Introduction
The ability to resist fatigue is an important aspect
of many types of sporting activity, whether it be
short-term, high-intensity anaerobic type work,
or longer, high-intensity endurance activity. Ath-
letes who fatigue early do not perform as well as
those who fatigue more slowly, so, in order
to maximize performance, it is important that
fatigue is minimized wherever possible.
Fatigue is generally defined as the failure to
maintain an expected or required force or power
output (Edwards 1981). The causes of fatigue are
multifaceted (see Green 1990 and Hultman et al.
1990 for reviews) and can be roughly divided
into either physiological or psychological. In the
physiological realm, fatigue can be described as
either central or peripheral (Green et al.1987). In
the latter case, there is a myriad of factors
which can interact to decrease power output and
hinder performance. During high-intensity work
of short duration, potential contributors to
fatigue could be related to muscle energy pro-
duction (for example, a decline in muscle adeno-
sine triphosphate, ATP) or they could be related
to impaired electrochemical events of muscle
contraction/relaxation production. Alterna-
tively, fatigue could be related to the accumula-
tion of metabolites—for example lactate,
hydrogen ions and ammonia. During prolonged
submaximal effort, energy substrate depletion
is generally regarded as the major cause of
fatigue, but a number of other factors such as
hyperthermia, dehydration and oxygen trans-
port problems may also contribute in differing
amounts.
Athletes and their coaches have always sought
ways to improve performance and overcome the
fatigue process. In doing so, they have targeted
a number of different areas, including training
methodology, nutritional practices, medical
interventions and the use of both legal and
illegal drugs—for a review of ergogenic aids, see
Chapter 26. With a ‘win at all costs’ mentality,
many athletes have ingested substances which
are claimed to have an ergogenic effect by over-
coming the fatigue process. Over the last decade
or so, the use of sodium bicarbonate and sodium
citrate have become popular to offset fatigue
during short-term, high-intensity exercise. It is
claimed that these substances improve perfor-
mance by buffering the acids which are pro-
duced during exercise.
The aim of this chapter is to discuss the current
knowledge with respect to metabolic acidosis
during both short-term, high-intensity and
endurance exercise and the effects of sodium
bicarbonate and sodium citrate ingestion on
these types of performance.Basics of acid–base balance
Substances that release H+when they dissociate
in solution are called acids, whereas substances
that accept H+ions and form hydroxide ions
(OH-) are called bases. In the body there must be a
balance between the formation of hydrogen ions
and the removal of hydrogen ions for homeosta-