the training-induced declines in haemoglobin
concentration and serum ferritin concentration,
have created confusion and controversy about
‘anaemia’ and ‘iron deficiency’ in athletes.
‘Sports anaemia’
A prime ‘Humpty-Dumpty problem’ has been
the failure of some authors to understand or
point out that a ‘low’ or ‘subnormal’ haematocrit
or haemoglobin concentration in a given
athlete—especially an endurance athlete—is not
necessarily ‘anaemia.’ Anaemia is best defined as
asubnormal number or mass of red blood cellsfor a
given individual. In this sense, most endurance
athletes (particularly male athletes) with ‘sub-
normal’ haematocrit or haemoglobin concentra-
tion have not anaemia, but pseudoanaemia.
It is true that athletes, notably endurance ath-
letes, tend to have lower haemoglobin concentra-
tions than non-athletes. This has been called
‘sports anaemia’. Sports anaemia, however, is a
Humpty-Dumpty misnomer because the most
common cause of a low haemoglobin level in an
endurance athlete is a false anaemia. This false
anaemia accrues from regular aerobic exercise,
which expands the baseline plasma volume,
diluting the red blood cells and haemoglobin
concentration. In other words, the naturally
lower haemoglobin level of the endurance
athlete is a dilutional pseudoanaemia.
The increase in baseline plasma volume that
causes athlete’s pseudoanaemia is an adaptation
to the acute loss of plasma volume during each
workout. Vigorous exercise acutely reduces
plasma volume by up to 10–20% in three ways.
First, the exercise-induced rise in systolic blood
pressure and the muscular compression of
venules increase capillary hydrostatic pressure.
Second, the generation of lactic acid and other
metabolites in working muscle increases tissue
osmotic pressure. These two forces, in concert,
drive an ultrafiltrate of plasma from blood to
tissues. Third, some plasma volume is lost in
sweat.
To compensate for these bouts of exercise-
induced haemoconcentration, the body releases
328 nutrition and exercise
renin, aldosterone and vasopressin, which con-
serve water and salt. Also, more albumin is
added to the blood. The net result is an increase
in baseline plasma volume (Convertino 1991).
So baseline plasma volume waxes and wanes
according to physical activity. For example,
if non-athletic men begin cycling vigorously
2 h · day–1, in less than a week, baseline plasma
volume will expand by 400–500 ml. If they then
quit cycling, plasma volume will decline as fast
as it once expanded. Baseline plasma volume can
increase by 10% 1 day after a half-marathon
(Robertsonet al. 1990) and by 17% 1 day after a
full marathon (Davidson et al. 1987). Even a
single brief session of intense exercise can
expand the baseline plasma volume by the next
day. For example, when six athletic men per-
formed eight brief bouts at 85% of V.
o2max.on
a cycle ergometer, baseline plasma volume
decreased by 15% during the exercise session,
but was expanded by 10% 1 day later (Gillen et al.
1991). In short, the endurance athletes who train
the hardest have the highest plasma volumes
and the lowest haemoglobin levels. This is
pseudoanaemia, a facet of aerobic fitness
(Eichner 1992).Training and iron profile
Training, especially endurance training, tends to
decrease the serum ferritin level. For example,
after pilot research found iron deficient profiles
in adolescent female runners during seasons of
cross-country running, Nickerson et al. (1985)
reported the first controlled trial of iron supple-
ments for such runners. Eight (40%) of 20 adoles-
cent female runners given placebo (vs. only one
of 20 given iron supplements) developed ‘iron
deficiency’ (serum ferritin < 20 mg·l–1) after 5 or
10 weeks of the cross-country running season.
No runner developed iron deficiency anaemia.
Adolescentmalerunners, with higher iron
stores, are less apt to develop iron deficient pro-
files. Nickerson et al. (1989) found that 34% of
female but only 8% of male runners ‘developed
iron deficiency’ (ferritin < 12 mg·l–1and transfer-
rin saturation <16%) during a season. Two girls