Exercise Physiology Flashcards
What the 2 types of exercise?
- dynamic: rhythmical movement of joints and contraction/relaxation of muscles (swimming/running/cycling)
- static: maintained contraction for a length of time (weight lifting)
What are the requirements of skeletal muscle for energy?
Need energy for contraction, at rest has low metabolic needs but during exercise muscles perform work so requirements increase, energy comes in form of ATP
What are the 3 energy sources for skeletal muscle?
- immediate ATP from creatine phosphate, fastest supply, no oxygen used, provides store of phosphate to maintain contraction, catalysed by creatine kinase
- anaerobic glycolysis when high ATP requirements, less efficient, no oxygen used, ATP from glucose via glycolysis, forms lactate from excess pyruvate
- aerobic, oxidative phosphorylation, sustained ATP supply, uses oxygen
What is VO2?
maximal oxygen uptake consumed during exercise
- during dynamic exercise using large muscle groups during a few minutes under normal conditions at sea level
- reached when oxygen consumption remains at steady state despite increased workload
- reflects aerobic physical fitness of individual and is important determinant of their endurance capacity during prolonged, sub-maximal exercise
What is the Fick equation?
VO2 = Q x (CaO2-CvO2) Q = cardiac output CaO2 = arterial oxygen content CvO2 = venous oxygen content CaO2-CvO2 = arteriovenous oxygen difference
What is the anaerobic threshold?
The lactate threshold - point where lactate begins to accumulate in the bloodstream, metabolic acidosis occurs and exercise endurance reduces
- varies between individuals and spots, untrained have low AT
What are the 2 things the CVS (central vascular system) does in response to exercise?
- rise in CO through increased SV and HR
- redistribution of CO to active muscles
How is HR and SV increased in exercise?
Sympathetic activity increased -> increased HR and vasoconstriction, positive ionotropic response on heart
Parasympathetic activity decreased
Increased venous return due to vasoconstriction -> increased EDV -> increased preload -> increased SV (Starlings)
OVERALL INCREASED CO
How does HR and SV increase CO?
SV increases until fairly moderate exercise intensity reached
Further increase in CO is reached by HR increase
How does the heart adapt to sustained long term increased blood pressure and demand?
Hypertrophy - increase in cardiac myocyte size
How does hypertrophy change a healthy heart compared to a failing heart?
endurance, strength or combination
increased muscle mass, normal cardiac function, reversible
vs
increased muscle mass, reduced cardiac function, irreversible, cell death & fibrosis
How does HR of athletes compare to normal individuals?
athletes have lower HR - bradycardia
How does distribution of CO differ between when resting vs exercising?
Rest - 20-25% distributed to muscles at 1L/min
Maximal exercise - 80-90% of CO goes to muscle at 22L/min
What are the 2 main mechanisms which control redistribution of blood flow?
- systemic regulation: alpha adrenoreceptors constrict gut vessels and cause vasoconstriction of veins, beta 1 adrenoreceptors in heart increase rate and myocardial contraction, beta 2 adrenoreceptors relax muscle - increase ventilation and oxygen uptake and vasodilation
- local control: local regulatory factors from blood vessels (endothelial mechanisms - NO relaxes SM cells causing dilation, tissue factors - adenosine and inorganic phosphates, carbon dioxide, H+, K+ released from contracting muscles)
How does blood pressure change during exercise?
TPR drops
- increased force of contraction and SV = increase in systolic pressure
- diastolic pressure remains stable or decreases
