section is concerned with the issue of what happens when people’s exercise habits
become excessive, compulsive or otherwise maladaptive. Therefore, we shall now
consider briefly two health hazards that are associated with exercise behaviour—namely,
“overtraining” and “exercise dependence”. Although the symptoms of these problems are
similar, there is one important difference between the conditions. Briefly, whereas the
former difficulty is largely confined to sports performers, exercise dependence can also
occur in non-athlete populations (Buckworth and Dishman, 2002).
It has long been known that intensive training regimes do not always enhance athletic
performance. More precisely, when the nature, intensity and/or frequency of athletic
training exceed the body’s adaptive capacity and lead to a deterioration in sport
performance, then “overtraining” has occurred (Cashmore, 2002). Commonly regarded as
a generalised stress response of the body to an extended period of overload, overtraining
may be defined as “an abnormal extension of the training process culminating in a state
of staleness” (Weinberg and Gould, 1999, pp. 434–435). Other terms for this syndrome
include “staleness”, “burnout” and “failing adaptation” (Hooper, Traeger Mackinnon,
Gordon and Bachman, 1993). A theoretical model of this state was proposed recently by
Tenenbaum, Jones, Kitsantas, Sacks and Berwick (2003).
In general, overtraining has been attributed to a combination of excessive levels of
high-intensity training and inadequate rest or recovery time. Although no single,
universally agreed diagnostic index of this problem exists, a host of typical physiological
and psychological symptoms have been identified. For example, physiological signs of
overtraining include suppressed immune function (with an increased incidence of upper
respiratory tract infection), increases in resting heart rate, decreases in testosterone and
increases in cortisol concentration and decreases in maximal blood lactate concentration.
Similarly, apart from a deterioration in athletic performance, common psychological
symptoms of this disorder include mood disturbances, feelings of chronic fatigue, loss of
appetite, repetitive loading injuries (e.g., shin-splints) and sometimes insomnia
(Cashmore, 2002; Morgan, Brown, Raglin, O’Connor and Ellickson, 1987). The
prevalence of this syndrome can be gauged from the claim by Morgan (2000) that over
50 per cent of all elite male and female marathon runners have overtrained in their
careers.
Paradoxically, overtrained athletes tend to perform progressively worse as they try
harder. We encountered this phenomenon of diminishing returns in sport performance
earlier in this book in the section on “choking” (Chapter 3). But overtraining differs from
choking because it appears to be caused by factors other than excessive anxiety. In
particular, these factors include inadequate recovery time between bouts of training,
prolonged or over-intense training regimes, personal problems and inadequate coping
resources (Weinberg and Gould, 1999). Unfortunately, although overtraining has been
recognised by sports scientists for decades, little research has been conducted on the
putative psychological mechanisms underlying this problem. Nevertheless, one
mechanism that has been proposed in this regard is mood state. Thus Morgan (2000)
claimed that mood disturbance in athletes (as measured by the Profile of Mood States,
POMS; McNair et al., 1992) may be causally related to overtraining. Unfortunately, this
speculation has received only limited empirical scrutiny. As a result, little theoretical
progress has been made in understanding either the precise causes of this problem or the
best way to overcome it. Despite the fact that this state is poorly understood, its very
Sport and exercise psychology: A critical introduction 226