stre&cond - chapter 4: endocrine responses

hormones

integral part of protein synthesis and degradation related to resistance training muscle adaptations

• MUSCLE is the target

• includes anabolic (promote building/repair) and catabolic (degrading cell proteins)

1) steroid

2) peptide

3) amine

steroid

hormones synthesized from cholesterol in adrenal cortex/gonads

• passive diffusion: through sacrolemma of muscle fiber bc of lipophilic nature

  • binds with H-RC in the cell → moves hormone to nucleus → interacts with DNA

steroid hormones

androgens: testosterone — muscle building and strength

estrogens: reproduction, bone density, CV protection, cognitive function

glucocorticoids: cortisone, cortisol — stress, tissue breakdown for gluconeogenesis

prostaglandins: bodily functions like BP, BF, inflammation, etc

anabolic: muscle building, regulating energy, reproduction

peptide

hormones made of short chain of amino acids (long chains of AA = polypeptide)

• NOT fat-soluble and cannot pass lipid layer in cell membrane

• binds with surface receptors → use secondary messengers = signal transduction

peptide hormones

insulin and glucagon: blood sugar and energy regulation

growth hormone (GH) and insulin-like growth factor-1 (IGF-1): body growth, tissue repair, protein synthesis, metabolic function

leptin: appetite

amine

hormones derived from single amino acids

• synthesized from tyrosine, phenylalanine, tryptophan

• usually bind to surface receptor → second messenger

• some can act as neurotransmitter (released across synapses) in ANS

amine hormones

catecholamines: epinephrine, norepinephrine, dopamine — influence how the body handles stress (fight or flight), mood, motivation, etc.

hormone transport

either go through classic pathway after gland stimulation OR bypass bloodstream

• classic: gland stimulated → release hormone to bloodstream → transported to target tissues (ex: pancreas releases insulin)

• bypass bloodstream:

  • intracrine — bind to internal receptors within cell (ex: IGF-1 produced in and affects muscle cell directly)

  • autocrine — cell secretes hormone and binds to surface receptors of the same cell

  • paracrine — cell releases chemicals that affect adjacent cells via simple diffusion

• half life

• transport binding proteins

half life

time it takes for half of hormone to be degraded, different depending on the hormone

• transport (binding) proteins: bind to hormones → protects hormones → stays in blood longer → longer half-life

  • if it was unbound, it’d be free in blood to be broken down/taken up/excreted

• ex: sex hormone-binding globulin to testosterone and estrogen

feedback loops

how the body controls hormone levels

• negative — used mostly: production of hormone reaches concentration that meets demands and further production is stopped (too high, then lower — too low, then raise)

  • ex: stress → hypothalamus → CRH → pituitary gland → ACTH → adrenal cortex → cortisol

• positive: increasing concentration of a hormone (ex: oxytocin and childbirth)

hormone concentration

hormone’s concentrations change because of:

• degradation: broken down/removed from blood

  • binding proteins protect hormones from breakdown

• secretion: how much the gland releases and can be released at diff times/patterns

  • circadian: depending on time of day (ex: testosterone highest in morning)

• fluid shifts: less fluid = higher concentration, more fluid = less concentration

  • amount of hormone doesn’t change (ex: dehydration and less blood plasma = hormone appears more concentrated)

• uptake: interact with receptors to cause an affect

  • acutely: normal increase in hormone → pathway working properly and up-regulating for intended purpose → cell is responsive

  • chronically: constant high levels of hormone → receptor down-regulation or resistance → cells less responsive

acute homeostatic response

sharp increase or decrease in hormone concentrations that return to normal levels after exercise

• what happens during one workout?

• ex: testosterone levels increase following exercise and slowly return to resting levels

chronic homeostatic adaptations

gradual increase or decrease in hormone concentrations over time after weeks/months of consistent training

• hormonal changes at rest

• changes in acute response: how strongly hormones respond during exercise

  • can become more effective at producing/releasing certain hormones when needed

  • what changes after many workouts?

