38. Exercise physiology Flashcards
What are the two types of exercise and how does muscle usage differ accordingly?
Dynamic exercise - rhythmical movements of joints and contraction and relaxation of muscles e.g. swimming, running and cycling
Static exercise - maintained contraction for a length of time e.g. lifting
What are the sources of energy for skeletal muscle function?
Immediate - creatine phosphate/phosphocreatine (no o2)
Non-oxidative - anaerobic glycolysis
Oxidative - aerobic/oxidative metabolism
Describe the immediate source of energy for skeletal muscles
Creatine phosphate - high concentrations of this in the muscle
This provides a high storage of high-potential phosphate to maintain contraction
Catalysed by creatine kinase
Describe anaerobic glycolysis and the consequences of this
Excess pyruvate is converted to lactate
There is a lactic acid build up
So there is a drop in the pH and the muscle begins to fatigue
What is ‘VO2’?
This is the volume of oxygen that is consumed during oxidative metabolsim
What is ‘VO2 max’?
This is the highest peak oxygen uptake that an individual can obtain during dynamic exercise (whilst using large muscle groups during a few minutes under normal conditions at sea level)
This is reached when the oxygen consumption remains at a steady state despite an increase in workload
What is the significance of VO2 max?
VO2 max reflects the aerobic physical fitness of the individual
Is an important determinant of their endurance capacity during prolonged, sub-maximal exercise
What is the anaerobic threshold?
(aka. the lactate threshold)
This is where further increases in work are not accompanied by oxygen uptake - the blood lactate rises steeply
SO the anaerobic threshold is the point where lactate begins to accumulate in the bloodstream
Varies from person to person
How can the anaerobic threshold be improved?
Untrained individuals have a low AT whilst elite endurance athletes have a high AT
What is the aim of the cardiovascular system during exercise?
Aim is to increase oxygen delivery to the skeletal and cardiac muscle
What are the main responses of the CVS during exercise?
- Rise in cardiac output via an increase in SV and HR
2. Redistribution of larger proportion of CO to the active muscles
How is the heart rate increased by the CVS?
Generally, HR is kept low by the vagus nerve (parasympathetic) so during exercise, there is a reduced activity of parasympathetic and increased activity of sympathetic nerves
Sympathetic nerves also act to cause partial vasoconstriction of blood vessels
Together this results in an increased HR and mobilisation of blood from the great veins
How is the stroke volume increased by the CVS?
Increased venous return
Increased end diastolic volume (and hence increased preload)
According to Starling’s law, this increases the SV
Sympathetic activity has a positive inotropic response on the heart (increased force of contractility)
What is the main component that can increase the cardiac output?
Mainly due to an increased heart rate - the stroke volume reaches maximum levels at a fairly moderate exercise intensity
What is ‘heart remodelling’?
This is a long term response of the heart to increased levels of exercise (physiological cause) pr can be due to a disease (pathological cause)
Heart adapts to sustained increases in BP by increasing muscle mass via hypertrophy (increased cardiac myocyte size)