Endocrine System and
Exercise
Glucose uptake increases during
exercise
 Release from kidneys, gut, and liver
 Make new from 3-carbon molecules (LA,
pyr., glycerol, and alanine, LA most
important)
 Deliver alternative substrates to the active
tissue (FAs, triglycerides, lactate, aa
leucine)
Increased glucose causes insulin
levels to rise
Insulin Antagonists
 Insulin stimulates glycogen storage, epi and
glucagon stimulate glycogen breakdown
 Insulin stimulates protein synthesis
 Leptin is an anabolic hormone that promotes
use of energy
 Cortisol promotes catabolism and release of
aa’s from muscle into blood
Energy Storage
Insulin
FFA
Carbohydrates
Leptin
Energy Dissipation
Feed-forward control
 When exercising, catacholamine-mediated
stimulation of hepatic glucose production
(why?)
Hormones
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Chemical messengers
Generalized in action an circulate widely
Some specific, localized effect (ACH)
Norepi is both local and general
Two types of hormones:
 Steroid: produced by the adrenal cortex and
gonads, made from cholesterol
 Polypeptides: aka small proteins, derived
from aa’s in other endocrine glands
Action:
 Usually bind on specific sites on target
tissue, binding can:
 Affect permeability
 Activate an enzyme or enzyme system
 Activate genetic apparatus to manufacture
intracellular proteins or other substrates
 Increase secretatory activity
cyclic AMP (cAMP)
 Many hormones, when bind to a tissue form
cAMP
 cAMP activates many systems
 Second messenger
Low intensity exercise
 Little effect on hormone levels
 >50% VO2max see elevation in
catecholamines
 Why?
 With training, lower
 Moderate exercise, the same or enhanced
response
 Why?
Insulin and glucagon: immediate
control of blood glucose
 Insulin stimulates uptake, glycogen and fat
synthesis
 Glucagon, secreted when blood levels are
low, acting to raise those levels
 Two effects:
– Enhance glycogenolysis
– Increase glycogenolysis (indirectly stimulating
beta oxidation)
Liver’s role in stabilizing blood
glucose levels
 HGP is considered representative of
glucose production
 Critical for overall homeostasis
 Levels are high, store
 Levels are low, release