Physical Education - Why is his or hers bigger than mine?
Why is his or hers bigger than mine?
To rephrase, we might start by asking, "What are the determinants of VO2
max?" Every cell consumes oxygen in order to convert food energy to useable
ATP for cellular work. Muscle cells that are contracting have high demands
for ATP. So it follows that they will consume more oxygen during exercise.
The sum total of billions of cells throughout the body consuming oxygen and
generating carbon dioxide can be measured as the breath, using a
combination of volume-measuring and oxygen-sensing equipment. So if we
measure a greater consumption of oxygen during exercise, we know that more
muscle cells are contracting and consuming oxygen. To receive this oxygen
and use it to make ATP for muscle contraction, our muscle fibres are
absolutely dependent on two things:
* an external delivery system to bring oxygen from the atmosphere to the
working muscle cells
* mitochondria  to carry out the process of aerobic energy transfer
Endurance athletes are characterised by both a very good cardiovascular
 system and well-developed oxidative capacity in their skeletal muscles.
We need a big and efficient pump to deliver oxygen-rich blood to the
muscles, and we need mitochondria-rich muscles to use the oxygen and
support high rates of exercise. Which variable is the limiting factor in
VO2 max. - oxygen delivery or oxygen utilisation? This is a question that
has created debate among exercise physiologists, but, for most, the jury is
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