key
• Cross reactivity- a receptor partially interacts
  with another hormone
• Allosteric binding sites- non-hormone substances
  can bind to the cell membrane to enhance or
  reduce the cellular response to the hormone
• Down regulation - a receptor can become less
  sensitive to a hormone

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Lock and Key
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HormoneSteroid VS Peptide

• Lipid- fat soluble
• Forms hormone-receptor complex
• Direct effect on nucleus
• EX testosterone

• Protein- water soluble
• Uses second messengers as signals to nucleus
• EX growth hormone

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Hormonal Response to Heavy Resistance Training

• Hormonal secretions related to
• Amount and type of stress
• Metabolic demands of exercise
• Changes in resting metabolism
• Hormonal response occurs only in tissue exercised

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Mechanisms of Hormone Interaction

• Increased concentration of hormones facilitates
  interaction
• Recovery from anaerobic exercise promotes cell
  growth (anabolism)
• Inappropriate exercise prescriptions can result
  in a net catabolic effect

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Hormonal Changes in Peripheral Blood

• Blood levels may not be an indicator of
  specifically what is happening in the target
  tissue
• Increase- increases probability of
  hormone/receptor interaction
• Decrease- cellular uptake, degradation of
  hormone, decreased secretion of the hormone

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Mechanisms Related to Blood Concentrations of
Hormones

• Fluid volume shifts
• Tissue clearance rates
• Hormonal degradation
• Venous pooling of blood
• Binding with proteins in the blood
• Receptor interaction potential

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Adaptations in the Endocrine System

• Synthesis and storage of hormones
• Transport of hormones via binding hormones
• Time for hormone to clear liver and other tissues
• Rate of hormone degradation

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• Blood to tissue fluid shift during exercise
• How tightly hormone binds to receptor
• Number of receptors in the tissue
• Magnitude of signal sent to cell nucleus
• Degree of interaction with cell nucleus

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1. Testosterone

• Primary male sex hormone, does have an effect in
  females
• Growth
• Protein anabolism
• Male secondary sex characteristics

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Secondary Sex Characteristics
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Testosterone

• Direct effects-
• Interacts directly with muscle tissue
• Indirect effects-
• Promotes the action of GH from the pituitary
• Interacts with the NS to increase production of
  neurotransmitters

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Increasing Serum Testosterone

• Large muscle-mass exercises
• Heavy resistance (80-95 1RM)
• Moderate to high volume
• Short rest intervals
• 2 or more years training experience

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Testosterone in Women

• Secreted from ovary and adrenal gland
• 15-20 times lower concentration in women than in
  men
• Training increases testosterone in women very
  little or not at all

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2. Growth Hormone

• Secreted by anterior pituitary
• Enhances cellular uptake of amino acids and
  protein synthesis in type I and type II muscle
  fibers
• Has both direct and indirect (through IGF-1)
  effects on muscle
• Injections of GH stimulate muscle hypertrophy
  (with decreased ability to produce force)

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Main Effects of GH

• Decreases glucose utilization
• Decreases glycogen synthesis
• Increases protein synthesis
• Increases utilization of fatty acids
• Increases lipolysis
• Increases availability of glucose and amino acids

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• Increases collagen synthesis
• Stimulates cartilage growth
• Increases retention of nitrogen, sodium,
  potassium, phosphorus
• Increases renal plasma flow and filtration
• Promotes renal hypertrophy
• Enhances immune function

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3. Insulin-like Growth Factors (IGF-1)

• Polypeptide hormones secreted from the liver
• Mediate some effects of GH
• Stimulate protein synthesis
• Variable changes with resistance training in
  males
• Little or no change with resistance training in
  females

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4. Cortisol

• Glucocorticoid from the adrenal cortex
• Stress hormone
• Converts amino acids to CHO
• Increases proteolytic enzymes
• Inhibits protein synthesis
• Short term increases related to tissue remodeling
• Long term increases related to overtraining

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5. Catecholemines

• Epinephrine, norepinephrine,
• Increase force production in muscle
• Increase muscle contraction rate
• Increase blood pressure
• Increase blood flow
• Increase secretion rates of other hormones

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Summary Resistance Training and the Endocrine
System

• Remodeling occurs only in the muscle fibers used
  during training, including hormonal adaptations
• Recruiting more muscle fibers increases the
  potential for adaptation

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To Increase Serum Testosterone

• Use large muscle mass exercises
• Use heavy resistance
• Use multiple sets or exercises
• Use short rest intervals (60-90 s)

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To Increase Growth Hormone

• Use protocols that stimulate high lactic acid
  production (high intensity, 10RM, short rest
  periods)
• Use carbohydrate and protein supplements before
  and after the workout

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To Optimize Adrenal Responses

• Use high volume, large muscle mass exercises with
  short rest periods
• Vary the training program to allow the adrenal
  response to promote recovery
• Monitor for overtraining

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Next Class

• Chapter 5 Bioenergetics