completely saturated with O 2 obtained from
the alveoli. It should be noted that, at the high-
est levels of oxygen uptake, highly trained
endurance athletes (e.g. distance runners and
cross-country skiers) show a lowered oxygen
saturation in arterial blood. This is taken to indi-
cate that the blood flow through the lungs during
such intense aerobic exercise for these athletes
exceeds the capacity of the ventilatory system to
provide oxygen to the lungs.
As will be discussed, maximum aerobic power
(V
.
o2max.) can be increased mainly by increasing
the stroke volume capability of the heart,
which increases the minute volume capability.
Maximum heart rate does not increase with
aerobic conditioning but, actually, it either
remains the same or decreases.
TheV
.
o2max.of 4.5 l · min–1corresponds to a
metabolic power production of 1500 W. As the
athlete in the example is capable of power pro-
duction for short periods (e.g. 1–20 s) in the range
of 3000–6000 W, the question could be raised as to
what values for the circulatory variables would
be expected during such exercise performance.
The answer is that these values, if measured,
would be irrelevant. The athlete would be per-
forming in the range of power production where
oxidative (aerobic) metabolism contributes little
or no energy and the muscles will rely on ATP,
PCr and anaerobic glycolysis.
Adaptations to conditioning
The adaptations of the human organism to pro-
grammes of exercise conditioning are highly spe-
cific to the exercise programme (i.e. the stimulus)
provided. Adaptations to resistance training for
strength, to anaerobic training (as in sprinting)
and to endurance (aerobic) training are very dif-
ferent and, if used inappropriately, can actually
serve to be counterproductive.
Aerobic conditioning
For athletes engaged in events lasting approxi-
mately 3 min or longer, aerobic conditioning is a
crucial factor in preparing for competition (Fig.
12 nutrition and exercise
1.5). For events lasting between 1 and 3 min,
aerobic conditioning is important but anaerobic
sources of energy for the power demands
become more important the higher the exercise
intensity and the shorter the accompanying per-
formance time. It also makes a great difference
whether or not the athlete performs to exhaus-
tion (such as in the 10-km run) or is involved in
one half of a soccer match (45 min) which
involves a wide range of aerobic/anaerobic
intensities and intermittent activity. Also, skill
may be more important than any other perfor-
mance consideration.
If an increase in aerobic power is required, the
athlete must follow a programme designed to
increase the cardiac output capability (SV andFig. 1.5A sport such as road cycling depends
predominantly upon aerobic metabolism. Photo ©
Allsport / M. Powell.