OvertrainingNutritional Intervention

Chapter 37
Overtraining: Nutritional Intervention
HARM KUIPERS
Introduction
The primary goal of athletic training is to
enhance performance and to peak at the right
moment. To push the performance capacity to its
upper limit, relatively high amounts of intensive
exercise are assumed to be necessary. Consequently, athletes are often balancing on the edge
between training and overtraining. One of the
most difficult parts of the training process is to
find the optimal balance between training and
recovery. A correct balance between training and
recovery is of utmost importance, since the difference between winning and losing is small.
Snyder and Foster (1994) reported that in the
1988 Olympic speedskating event in Calgary, the
difference in average velocity between all gold
and silver medal performances was 0.3%, while
the mean difference between all the gold medalists and the fourth places was 1.3%. Similar differences can be found in other sports.
Unfortunately, few scientific data exist about
the optimal amount of training for peak performance. The relatively scarce data available
indicates that there appears to be an inverted Ushaped relationship between training volume
and increase in performance. It is assumed that
there is an optimal amount of training which will
yield optimal performances (Fig. 37.1). However,
this optimal amount of training is poorly
defined, and passing this ‘gray’ area may lead to
overtraining. Proper nutrition, consisting of adequate carbohydrate intake, may enhance recovery, and consequently may play a significant role
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to optimize the training process by increasing the
training loads that can be sustained.
The actual adaptation concludes the recovery
phase and, therefore, recovery is one of the most
important components of the training process.
Too many athletes and coaches lay too much
emphasis on the training but pay too little attention to recovery. Although little is known about
recovery, it appears that the time required for
the recovery phase is not always the same and
depends among other things on several factors,
such as: the volume of training, individual
factors, and nutrition. It has been shown that
after exercise, glycogen synthesis can be optimized by starting to consume easily absorbable
carbohydrates immediately after exercise in an
amount of 1–2 g · kg–1 body weight. Although
direct evidence is still lacking, carbohydrate
intake may indirectly also enhance other components of the recovery process. Carbohydrate
ingestion stimulates insulin secretion, which is a
powerful stimulator of protein synthesis, one of
the key processes for recovery and adaptation.
When exercise and the concomitant disturbance in homeostasis are not matched by adequate recovery, an athlete is actually overdoing
or overtraining, and may become overloaded or
overtrained. In order to obtain optimal results in
sports, it is important to detect too much training
or incomplete recovery as soon as possible.
Although overtraining is a general term, it may
include different entities. Based on the pathogenesis and affected organ systems, three different
types of overtraining can be distinguished:
Performance
overtraining: nutritional intervention
493
Overreaching
2 ADP
1 ATP +1 AMP
Optimal training
NH3
Undertraining
Overtraining syndrome
Training load
Fig. 37.1 The relationship between training volume
and increase in performance capacity. Courtesy of
C. Foster.
1 Mechanical overtraining.
2 Metabolic overtraining or overreaching.
3 Overtraining syndrome or staleness.
Mechanical overtraining
Mechanical overload involves the locomotor
system. An imbalance between exercise and
recovery is usually local and is generally
expressed as an overuse injury. Although little
information is available about the role of nutrition in these injuries, there is some indication
that a low calcium intake increases the risk
for stress injuries to the skeleton. Another type
of mechanical overtraining is exercise-induced
muscle damage. Muscle damage is associated
with inflammatory changes, which are followed
by regeneration. There is some evidence that a
deficit in vitamin E intake may increase the susceptibility to this type of mechanical damage.
However, athletes who consume a normal mixed
diet are unlikely to have a vitamin E deficiency.
Therefore, supplementation of vitamin E in these
athletes does not provide any protection against
exercise-induced muscle soreness.
Metabolic overtraining or overreaching
Nowadays athletic training includes a high
volume of intensive exercise. Intensive exercise
relies on carbohydrate supply, resulting in a
IMP
Uric acid
Fig. 37.2 Metabolic pathway indicating the
breakdown of ADP to uric acid, under the formation of
ammonia. IMP, inosine monophosphate.
rapid depletion of glycogen stores. When highintensity exercise is done in association with low
glycogen levels, this may lead to an imbalance
between the rates of adenosine triphosphate
(ATP) splitting and ATP generation. This in
turn will lead to an accumulation of adenosine
diphosphate (ADP). In order to restore the
ADP/ATP ratio, 2 ADP form 1 ATP and 1 adenosine monophosphate (AMP), which is further
broken down to inosine monophosphate and
eventually to uric acid (Fig. 37.2), while ammonia
is also formed (Sahlin & Katz 1993). When insufficient time for recovery is allowed, this may lead
to a decline of the energy-rich phosphate pool.
