Acute Physiological Responses to Exercise

What is Oxygen Uptake (VO2)?

The amount of oxygen transported to, taken up by, and used by the body for energy production.

What is the relationship between oxygen uptake and exercise intensity?

There is a linear relationship that continues until a maximal level of oxygen uptake is attained, known as VO2 Max.

What is VO2 Max?

The maximum amount of oxygen per minute a person can use during intense exercise.

What is the formula for calculating VO2 Max?

VO2 Max = Q (cardiac output) x a-vO2 difference.

Factors that affect VO2 Max

Body size (Larger heavier people require more oxygen than smaller lighter people)

Gender (Females tend to have a higher body fat percentage which doesn't consume oxygen. Females have reduced oxygen carrying capacity of the blood. Females generally have smaller size and volume of lungs & heart, reducing their oxygen intake and transport capacity)

Genetics (Genes may account for 25-50% of the variances)

Age (Maximum oxygen uptake peaks in early adulthood and then declines about 1% a year)

Training Status (increases the efficiency of oxygen transport within the body, a stronger heart can pump more blood)

What are the two ways to measure oxygen uptake?

Absolute (litres of oxygen per minute) and Relative (ml of oxygen per kilo of body weight per minute).

Stages of Oxygen Uptake

1. Oxygen deficit

2. Steady State

3. EPOC

What is oxygen deficit?

A period where oxygen supply does not equal oxygen demand, occurring during increased exercise intensity.

What is steady state in terms of oxygen uptake?

When oxygen supply equals oxygen demand.

What is EPOC?

Excess Post-exercise Oxygen Consumption, when oxygen consumption remains above resting level after exercise.

Fast replenishment phase - replenish pc stores

Slow replenishment phase - remove metabolic by-products such as hydrogen ions and regulates and decrease body temperature

Respiratory Response

Ventilation increase (VE)

Tidal volume increase (TV)

Respiratory rate increase (RR)

Ventilation

air breathed in & out per minute, formula (VE = TV x RR)

Tidal volume

amount of inspired & expired air per breath

Respiratory rate

number of breaths per minute

Pulmonary diffusion

movement of gas from the area of high concentration to low concentration, occurs at alveoli capillary interface

Traits of Ventilation (mention rest and maximal levels)

Increases during exercise

At rest, average is 5-6 litres

During maximal exercise, for males can increase beyond 180 litres per minute and for females 130

Traits of Tidal volume

Increases during exercise

At rest, average is 0.5 litres

Can get as high as 3-5 litres under maximal workloads

Traits of Respiratory rate

At rest, average is 12 breaths per minute

Can get as high as 35-50 breaths per minute

Traits of Pulmonary diffusion

Increased diffusion allows greater amounts of oxygen and carbon dioxide to be exchanged

More oxygen available to working muscles

Greater removal of carbon dioxide (by-product of aerobic energy production).

Increases by up to three times during exercise

Cardiovascular responses

Heart rate increased

Stroke volume increased

Cardiac Output increased

Blood pressure increased

Redistribution of blood to working muscles

Arteriovenous oxygen difference increase

Heart rate (HR)

number of beats per minute

Traits of Heart rate

Increases directly proportional to exercise intensity

Stroke Volume (SV)

amount of blood ejected from the left ventricle with each contraction

Trait of Stroke volume

Stroke volume will increase during exercise but plateau at approx 40-60% of max heart rate, then it will plateau

Cardiac volume (Q)

amount of blood pumped out of the left ventricle per minute, formula (Q (L)= HR (bpm) X SV (mL))

Traits of Cardiac volume

Cardiac output increases during exercise due to increased heart rate and stroke volume

highly trained athletes are capable of achieving significantly higher cardiac output levels compared to average adults

Blood pressure

the pressure exerted against the arterial walls as it is forced through the circulatory system

Traits of Blood pressure

Systolic pressure - measures the pressure in your arteries when your heart beats

Diastolic pressure - measures the pressure in your arteries when your heart is relaxed

During dynamic whole body exercise (running, swimming), systolic pressure will increase whilst diastolic remains relatively unchanged.

During resistance based exercises, both systolic and diastolic blood pressure increase

Redistribution of blood to working muscles

Blood flow is redirected away from less active organs (liver, kidneys) and towards skeletal muscle, due to increased demand for oxygen by the working muscle during exercise

Traits of blood redistribution

15-20% of blood flow to muscles at rest

80 - 85% of blood flow to muscles during exercise

Arteriovenous oxygen difference (AVO2 diff)

difference in oxygen concentration in arteries compared to veins

Traits of Arteriovenous oxygen difference (AVO2 diff)

It is measured in ml of O2 / 100ml of blood

At rest, AVO2 diff is small, approximately 5 mls per 100 mls of blood due to the low demand for oxygen by the muscles

During exercise, AVO2 diff can increase up to 15-18ml per 100m of blood. This is due to the muscles extracting and using more oxygen, thus leaving a greater difference.

Muscular responses

F.O.R.T.E.W

Fuel usage

Oxygen consumption

Recruitment of motor units

Temperature Increase inside the body

Enzyme activity

Waste production

Traits of Fuel usage

Fuel Usage increases, therefore fuel stores deplete (ATP, PC, Muscle Glycogen, Triglycerides)

Traits of Oxygen consumption

During aerobic exercise, muscle cells require more ATP to meet the increased energy demand. To produce more ATP aerobically, muscles extract and utilize more oxygen from the bloodstream.

This increased oxygen uptake by the muscles leads to a greater arteriovenous oxygen difference (a-vO₂ diff)

Traits of Recruitment of motor units

Anaerobic

During exercise, an increase in motor unit recruitment must occur so that more muscle fibres are activated to contract

Traits of Temperature inside body

Aerobic

Increased blood flow to the muscles, coupled with the heat generated as a by-product of the increased production of ATP during exercise, results in an increase in muscle temperature.

Traits of Enzyme Activity

both anaerobic and aerobic

enzyme activity increases to speed up chemical reactions

Traits of Waste production

Waste production increases, both Pi and H+ ions will inhibit muscular contraction and decrease performance