muscular adaptations Flashcards
type I
oxidative capacity = high
glycolytic capacity = low
mitochondrial density = high
capillary density = high
myoglobin content = high
connection time = 80-110
nerve conduction = slow
fatigue rate = low
motor unit force = low
fibres per motor neurone = 10-180
type IIa
oxidative capacity = medium
glycolytic capacity = medium
mitochondrial density = medium
capillary density = medium
myoglobin content = medium
connection time = 50
nerve conduction = fast
fatigue rate = fast
motor unit force = high
fibres per motor neurone = 300-800
type IIx
oxidative capacity = low
glycolytic capacity = high
mitochondrial density = low
capillary density = low
myoglobin content = low
connection time = 50
nerve conduction = fast
fatigue rate = high
motor unit force = high
fibres per motor neurone = 300-800
motor unit
motor neurone and all of the muscle cells it innervates
all or nothing law
when a motor neurone fires all of fibres that it innervates contract but the number of neurones firing will differ depending on desired force production
sarcomere structure
myofibril has thousands of sarcomeres
joined in series and parallel
function unit of muscles
made of myofilaments
myosin
300 per thick filament
globular head
flexible tail
myosin heavy chain isoforms
speed of contraction determined by ATPase
capillaries
denser = greater surface area for gas exchange
increased density = improved o2 uptake
vascular endothelial growth factor (VEGF)
stimulates angiogenesis
stimulated by low o2
angiogenesis
blood vessel formation
mitochondria
in cytoplasm
site of ATP production
myoglobin
o2 from cell membrane to mitochondria
higher affinity for o2 than Hb
even at low pp allows o2 store
change in mitochondria over training endurance
36% increase in size
more type I
convert some type Iix to IIa and I
promotes fast to slow shift
endurance training and gene expression
stimulus for altered heavy chain gene expression
benefit of angiogenesis
increase surface area for diffusion
improved rate of o2 transfer
order of muscle fibre recruitment
progressive of I then IIa then Iix as. intensity increases
adaptations to endurance training
change in fibre type composition
increased blood supply
increased mitochondria
increased carb stores
increase fat stores
change in fuel use
increase oxidative enzyme activity
myoglobin response
increase in muscle Mb specifically to trained muscle groups up to 80%
mitochondrial biogenesis
simplified signal transduction pathway
specific detail will relate directly to different tissues and situations
PGC-1a
coactivator responsible for increase in mitochondrial proteins
structural proteins for site of ETC
mitochondrial biogenesis process
decrease glycogen / increase ATP
AMPK (activation via protein kinases)
PGC1 increased expression
mitochondrial genes, biogenesis, glycolysis of fatty acids
GLUT 4 expression
significantly elevated immediately after a single exercise bout
remains elevated for several hours after
returns within 24hrs
training induced responses increases GULT 4 transcription
intramuscular triaglycerol IMTAG
10 males
daily unilateral leg extension
lifted weighted boot
bilateral biopsies
intramyocellular lipids
9 untrained healthy men
alternating endurance and interval
3 day standardised diet leading into measurements
increase in response Ito training
oxidative enzyme activity
sig changes in SDH activity and CS in trained athletes
SDH
oxidises succinate to fumarate
CS
catalyses condensation reaction forming citrate
Fat oxidation
increase in mitochondrial proteins
increased activities of Krebs cycle and ETC
Fat oxidation study
8 untrained women before and after endurance training
12 wks, 5 days/week 1hr @75% vo2 max
vo2max increased 20%
RER decreased significantly at same intensity
training intensity and fat
increased aerobic training aerobic power increases (utilise fats at higher intensity)
detraining
happens quickly within 6 months
cardio vascular and respiratory adaptations
increase max rate of ventilation, Q and SV, extraction of o2 from blood through working muscles
