Overtraining syndrome or staleness
When the central nervous system cannot cope
any more with the total amount of stress, a dys-
function of the neuroendocrine system and
changes in behaviour may be encountered
(Barron et al. 1985). This generalized form of
overstress in athletes is generally referred to as
overtraining syndrome or staleness (Kuipers &
Keizer 1988). The overtraining syndrome is char-
acterized by premature fatigue during exercise,
decline in performance, mood swings, emotional
instability, and decreased motivation (Stone et al.
1991). In addition, overtraining and staleness
may be associated with changes in immune func-
tion (Fry et al. 1992). The proneness for infections
has been attributed to changes in glutamine
metabolism by Newsholme and associates
(1991). They suggested that intensive exercise
may cause a decrease in plasma glutamine.
Since glutamine is considered to be essential for
immune cell functioning, decreased plasma glut-
amine levels may lead to decreased immune
function. Further research is needed to deter-
mine whether supplementation of glutamine can
decrease the risk of overtraining or can amelio-
rate the intensity of the symptoms.
Training alone is seldom the primary cause of
overtraining syndrome or staleness. It is rather
the total amount of stress exceeding the capacity
of the organism to cope. Contributing factors for
an overtraining syndrome include: too many
competitions, too much training, infectious
diseases, allergic reactions, mental stress, nutri-
tional deficiencies, and jet lag. Nutritional defi-
ciencies refer specifically to a low carbohydrate
intake. Several studies have shown that even
elite athletes may consume a suboptimal diet,
containing too little carbohydrate and too much
fat. Newsholme et al. (1991) attributed the over-
training syndrome to an increased uptake of
branched-chain amino acids by muscle tissue
during exhaustive exercise, leading to changed
balance of the ratio of aromatic to branched-
chain amino acids. This, in turn, would lead to an
increased uptake of tryptophan in the brain and
an increased formation of the neurotransmitter
494 practical issues
5-hydroxytryptamine. This is supposed to be
associated with central fatigue and symptoms of
overtraining syndrome. However, recent studies
do not provide scientific evidence in support of
this hypothesis (Rowbottom et al. 1995; Tanaka
et al. 1997). In a recent study by van Hall et al.
(1995), in which the ratio between branched-
chain amino acids and aromatic amino acids was
restored by nutritional intervention, no changes
in performance and perception of fatigue were
found.
The German literature distinguishes between
two forms of overtraining: the sympathetic and
the parasympathetic (Israel 1958). The sympa-
thetic, or Basedowian, form is characterized by
increased sympathetic tone in the resting state,
while in the parasympathetic, or Addisonoid,
form the parasympathetic tone dominates in the
resting state as well as during exercise. The main
characteristics of the sympathetic form of over-
training are:- increased resting heart rate;
- slow recovery after exercise;
- poor appetite, weight loss;
- mental instability, mood swings and
irritability; - increased blood pressure in the resting state;
- menstrual irregularities, oligomenorrhoea or
amenorrhoea in females; - disturbed sleep: difficulties in falling asleep
and early wakening; - increased resting diastolic and systolic blood
pressure.
The main characteristics of the parasympa-
thetic form of overtraining are: - low or normal resting pulse rate;
- relatively low exercise heart rate;
- fast recovery of heart rate after exercise;
- hypoglycaemia during exercise, good
appetite; - normal sleep, lethargy, depression;
- low resting blood pressure;
- low plasma lactates during submaximal and
maximal exercise (lactate paradox).
The sympathetic form of overtraining syn-
drome is most often observed in team sports and
sprint events, while the parasympathetic form is