L19- Physiological adaptations to exercise

define VO_2max

the maximum amount of oxygen delivered to the working tissues and utilised in aerobic metabolism

what is VO₂ a measure of

the rate of aerobic respiration

what is VO_2max a measure of

the maximal rate of aerobic metabolism

How do we quantify the impact of exercise upon respiration

increasing exercise generates an increased O₂ demand which results in an increase in VO₂

what is the utilisation theory

VO_2max is determined by the body’s ability to utilise the available oxygen

what is the presentation theory

VO_2max is the ability of the body’s cardiovascular system to deliver oxygen to active tissues

what did a study by Saltin and Rowell conclude (1980)

it is the delivery of oxygen to active tissues that is the major limiting factor to VO₂ max

what did a study by Gollnick et al. (1972) show

a weak relationship between the body’s ability to utilise the available oxygen and VO_2max

describe the graded exercise test

• should use large muscle groups

• running/cycling/rowing

• 8-10 minute optimal test length

• direct testing of maximal aerobic power

• increase load stepwise every 1-4 minutes until the subject cannot maintain desired work rate

what is the average VO_2max of active people

~90ml/kg/min

what is the average VO_2max of inactive people

~30-40ml/kg/min

what is the immediate increase in ventilation mediated by

feed forward reflex

what is ventilation rate controlled by

changes mediated by peripheral and central chemoreceptors

at cessation of exercise, what remains elevated until ATP and CP stores return to the norm

ventilation rate

what is the equation for minute ventilation

V_E = V_T X f_B

what is the V_E at rest

6L/min at rest

what does the increase in tidal volume come at the expense of

expiratory and inspiratory reserve volumes

what is the result of increased ventilation on diffusion capacity

increased due to increased blood flow through he lungs and tissue

• from increased systolic blood pressure and changes in blood flow distribution

at what percentage does maximum exercise ventilation increase rapidly

70%

what is VT (ventilation threshold)

the point during exercise at which ventilation starts to increase at a faster rate than VO₂

what does ventilatory threshold reflect

levels of anaerobiosis and lactate accumulation

what is the exercise intensity of the ventilatory threshold for most people

50%-70% of VO₂ max

what is the equation for cardiac output

HR x SR = CO

when does CO plateau

very high work loads

what is CO (cardiac output) a measure of

blood flow per minute

CO increases linearly with the demand for what

more O2

what is HR (heart rate) increase mediated by

increased sympathetic activation of the SA node and decreased parasympathetic output

what is the max heart rate for males

202 -(0.55 x age) = MHR

what is the max heart rate for females

216 -(1.09 x age) = MHR

SV increases linearly with the demand for more what

O₂

when does SV dip

extremes of exercise due to shortened firing time at high HR

what is increased end diastolic volume (preload) from

• sympathetic venoconstriction

• skeletal muscle pump

• respiratory pump

where is decreased afterload from

vasodilation

what does increased SV result from changes in

• cardiac dimensions

• blood volume

• venous return

what are the mechanisms for SV

• enhanced diastolic firing

• greater systolic emptying

• blood volume expansion and reduced resistance to blood flow

• decreased sympathetic drive = slows HR

what is the frank-starling mechanism

increased SV via increased filling and emptying

what is Q (cardiac output)

amount of blood pumped by the heart in 1 minute

what is Q dependent on

• heart rate

• stroke volume

what is the Fick principle

• more effective blood flow distribution

• increased ability of muscle to extract and process O2

• Relatively greater proportion of sub-max Q to high oxidative muscles rather than to low oxidative muscles

what are factors that affect a vO2 difference

• increased capillarisation

• increased capillary to fibre ratio

• increased aerobic capability (mitochondria & respiratory enzymes)

what are the effects of detraining

initially quick and then slow

• initial decrease in VO2 max