Exercise Physiology Flashcards
VO2 max of horses
maximum O2 consumption
160ml/kg/min
Athletic capacity of horse
VO2 max = 160ml/kg/min high CO and SV high hematocrit lungs 2x size of cattle large heart mass
Muscle adaptations of the horse
muscle mass is 50% horse BW
high concentration fo intramuscular glycogen - larger number of mitochondria (greater aerobic fitness)
Energy pathways in the horse
1) phosphocreatine kinase - anaerobic, very large amounts of ATP produced very rapidly, only during initial seconds of exercise
2) anaerobic glycolysis - anaerobic, uses glucose, small amount of ATP but rapid production
3) aerobic respiration - aerobic, uses fat if lower intensity or glycogen if higher intensity, slower but produces a LOT of ATP and virtually non-exhaustable
Low intensity exercise
At 20-30% glycogen depletion, animal uses fat as a substrate to conserve glycogen in case they must rapidly produce ATP (ex. they need to run away)
Muscle fibers
3 pure forms, 2 hybrids
differentiated by myosin heavy chain isomers
Type I muscle fibers
slow hydrolysis of ATP
slow twitch, associated with stance or repetitive movements
high number of capillaries, high oxidative capacity, fatigue slowly
forelimbs
Type II fibers
fast twitch fibers, 3 types
generate force rapidly
hind limbs
Type IIA fibers
IIA: fast oxidative glycolytic fibers (FOG)
- high power for long periods
- large # capillaries and mitochondria
Type IIX fibers
IIX: fast glycolytic fibers (FG)
- high power output for short duration, faster production (3x faster than IIA)
- large cross sectional area, low capillaries
IIAX
fall between type IIA and IIX fibers
MM fiber recruitment
Type I –> Type IIA –> Type IIAX –> Type IIX
Type IIX reseved for max intensity exercise
depends on nature, intensity and duration of exercise, muscle fibre type composition, available O2, substrate compostition