• ex: catecholamine response to exercise increases following months of endurance training

training-mediated

resistance training affects muscles, connective tissue, and other physiological systems

• hormone secreted before, during, and after resistance exercise due to physiological stress

• muscle remodeling: multi system process: skeletal, nervous, endocrine, immune, circulatory

  • allows for adaptation – ex: hypertrophy and repair

• skeletal muscle: transforms mechanical stress → chemical signals = grow bigger and stronger

• ⭐ specific force produced in activated fiber → stimulates receptor and membrane sensitivities TO anabolic factors → muscle growth and strength changes

general adaptation syndrome

hormone response to a noxious stimuli (potentially damaging to body tissue) such as exercise

• governs the hormonal response to resistance training

• alarm phase: endocrine and immune elevated to respond to stimulus

  • stress resistance initially decreases

  • mobilize resources, increased SNS, stress hormone (epi and cortisol) release

• adaptation phase: hormonal response returns to resting levels and starts to recover

  • coping with the stressor

  • appropriate recovery = body better handles stressor

  • stress resistance higher than before

• exhaustion phase: stressor isn’t resolved = body reserves/resources are depleted

  • hard workout with no recovery = overtraining syndrome

  • hormone regulation disrupted

anabolic hormones

hormones that buildup/repair tissues and store energy

• testosterone

• growth hormone

• insulin-like growth factors

catabolic hormones

hormones that breakdown molecules to release energy

• cortisol

• catecholamines

testosterone

anabolic hormone that supports muscle growth, repair, and protein synthesis

• most is bound to proteins (SHBG)

• free: small portion of total not bound and more readily available to interact

resistance training:

• men: total and free increases immediately → return to resting levels

• women: acute change and increase in free

• greatest acute response: high int, large muscle exercises, short rest

• chronic adaptation (2+ years): number of receptors = greater interaction with muscle cells

growth hormone

anabolic hormone released from pulsatile manner in pituitary gland that supports body growth, tissue repair, protein synthesis, metabolic function

• females: resting values higher, variances depend on menstrual cycle, and blunted response with oral contraceptives

• no apparent change in resting values with consistent exercise (acute response)

• stimulates IGF-1

resistance training:

• response sensitive to total work performed — intensity, sets, reps = volume load

  • higher work = higher acute response

• high intensity

• sensitive to acidity

• short rest periods

IGFs

anabolic hormone produced by liver in response to GH stimulation

• structurally related to insulin

• muscle mechano growth factor: important for acute increases in protein synthesis and satellite cell activity due to RT

resistance training: influence is not fully understood

• highly trained men and women see affects of resting and acute response

• follow guidelines for acutely increasing T and GH

cortisol

catabolic hormone stimulated by ACTH and produced in adrenal cortex

• acute increases: reflect metabolic needs

  • gluconeogenesis: maintain blood glucose

  • inhibit protein synthesis

• chronic increases: suppress immune function and cause catabolism

resistance training:

• higher volume, large muscle group exercise = greater increase in concentration

  • drive sharp increase but acute stressors can benefit

• men higher levels = need longer recovery

• women rapidly adjust receptor sensitivity post-exericse

catecholamines

catabolic hormone produced in medulla that stimulates the nervous system

• epinephrine, norepinephrine, dopamine

• fight or flight, vasodilation, enzyme activity, calcium release

• help augment secretion of other hormones (ex: T)

• higher concentration = greater force production

resistance training:

• heavy RT = acutely release greater amt during max exercise

• decrease concentrations during familiar tasks (balancing)

• high stress continuously = adrenal exhaustion

exercise protocol

to maximize endogenous production of hormones (using the endocrine system)

• high INT, near maximal — 80-95% 1 RM

• big and heavy exercises: deadlift, squats, bench press, etc — systemic stress response

• short rest periods: rely on anaerobic systems and H+ accumulates

• 1-10 — 5 mod-high