Provide anatomy and
physiology advice to clients
Respiration an exercise
Respiration and exercise
• The amount of oxygen that we use is regulated
by the metabolic rate of our cells. It has been
calculated that whilst we are at rest we use
about 250ml of oxygen each minute. However,
when we exercise our oxygen need can
increase ten times (say 2500 ml per minute) and
in high intensity exercise the increase may be
perhaps as much as 20 times. When we
exercise we engage more muscle cells in work
and the oxygen demand to drive ATP synthesis
in these cells obviously increases.
Respiratory physiological changes
with exercise
• We have seen how training can increase cardiac output
through strengthening the ventricular wall muscles and
therefore increasing the stroke volume. Long term
exercise can also increase the amount of oxygen
inspired, by strengthening the diaphragm and intercostal
muscles which in turn allow for more lung expansion.
Both of these effects when combined increase the
difference in oxygen pressure between the lungs and the
lung capillaries which in turn permits more oxygen to
enter the capillaries. Oxygen supply is the limiting factor
in the amount of work that our muscles can do, so it is
important that if person wants to increase the capacity of
their muscles to work, then they need to increase the
amount of oxygen that can be supplied.
Mitochondrial changes
• When we train our body can recognise the need for more
oxygen so in response it manufactures more
mitochondria in muscle cells. But the capacity of the
heart to increase its stroke volume is limited, although
the number of red blood cells can increase with training.
The net result of this is that it is the lung that regulates
our ultimate capacity to do work, and if the lungs are not
functioning optimally, then our capacity to work harder in
exercise is limited. An understanding of lung capacities
is therefore important for those interested in fitness
instruction.
The notion of respiratory volume
• The amount of air that we breathe
obviously varies between people but also
varies according to the conditions
prevailing for a person at any time. It is
useful for a fitness instructor to know
about these volumes and some of the
changes that might be expected during an
exercise regime.
The tidal volume
• This is the amount of air that moves in and
out of the lungs with each breath. It
ranges between 500ml and 1000 ml
across the population. The tidal volume
can increase with exercise as the capacity
of the lungs increases with exercise
training. All the lung capacities may be
measured by a spirometer.
Inspiratory Reserve Volume
• The amount of air that can be inspired
forcibly beyond the tidal volume is called
the Inspiratory Reserve Volume. This
ranges from about 2000 to 3000ml across
the population.
Expiratory Reserve Volume
• The Expiratory Reserve Volume is the
amount of air that can be evacuated from
the lungs after a tidal expiration. So, if you
breathe out normally then evacuate the
lungs, this is the Expiratory Reserve
Volume. It is normally about 1200ml.
Residual Volume
• Even after you blow out all the expiratory
reserve volume the lungs still have air in
them. This is called the Residual Volume
and is about 1200ml. The job of residual
air is to keep the alveoli open and this
prevents lung collapse.
Respiratory Capacities
• These consist of two or more lung
volumes: the Inspiratory Capacity, the
Functional Residual Capacity, the Vital
Capacity and the Total Lung Capacity.
Inspiratory Capacity
• This is the total amount of air that can be
inspired after a tidal expiration, so it is
equal to the Tidal Volume plus the
Inspiratory Reserve Volume.
Functional Residual Capacity
• The Functional Residual Capacity in the
sum of the Residual Volume and the
Expiratory Reserve Volume.
Vital Capacity
• The Vital Capacity of the lungs is the total
amount of exchangeable air. This is the
sum of the Tidal Volume, Inspiratory
Reserve Volume and Expiratory Reserve
Volumes.
Total Lung Capacity
• Total Lung Capacity is the sum of all
volumes and is about 6 litres in healthy
people. A table giving all these volumes
and capacities is on this slide.
Exercise and Pulmonary Changes
• Whilst we are relaxed we breath about 12 times a minute
and the tidal breath is about 500ml so that equates to
6000ml of air per minute. Now as we start to exercise
our breaths become more frequent, even up to 50 per
minute and they become deeper. In fact, the frequency
of our breathing increases before we actually start to
exercise. Our inspiratory centre controls our breathing
rate in exercise and this in turn is controlled by the
amount of lactate and other metabolic by products. But
as we’ve seen earlier, the major respiratory changes due
to exercise arise from increases in our tidal volume and
the amount of oxygen that can diffuse from the lungs into
the capillaries.
Oxygen debt
• Muscles have glycogen stores that allow them to
contract for up to several hours and after that they can
call on fat supplies to provide ATP. Now during
anaerobic contraction oxygen is not required, but an
oxygen debt results because oxygen still must be used
to deal with the by products of anaerobic metabolism.
So if you run 100 metres very quickly then you will need
oxygen when you’ve finished. The high levels of lactic
acid in your blood trigger the respiratory centre of your
brain to make you breathe very deeply and gulp air. As
you train and become fitter your oxygen carrying
capacity improves and you therefore “puff” less after
anaerobic exercise.
VO2 Max
• VO2 max is the highest rate at which oxygen can be
taken up and utilised during exercise. It is expressed as
the amount of oxygen per kilogram of body weight per
minute. It is largely determined by a person’s genetics
but can be improved slightly by exercise. The oxygen
uptake and carbon dioxide output are measured whilst a
person is submitted to exercise such as a treadmill. The
exercise intensity increases until the person is
exhausted. Elite male athletes have VO2 max levels
around 80 ml/Kg/min and females about 70. Fit young
people may have VO2 max levels around 45 for males
and 40 for females. These all decrease with age.