OXYGEN UPTAKE AT REST, DURING PHYSICAL ACTIVITY AND DURING RECOVERY Flashcards
what are the three phases?
Phase 1: oxygen deficit
Phase 2: steady state
Phase 3: EPOC
INCREASED OXYGEN UPTAKE
Oxygen uptake (VO2) refers to the amount of oxygen transported to, taken up by and used by the bodies for energy production. At rest, the body consumes oxygen at a rate of approximately 0.25 litres per minute. However, when exercise begins, oxygen uptake is the working muscles use more of the oxygen made available by the combined efforts of the circulatory and respiratory systems.
- There is a linear relationship between oxygen uptake and exercise intensity
OXYGEN UPTAKE AT REST
When at rest, the body’s need for ATP is relatively small, requiring minimal oxygen consumption.
- At rest the average person consumes about 0.3L of oxygen per minute and will usually use a mixture of CHO and fats for energy.
PHASE ONE: OXYGEN DEFICT
(Def): O2 deficit is the state where there is a shortfall of oxygen consumption and use.
—> When exercise begins, oxygen uptake increases as the body attempts to meet the increased oxygen demand of the working muscles that results from their need to produce more energy for ATP resynthesis.
- The respiratory and cardiovascular systems play the major role when increasing oxygen uptake and transport to the working muscles.
However, any time during exercise performance when intensity increases, there is a discrepancy (shortfall) between the required amount of oxygen and the oxygen supplied.
The oxygen deficit occurs because the respiratory and circulatory systems take some time to adjust to the new oxygen demand (even at low exercise intensities). Therefore, this displays the mount of oxygen supplied lags behind the amount needed until these systems make the necessary adjustments required to increase oxygen supply.
PHASE TWO: STEADY STATE
(Def): steady state is the state which oxygen demand = oxygen supply
—> It may take anywhere between a few seconds and 1 minute or more, depending on the intensity of the exercise, for oxygen supply or uptake to increase sufficiently to meet the oxygen demands of the exercise
- If and when oxygen supply does equal the oxygen demand of the exercise, an aerobic steady state is attained. The increased supply in oxygen enables a greater proportion of ATP to be resynthesised aerobically.
However, if the exercise intensity increases again, the demand for ATP resynthesis and oxygen also increases.
PHASE THREE: EXCESS POST-EXERCISE OXYGEN CONSUMPTION (EPOC)
After the cessation of exercise, oxygen uptake or consumption does not immediately return to resting levels. Rather, oxygen consumption remains temporarily elevated. This elevated oxygen consumption, which exceeds that normally experienced at rest, is referred to as excess post-exercise oxygen consumption (EPOC).
Factors responsible for elevated EPOC:
A number of factors associated with EPOC, and they can only be understood by looking at the chemical and physical changes that occur in muscle cells during exercise. These changes increase the levels of oxygen consumption and ATP, and they continue for some time after exercise has ceased, including during the recovery phase, when oxygen consumption remains elevated.
The factors associated with the amount and duration of EPOC include:
· elevated muscle temperature
· increased use of mitochondria
· increased ATP production
· restoring CP stores
· lactate production during exercise.
FACTORS AFFECTING MAXIMUM OXYGEN UPTAKE
Maximum oxygen uptake, orVO2max, represents the maximum amount of oxygen that can be taken up by, transported to and used by the body for energy production
- body size
- gender
- genetics
- training status
BODY SIZE
Oxygen uptake is related to body size; a larger, heavier person requires more oxygen than a smaller person. It is for this reason that VO2max is usually expressed relative to body size in mL/kg/min — so that individuals can be compared, particularly in relation to their aerobic fitness levels, irrespective of differences in body size.
GENDER
Females tend to have lower oxygen uptake than males of a similar age and athleticism. For untrained individuals can be as great as 20-25% less. Females tend to have a higher amount of body fat and lower muscle mass. Body fat doesn’t use oxygen.
Females have lower blood volumes and lower levels of red blood cells and haemoglobin. Therefore less oxygen carrying capacity. Females typically have smaller lung size and volume.
GENETICS
Aerobic capability is largely genetically determined. Up to 25-50% of variance. Training can still largely improve VO2 max.
TRAINING STATUS
Aerobic training can substantially increase maximum oxygen uptake values for both males and females.
- Aerobic training can substantially increase VO2 max
- Average VO2 max for untrained adult male 20-29 is 43-52 mL/kg/min.
- Average VO2 max for untrained adult female 20-29 is 33-42 mL/kg/min.
- Trained endurance athlete can be up to 50-75 mL/kg/min.
AGE
Maximum oxygen uptake tends to decline with increasing age. It peaks during late adolescence and early adulthood and then declines from that point. The average rate of decline is generally accepted to be about 1 per cent per year or 10 per cent per decade after the age of 25. However, training and/or maintaining a physically active lifestyle can both increase maximum values and decrease the rate of decline that occurs with increasing age.