The metabolic type of overtraining is probably
associated with overreaching.
Data suggest that insufficient carbohydrate
intake may enhance the susceptibility for developing overreaching. Therefore, adequate carbohydrate intake and quick restoration of glycogen
stores may decrease the risk of developing metabolic overtraining. Studies have shown that a
high carbohydrate intake, starting immediately
after exercise, may restore glycogen stores within
24 h. However, although insufficient carbohydrate intake may increase the susceptibility for
metabolic overtraining, a high intake of carbohydrate may decrease the risk, but cannot prevent
metabolic overtraining. Therefore, in addition to
proper nutrition, adequate rest and recovery are
of paramount importance.
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practical issues
Overtraining syndrome or staleness
When the central nervous system cannot cope
any more with the total amount of stress, a dysfunction 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 characterized 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 function (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 glutamine levels may lead to decreased immune
function. Further research is needed to determine whether supplementation of glutamine can
decrease the risk of overtraining or can ameliorate 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, nutritional deficiencies, and jet lag. Nutritional deficiencies 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 overtraining 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 branchedchain amino acids. This, in turn, would lead to an
increased uptake of tryptophan in the brain and
an increased formation of the neurotransmitter
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 branchedchain 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 sympathetic, 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 overtraining 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 parasympathetic 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 syndrome is most often observed in team sports and
sprint events, while the parasympathetic form is
overtraining: nutritional intervention
preferentially observed in endurance athletes
(Lehmann et al. 1993). The characteristics of the
parasympathetic form of the overtraining syndrome are misleading to the athletes and the
coach, because the symptoms are suggestive of
excellent health. Although the pathophysiological mechanism of both forms of overtraining is
not clear yet, it is hypothesized that both forms
reflect different stages of the overtraining syndrome. The sympathetic form is supposed to be
the early stage of the overtraining syndrome,
during which the sympathetic system is continuously activated. During advanced overtraining,
the activity of the sympathetic system is inhibited, resulting in a dominance of the parasympathetic system. This would also explain the
increased proneness for hypoglycaemia during
exercise in the parasympathetic form, because
glucose counter-regulation is mediated via the
sympathetic system.
Because overtraining is difficult to diagnose, it
is most important to prevent overtraining. The
following rules and advice can be helpful to
prevent overtraining.
1 Develop a well-balanced, flexible and attractive training programme, with individual adjustment when necessary.
2 Have field or laboratory performance tests at
regular intervals — for instance, during the easy
week during periodization.
3 Emphasize proper diet, which supplies sufficient carbohydrate to meet the metabolic requirements (4–8 g · kg–1 body weight during normal
training and up to 10 g · kg–1 body weight during
heavy training) and also provides sufficient
amounts of other nutrients.
4 Have the athletes keep a training log in which
resting heart rate and body weight are registered.
Because behavioural signs seem to be the first
consistent signs of overtraining, it can be helpful
to use the profile of mood states scale (POMS
scale) as described by Morgan and coworkers
(1987). The POMS scale yields information about
the global measure of mood, tension, depression,
anger, vigour, fatigue and confusion. By monitoring the mood state on the POMS scale, overtraining can be detected at an early stage.
495
In addition, or alternatively, the athletes can fill
in a self-designed visual analogue scale questionnaire, containing questions about fatiguability,
recovery, motivation, irritability and sleep.
Recent research has shown that a balanced
training programme results in an increase in
plasma glutamine concentrations, whereas a
mismatch between training and recovery is associated with a decline in plasma glutamine concentrations (Rowbottom et al. 1996). Therefore,
monitoring plasma glutamine concentrations
during the training process may be helpful to
detect overtraining in its earliest stage. However,
more studies are needed to provide clear and
practical guidelines about this possibility.
Treatment of overtraining
When symptoms of increased fatiguability occur,
and no other symptoms are observed, overreaching or metabolic overtraining is most likely. In
that case, the training should be adjusted, mainly
by decreasing the volume.
A decrease in volume is the most important
measure to be taken. Most emphasis should be
laid on sufficient rest, recovery, and a diet that is
rich in carbohydrates and contains sufficient
amounts of trace elements, vitamins, and other
nutrients (Kuipers & Keizer 1988). Usually metabolic overtraining is reversible within some days.
Systemic overtraining or overtraining syndrome usually requires one to several weeks for
recovery. The contributing factors should be
identified and sometimes counselling is necessary. There are no specific drugs or treatments
known. Although proper nutrition is important,
there is no evidence that specific nutritional supplements may be of any help to treat overtraining
or to enhance recovery.
References
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