explanation is that although running tends to
have a somewhat anorexic effect, especially in
the few hours after exercise, swimming may
have an opposite effect by stimulating appetite
(Harri & Kuusela 1986). This would imply that
swimmers tend to increase their energy con-
sumption in parallel with their training where
runners may not. To this author ’s knowledge,
there have been no published studies comparing
the effects of running and swimming on the
postexercise appetite. Under this assumption
of increased appetite in swimmers, swimmers
would not be expected to lose a great deal of
body fat during their training. A study by
Johnson et al. (1989) with female university
swimmers supports this argument since no
changes in body composition were observed
over a 25-week season of training. In contrast,
however, Barr et al. (1991) reported decreased
body fat, increased lean body mass, and no
change in body weight in male college swimmers
training 22 000 m · week–1 during a 25-week
season. In agreement with this study showing
changing body composition in males during
swim training is a study by Meleski and Malina
(1985) showing decreased body weight,
decreased absolute and relative fat mass, and
increased lean body mass in a group of female
college swimmers during the first 2 months of a
training season.
Another explanation that has been proposed
for the higher body fat percentages in competi-
tive swimmers is a possible difference in fuel uti-
lization both during and following the exercise
that promotes fat storage in swimmers. As
support for this argument, some have pointed to
studies of cold exposure which is known to
stimulate fat storage both in animal models and
in humans. To determine if swimming training
alters fuel utilization and the hormonal milieu
differently from running, Flynn et al. (1990)
monitored energy expenditure and fuel utiliza-
tion of eight male swimmers and runners while
exercising at 75% of maximum oxygen uptake
and during 2 h of recovery. Although the energy
cost of recovery was similar between the two
exercise modes, the respiratory exchange ratio
results suggested increased fat oxidation after
swimming compared with running. In contrast,
serum glycerol concentration was elevated to a
greater extent after running than after swim-
ming, suggesting enhanced mobilization of
triglycerides with running. Whether this differ-
ent response can account for the differences in
body composition between runners and swim-
mers remains to be studied.Carbohydrate needs in training
The high volume and intensity of swimmingswimming 611
Fig. 46.1Swimmers favour high
training volumes. This means that
a high energy intake is essential,
but opportunities for eating may
be limited when long training
sessions must be combined with
work or study. Photo © Allsport.