B6.084 Exercise and Muscle Function Flashcards
what is VO2
rate of oxygen consumption
how does rate of oxygen consumption change from rest to max
can increase 12x
VO2 equation
VO2 = Q * (a-vO2 diff)
how does rate of cardiac output change from rest to max
can increase 4x
how does rate of tissue oxygen extraction change from rest to max
can increase 3x
measured by arteriovenous oxygen difference
role of skeletal muscle in oxygen consumption
O2 delivery -muscle blood flow capacity O2 exchange -muscle capillarity ATP production -mitochondrial content -mitochondrial function
typical resting VO2
3.5
what diseases are increased in individuals with low aerobic capacity
CVD stroke metabolic syndrome breast cancer colon cancer Alzheimer's dementia PCOS fatty liver
max VO2 in aerobically trained individuals vs. sedentary individuals
higher in aerobically trained individuals
aerobic trained age 80 = sedentary age 50
VO2 max frailty threshold
18
can no longer perform ADLs below this level
how do drugs impact the relationship between exercise and VO2 max
common drugs like statins and metformin can block exercise adaptations (impinge on mitochondrial function)
what increases a-vO2 diff
NOT due to elevated arterial O2 content
due to enhanced extraction
training adaptations that increase maximal exercise a-vO2 diff
increased muscle blood flow increased capillaries (primary cause) increased mitochondria (secondary cause)
cellular signals in response to exercise that initiate changes in gene expression
increased AMP/ATP ratio
intracellular Ca2+
coordinated response to changes in gene expression with exercise
increased angiogenic growth factors mitochondrial genes contractile protein genes LEAD TO increased O2 delivery and consumption
where are mitochondrial most adaptive
subsarcolemmal mitochondrial respond to exercise/inactivity
how do mitochondria change in response to endurance exercise
increased density
higher cristae density (better functioning, more ETC activity)
enzymes that increase with exercise training
fat oxidation enzymes
- acyl coA synthetase
- CPT-1
- AMPK
- B oxidation
- TCA enzymes
result of increasing fat oxidation with exercise
use more FFAs for energy over carbs bc more fat is available in the body
“crossover concept”
with increasing aerobic power/work you increase carb utilization and decrease fat utilization
rate limiting steps of glucose uptake by skeletal muscle
supply: -perfusion -blood glucose concentration transport: -surface membrane GLUT abundance -glucose gradient -GLUT activity metabolism: -hexokinase activity -substrate flux
function of hexokinase
phosphorylates glucose to keep it in the cell
what allows for glucose transport into skeletal muscle
insulin receptor activity activates GLUT4 to translocate to membrane
contraction (exercise) activates GLUT4 to translocate to membrane
best recipe for glucose uptake
insulin + exercise
how does exercise aid in improving insulin sensitivity?
- increased protein content of GLUT4
- increased protein content and activity of glycogen synthase
- increased glycogen storage
- muscle fiber conversion to more oxidative/ less glycolytic
- increase arteriole dilation with insulin stimulation
- changes in the expression of activation of insulin signaling proteins are less consistently found
3 types of muscle fibers
type 1: slow twitch red, endurance (oxidative)
type 2a: fast twitch red, intermediate (oxidative and glycolytic)
type 2b: fast twitch white, power/fatigability (glycolytic)
why are slow twitch muscles red
very oxidative, contain a lot of iron
fast twitch white motor units
larger with more fibers
used in max force activities
less mitochondria
less capillarity
slow twitch red motor units
smaller with fewer fibers
used in ADLs
finite movements
more capillarity
effects of exercise on blood vessels
induces:
angiogenesis (cap density)
arteriogenesis (more branches)
artery enlargement (increased endothelium dependent dilation)
flow mediated dilation
lower value is associated with increased mortality
measures dilatation as blood flow rushes in after constriction with cuff is removed
how do muscles grow?
increased cross sectional area of myofibers
what is responsible for early gains in strength
neural adaptations
different motor unit/fiber type activations
central neural adaptations
motor cortex activity increases when the level of force developed increases and when new exercises or movement are being learned
adaptations of motor units
maximal strength and power result from an: -increase in recruitment -rate of firing -synchronization of firing or a combo of the above
adaptations of NMJs
possible changes with anaerobic training include:
- increased area of the NMJ
- increased end plate perimeter length and area
- greater dispersion of ACh receptors within the end plate region
order of recruitment of fibers with increased power exerted
slow twitch red
fast twitch red
fast twitch white
muscle hypertrophy
increased size and number of actin and myosin fibers
NO CHANGE IN NUMBER OF MUSCLE FIBERS
