forms sodium lactate and carbonic acid. Eventu-
ally this forms added carbon dioxide and water.
Effects of sodium bicarbonate and
citrate on performance
High-intensity exercise can be maintained for
only short periods of time (Parry-Billings &
MacLaren 1986). Energy for this type of activity
comes predominantly from the anaerobic
glycolysis system. In this process, energy is pro-
vided in the absence of oxygen as shown in the
following equation:
Glycogen+3 ADP+3 Pi ́3 ATP+2 lactic acid
+2H 2 O
The energy for the muscle contractions then
comes from the ATP molecules which are pro-
duced. The above equation indicates that the
breakdown of glucose anaerobically results in
the formation of lactic acid, which dissociates
almost immediately at a normal physiological
pH to a lactate anion and a proton [H+] (Brooks
1985), which in turn would decrease intramuscu-
lar pH (Fletcher & Hopkins 1907; Hermansen &
Osnes 1972; Osnes & Hermansen 1972; Sahlin
et al.1978) if the H+was not buffered. High rates
of glycolysis decreases pH even further, which
eventually shuts down the contractile process
(Fuchset al.1970; Donaldson & Hermansen 1978;
Bryant-Chase & Kushmerick 1988). Force gen-
eration in isolated muscle (Mainwood &
Cechetto 1980) has also been shown to be pH sen-
sitive. More specifically, the myofibrillar protein
troponin does not bind as efficiently to calcium
when pH decreases, and this impairs the forma-
tion of the actomyosin complex (Fuchs et al.
1970). This reaction is reversible, so that when
pH is reversed, bringing it towards a normal
level, recovery of force generation takes place
(Bryant-Chase & Kushmerick 1988). Changes in
pH have also been shown to have an effect on
energy production (Hill & Lupton 1923; Hill
1955; Krebs 1964). When muscle intracellular
pH reaches 6.3, the process of glycolysis is inhib-
ited by an impairment of the activity of the gly-
colytic enzyme phosphofructokinase (Trivedi &
Danforth 1966). In order to reduce or delay
these fatigue-producing processes, the ingestion
of sodium bicarbonate has been used both ex-
perimentally and practically.
Research into acid–base balance during exer-
cise commenced many decades ago. Dennig et al.
(1931) used acid salts to make runners morebicarbonate and citrate 395
N o r m a l
Acidosis Alkalosis7.0 7.1 7.2 7.3 7.4 7.5 7.6 7.7
pH[H+] (mol–1.l)1 x 10–76 x 10–88 x 10–84 x 10–82 x 10–87.8Fig. 29.2The relationship
between [H+] and pH within the
extreme physiological range.